Maryam Tahhan [Wed, 23 Nov 2022 09:00:43 +0000 (09:00 +0000)]
docs/bpf: Add BPF_MAP_TYPE_XSKMAP documentation
Add documentation for BPF_MAP_TYPE_XSKMAP including kernel version introduced,
usage and examples.
Signed-off-by: Maryam Tahhan <mtahhan@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221123090043.83945-1-mtahhan@redhat.com
Rong Tao [Tue, 22 Nov 2022 02:32:56 +0000 (10:32 +0800)]
samples/bpf: Fix wrong allocation size in xdp_router_ipv4_user
prefix_key->data allocates three bytes using alloca(), but four bytes are
actually accessed in the program.
Signed-off-by: Rong Tao <rongtao@cestc.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/tencent_F9E2E81922B0C181D05B96DAE5AB0ACE6B06@qq.com
Rong Tao [Tue, 22 Nov 2022 00:50:42 +0000 (08:50 +0800)]
docs/bpf: Update btf selftests program and add link
Commit
c64779e24e88("selftests/bpf: Merge most of test_btf into test_progs")
renamed the BTF selftest from 'test_btf.c' to 'prog_tests/btf.c'.
Signed-off-by: Rong Tao <rongtao@cestc.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/tencent_1FA6904156E8E599CAE4ABDBE80F22830106@qq.com
Alexei Starovoitov [Thu, 24 Nov 2022 21:53:14 +0000 (13:53 -0800)]
bpf: Don't mark arguments to fentry/fexit programs as trusted.
The PTR_TRUSTED flag should only be applied to pointers where the verifier can
guarantee that such pointers are valid.
The fentry/fexit/fmod_ret programs are not in this category.
Only arguments of SEC("tp_btf") and SEC("iter") programs are trusted
(which have BPF_TRACE_RAW_TP and BPF_TRACE_ITER attach_type correspondingly)
This bug was masked because convert_ctx_accesses() was converting trusted
loads into BPF_PROBE_MEM loads. Fix it as well.
The loads from trusted pointers don't need exception handling.
Fixes:
3f00c5239344 ("bpf: Allow trusted pointers to be passed to KF_TRUSTED_ARGS kfuncs")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221124215314.55890-1-alexei.starovoitov@gmail.com
Alexei Starovoitov [Thu, 24 Nov 2022 20:27:13 +0000 (12:27 -0800)]
Merge branch 'bpf: Add bpf_rcu_read_lock() support'
Yonghong Song says:
====================
Currently, without rcu attribute info in BTF, the verifier treats
rcu tagged pointer as a normal pointer. This might be a problem
for sleepable program where rcu_read_lock()/unlock() is not available.
For example, for a sleepable fentry program, if rcu protected memory
access is interleaved with a sleepable helper/kfunc, it is possible
the memory access after the sleepable helper/kfunc might be invalid
since the object might have been freed then. Even without
a sleepable helper/kfunc, without rcu_read_lock() protection,
it is possible that the rcu protected object might be release
in the middle of bpf program execution which may cause incorrect
result.
To prevent above cases, enable btf_type_tag("rcu") attributes,
introduce new bpf_rcu_read_lock/unlock() kfuncs and add verifier support.
In the rest of patch set, Patch 1 enabled btf_type_tag for __rcu
attribute. Patche 2 added might_sleep in bpf_func_proto. Patch 3 added new
bpf_rcu_read_lock/unlock() kfuncs and verifier support.
Patch 4 added some tests for these two new kfuncs.
Changelogs:
v9 -> v10:
. if no rcu tag support in vmlinux btf, using bpf_rcu_read_lock/unlock()
will cause verification error.
. at bpf_rcu_read_unlock(), invalidate rcu ptr to PTR_UNTRUSTED
instead of SCALAR_VALUE.
. a few other comment changes and other minor changes.
v8 -> v9:
. remove sleepable prog check for ld_abs/ind checking in rcu read
lock region.
. fix a test failure with gcc-compiled kernel.
. a couple of other minor fixes.
v7 -> v8:
. add might_sleep in bpf_func_proto so we can easily identify whether
a helper is sleepable or not.
. do not enforce rcu rules for sleepable, e.g., rcu dereference must
be in a bpf_rcu_read_lock region. This is to keep old code working
fine.
. Mark 'b' in 'b = a->b' (b is tagged with __rcu) as MEM_RCU only if
'b = a->b' in rcu read region and 'a' is trusted. This adds safety
guarantee for 'b' inside the rcu read region.
v6 -> v7:
. rebase on top of bpf-next.
. remove the patch which enables sleepable program using
cgrp_local_storage map. This is orthogonal to this patch set
and will be addressed separately.
. mark the rcu pointer dereference result as UNTRUSTED if inside
a bpf_rcu_read_lock() region.
v5 -> v6:
. fix selftest prog miss_unlock which tested nested locking.
. add comments in selftest prog cgrp_succ to explain how to handle
nested memory access after rcu memory load.
v4 -> v5:
. add new test to aarch64 deny list.
v3 -> v4:
. fix selftest failures when built with gcc. gcc doesn't support
btf_type_tag yet and some tests relies on that. skip these
tests if vmlinux BTF does not have btf_type_tag("rcu").
v2 -> v3:
. went back to MEM_RCU approach with invalidate rcu ptr registers
at bpf_rcu_read_unlock() place.
. remove KF_RCU_LOCK/UNLOCK flag and compare btf_id at verification
time instead.
v1 -> v2:
. use kfunc instead of helper for bpf_rcu_read_lock/unlock.
. not use MEM_RCU bpf_type_flag, instead use active_rcu_lock
in reg state to identify rcu ptr's.
. Add more self tests.
. add new test to s390x deny list.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Yonghong Song [Thu, 24 Nov 2022 05:32:22 +0000 (21:32 -0800)]
selftests/bpf: Add tests for bpf_rcu_read_lock()
Add a few positive/negative tests to test bpf_rcu_read_lock()
and its corresponding verifier support. The new test will fail
on s390x and aarch64, so an entry is added to each of their
respective deny lists.
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221124053222.2374650-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Yonghong Song [Thu, 24 Nov 2022 05:32:17 +0000 (21:32 -0800)]
bpf: Add kfunc bpf_rcu_read_lock/unlock()
Add two kfunc's bpf_rcu_read_lock() and bpf_rcu_read_unlock(). These two kfunc's
can be used for all program types. The following is an example about how
rcu pointer are used w.r.t. bpf_rcu_read_lock()/bpf_rcu_read_unlock().
struct task_struct {
...
struct task_struct *last_wakee;
struct task_struct __rcu *real_parent;
...
};
Let us say prog does 'task = bpf_get_current_task_btf()' to get a
'task' pointer. The basic rules are:
- 'real_parent = task->real_parent' should be inside bpf_rcu_read_lock
region. This is to simulate rcu_dereference() operation. The
'real_parent' is marked as MEM_RCU only if (1). task->real_parent is
inside bpf_rcu_read_lock region, and (2). task is a trusted ptr. So
MEM_RCU marked ptr can be 'trusted' inside the bpf_rcu_read_lock region.
- 'last_wakee = real_parent->last_wakee' should be inside bpf_rcu_read_lock
region since it tries to access rcu protected memory.
- the ptr 'last_wakee' will be marked as PTR_UNTRUSTED since in general
it is not clear whether the object pointed by 'last_wakee' is valid or
not even inside bpf_rcu_read_lock region.
The verifier will reset all rcu pointer register states to untrusted
at bpf_rcu_read_unlock() kfunc call site, so any such rcu pointer
won't be trusted any more outside the bpf_rcu_read_lock() region.
The current implementation does not support nested rcu read lock
region in the prog.
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221124053217.2373910-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Yonghong Song [Thu, 24 Nov 2022 05:32:11 +0000 (21:32 -0800)]
bpf: Introduce might_sleep field in bpf_func_proto
Introduce bpf_func_proto->might_sleep to indicate a particular helper
might sleep. This will make later check whether a helper might be
sleepable or not easier.
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221124053211.2373553-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Yonghong Song [Thu, 24 Nov 2022 05:32:06 +0000 (21:32 -0800)]
compiler_types: Define __rcu as __attribute__((btf_type_tag("rcu")))
Currently, without rcu attribute info in BTF, the verifier treats
rcu tagged pointer as a normal pointer. This might be a problem
for sleepable program where rcu_read_lock()/unlock() is not available.
For example, for a sleepable fentry program, if rcu protected memory
access is interleaved with a sleepable helper/kfunc, it is possible
the memory access after the sleepable helper/kfunc might be invalid
since the object might have been freed then. To prevent such cases,
introducing rcu tagging for memory accesses in verifier can help
to reject such programs.
To enable rcu tagging in BTF, during kernel compilation,
define __rcu as attribute btf_type_tag("rcu") so __rcu information can
be preserved in dwarf and btf, and later can be used for bpf prog verification.
Acked-by: KP Singh <kpsingh@kernel.org>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221124053206.2373141-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Tue, 22 Nov 2022 14:53:00 +0000 (08:53 -0600)]
selftests/bpf: Add selftests for bpf_task_from_pid()
Add some selftest testcases that validate the expected behavior of the
bpf_task_from_pid() kfunc that was added in the prior patch.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221122145300.251210-3-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Tue, 22 Nov 2022 14:52:59 +0000 (08:52 -0600)]
bpf: Add bpf_task_from_pid() kfunc
Callers can currently store tasks as kptrs using bpf_task_acquire(),
bpf_task_kptr_get(), and bpf_task_release(). These are useful if a
caller already has a struct task_struct *, but there may be some callers
who only have a pid, and want to look up the associated struct
task_struct * from that to e.g. find task->comm.
This patch therefore adds a new bpf_task_from_pid() kfunc which allows
BPF programs to get a struct task_struct * kptr from a pid.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221122145300.251210-2-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Stanislav Fomichev [Thu, 24 Nov 2022 00:28:38 +0000 (16:28 -0800)]
bpf: Unify and simplify btf_func_proto_check error handling
Replace 'err = x; break;' with 'return x;'.
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221124002838.2700179-1-sdf@google.com
Ji Rongfeng [Fri, 18 Nov 2022 08:18:18 +0000 (16:18 +0800)]
bpf: Update bpf_{g,s}etsockopt() documentation
* append missing optnames to the end
* simplify bpf_getsockopt()'s doc
Signed-off-by: Ji Rongfeng <SikoJobs@outlook.com>
Link: https://lore.kernel.org/r/DU0P192MB15479B86200B1216EC90E162D6099@DU0P192MB1547.EURP192.PROD.OUTLOOK.COM
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Donald Hunter [Tue, 22 Nov 2022 14:39:33 +0000 (14:39 +0000)]
docs/bpf: Fix sphinx warnings in BPF map docs
Fix duplicate C declaration warnings when using sphinx >= 3.1.
Reported-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Akira Yokosawa <akiyks@gmail.com>
Link: https://lore.kernel.org/bpf/ed4dac84-1b12-5c58-e4de-93ab9ac67c09@gmail.com
Link: https://lore.kernel.org/bpf/20221122143933.91321-1-donald.hunter@gmail.com
Stanislav Fomichev [Wed, 23 Nov 2022 03:54:21 +0000 (19:54 -0800)]
selftests/bpf: Add reproducer for decl_tag in func_proto argument
It should trigger a WARN_ON_ONCE in btf_type_id_size:
RIP: 0010:btf_type_id_size+0x8bd/0x940 kernel/bpf/btf.c:1952
btf_func_proto_check kernel/bpf/btf.c:4506 [inline]
btf_check_all_types kernel/bpf/btf.c:4734 [inline]
btf_parse_type_sec+0x1175/0x1980 kernel/bpf/btf.c:4763
btf_parse kernel/bpf/btf.c:5042 [inline]
btf_new_fd+0x65a/0xb00 kernel/bpf/btf.c:6709
bpf_btf_load+0x6f/0x90 kernel/bpf/syscall.c:4342
__sys_bpf+0x50a/0x6c0 kernel/bpf/syscall.c:5034
__do_sys_bpf kernel/bpf/syscall.c:5093 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5091 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5091
do_syscall_64+0x54/0x70 arch/x86/entry/common.c:48
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221123035422.872531-1-sdf@google.com
Stanislav Fomichev [Wed, 23 Nov 2022 03:54:22 +0000 (19:54 -0800)]
bpf: Prevent decl_tag from being referenced in func_proto arg
Syzkaller managed to hit another decl_tag issue:
btf_func_proto_check kernel/bpf/btf.c:4506 [inline]
btf_check_all_types kernel/bpf/btf.c:4734 [inline]
btf_parse_type_sec+0x1175/0x1980 kernel/bpf/btf.c:4763
btf_parse kernel/bpf/btf.c:5042 [inline]
btf_new_fd+0x65a/0xb00 kernel/bpf/btf.c:6709
bpf_btf_load+0x6f/0x90 kernel/bpf/syscall.c:4342
__sys_bpf+0x50a/0x6c0 kernel/bpf/syscall.c:5034
__do_sys_bpf kernel/bpf/syscall.c:5093 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5091 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5091
do_syscall_64+0x54/0x70 arch/x86/entry/common.c:48
This seems similar to commit
ea68376c8bed ("bpf: prevent decl_tag from being
referenced in func_proto") but for the argument.
Reported-by: syzbot+8dd0551dda6020944c5d@syzkaller.appspotmail.com
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221123035422.872531-2-sdf@google.com
Donald Hunter [Wed, 23 Nov 2022 14:11:51 +0000 (14:11 +0000)]
docs/bpf: Document BPF_MAP_TYPE_BLOOM_FILTER
Add documentation for BPF_MAP_TYPE_BLOOM_FILTER including kernel
BPF helper usage, userspace usage and examples.
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/bpf/20221123141151.54556-1-donald.hunter@gmail.com
Maryam Tahhan [Wed, 23 Nov 2022 09:23:21 +0000 (09:23 +0000)]
docs/bpf: Fix sphinx warnings for devmap
Sphinx version >=3.1 warns about duplicate function declarations in the
DEVMAP documentation. This is because the function name is the same for
kernel and user space BPF progs but the parameters and return types
they take is what differs. This patch moves from using the ``c:function::``
directive to using the ``code-block:: c`` directive. The patches also fix
the indentation for the text associated with the "new" code block delcarations.
The missing support of c:namespace-push:: and c:namespace-pop:: directives by
helper scripts for kernel documentation prevents using the ``c:function::``
directive with proper namespacing.
Signed-off-by: Maryam Tahhan <mtahhan@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221123092321.88558-3-mtahhan@redhat.com
Maryam Tahhan [Wed, 23 Nov 2022 09:23:20 +0000 (09:23 +0000)]
docs/bpf: Fix sphinx warnings for cpumap
Sphinx version >=3.1 warns about duplicate function declarations in the
CPUMAP documentation. This is because the function name is the same for
kernel and user space BPF progs but the parameters and return types
they take is what differs. This patch moves from using the ``c:function::``
directive to using the ``code-block:: c`` directive. The patches also fix
the indentation for the text associated with the "new" code block delcarations.
The missing support of c:namespace-push:: and c:namespace-pop:: directives by
helper scripts for kernel documentation prevents using the ``c:function::``
directive with proper namespacing.
Signed-off-by: Maryam Tahhan <mtahhan@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221123092321.88558-2-mtahhan@redhat.com
Donald Hunter [Mon, 21 Nov 2022 12:17:34 +0000 (12:17 +0000)]
docs/bpf: Add table of BPF program types to libbpf docs
Extend the libbpf documentation with a table of program types,
attach points and ELF section names.
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20221121121734.98329-1-donald.hunter@gmail.com
Yonghong Song [Wed, 23 Nov 2022 15:57:59 +0000 (07:57 -0800)]
bpf: Fix a BTF_ID_LIST bug with CONFIG_DEBUG_INFO_BTF not set
With CONFIG_DEBUG_INFO_BTF not set, we hit the following compilation error,
/.../kernel/bpf/verifier.c:8196:23: error: array index 6 is past the end of the array
(that has type 'u32[5]' (aka 'unsigned int[5]')) [-Werror,-Warray-bounds]
if (meta->func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx])
^ ~~~~~~~~~~~~~~~~~~~~~~~
/.../kernel/bpf/verifier.c:8174:1: note: array 'special_kfunc_list' declared here
BTF_ID_LIST(special_kfunc_list)
^
/.../include/linux/btf_ids.h:207:27: note: expanded from macro 'BTF_ID_LIST'
#define BTF_ID_LIST(name) static u32 __maybe_unused name[5];
^
/.../kernel/bpf/verifier.c:8443:19: error: array index 5 is past the end of the array
(that has type 'u32[5]' (aka 'unsigned int[5]')) [-Werror,-Warray-bounds]
btf_id == special_kfunc_list[KF_bpf_list_pop_back];
^ ~~~~~~~~~~~~~~~~~~~~
/.../kernel/bpf/verifier.c:8174:1: note: array 'special_kfunc_list' declared here
BTF_ID_LIST(special_kfunc_list)
^
/.../include/linux/btf_ids.h:207:27: note: expanded from macro 'BTF_ID_LIST'
#define BTF_ID_LIST(name) static u32 __maybe_unused name[5];
...
Fix the problem by increase the size of BTF_ID_LIST to 16 to avoid compilation error
and also prevent potentially unintended issue due to out-of-bound access.
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221123155759.2669749-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Stanislav Fomichev [Wed, 23 Nov 2022 20:08:29 +0000 (12:08 -0800)]
selftests/bpf: Mount debugfs in setns_by_fd
Jiri reports broken test_progs after recent commit
68f8e3d4b916
("selftests/bpf: Make sure zero-len skbs aren't redirectable").
Apparently we don't remount debugfs when we switch back networking namespace.
Let's explicitly mount /sys/kernel/debug.
0: https://lore.kernel.org/bpf/
63b85917-a2ea-8e35-620c-
808560910819@meta.com/T/#ma66ca9c92e99eee0a25e40f422489b26ee0171c1
Fixes:
a30338840fa5 ("selftests/bpf: Move open_netns() and close_netns() into network_helpers.c")
Reported-by: Jiri Olsa <olsajiri@gmail.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20221123200829.2226254-1-sdf@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Wed, 23 Nov 2022 13:52:53 +0000 (07:52 -0600)]
bpf: Don't use idx variable when registering kfunc dtors
In commit
fda01efc6160 ("bpf: Enable cgroups to be used as kptrs"), I
added an 'int idx' variable to kfunc_init() which was meant to
dynamically set the index of the btf id entries of the
'generic_dtor_ids' array. This was done to make the code slightly less
brittle as the struct cgroup * kptr kfuncs such as bpf_cgroup_aquire()
are compiled out if CONFIG_CGROUPS is not defined. This, however, causes
an lkp build warning:
>> kernel/bpf/helpers.c:2005:40: warning: multiple unsequenced
modifications to 'idx' [-Wunsequenced]
.btf_id = generic_dtor_ids[idx++],
Fix the warning by just hard-coding the indices.
Fixes:
fda01efc6160 ("bpf: Enable cgroups to be used as kptrs")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: David Vernet <void@manifault.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221123135253.637525-1-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Alexei Starovoitov [Tue, 22 Nov 2022 22:45:41 +0000 (14:45 -0800)]
Merge branch 'Support storing struct cgroup * objects as kptrs'
David Vernet says:
====================
In [0], we added support for storing struct task_struct * objects as
kptrs. This patch set extends this effort to also include storing struct
cgroup * object as kptrs.
As with tasks, there are many possible use cases for storing cgroups in
maps. During tracing, for example, it could be useful to query cgroup
statistics such as PSI averages, or tracking which tasks are migrating
to and from the cgroup.
[0]: https://lore.kernel.org/all/
20221120051004.3605026-1-void@manifault.com/
====================
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Tue, 22 Nov 2022 05:54:58 +0000 (23:54 -0600)]
selftests/bpf: Add selftests for bpf_cgroup_ancestor() kfunc
bpf_cgroup_ancestor() allows BPF programs to access the ancestor of a
struct cgroup *. This patch adds selftests that validate its expected
behavior.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221122055458.173143-5-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Tue, 22 Nov 2022 05:54:57 +0000 (23:54 -0600)]
bpf: Add bpf_cgroup_ancestor() kfunc
struct cgroup * objects have a variably sized struct cgroup *ancestors[]
field which stores pointers to their ancestor cgroups. If using a cgroup
as a kptr, it can be useful to access these ancestors, but doing so
requires variable offset accesses for PTR_TO_BTF_ID, which is currently
unsupported.
This is a very useful field to access for cgroup kptrs, as programs may
wish to walk their ancestor cgroups when determining e.g. their
proportional cpu.weight. So as to enable this functionality with cgroup
kptrs before var_off is supported for PTR_TO_BTF_ID, this patch adds a
bpf_cgroup_ancestor() kfunc which accesses the cgroup node on behalf of
the caller, and acquires a reference on it. Once var_off is supported
for PTR_TO_BTF_ID, and fields inside a struct can be marked as trusted
so they retain the PTR_TRUSTED modifier when walked, this can be
removed.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221122055458.173143-4-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Tue, 22 Nov 2022 05:54:56 +0000 (23:54 -0600)]
selftests/bpf: Add cgroup kfunc / kptr selftests
This patch adds a selftest suite to validate the cgroup kfuncs that were
added in the prior patch.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221122055458.173143-3-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Tue, 22 Nov 2022 05:54:55 +0000 (23:54 -0600)]
bpf: Enable cgroups to be used as kptrs
Now that tasks can be used as kfuncs, and the PTR_TRUSTED flag is
available for us to easily add basic acquire / get / release kfuncs, we
can do the same for cgroups. This patch set adds the following kfuncs
which enable using cgroups as kptrs:
struct cgroup *bpf_cgroup_acquire(struct cgroup *cgrp);
struct cgroup *bpf_cgroup_kptr_get(struct cgroup **cgrpp);
void bpf_cgroup_release(struct cgroup *cgrp);
A follow-on patch will add a selftest suite which validates these
kfuncs.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221122055458.173143-2-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Alexei Starovoitov [Tue, 22 Nov 2022 17:15:29 +0000 (09:15 -0800)]
selftests/bpf: Workaround for llvm nop-4 bug
Currently LLVM fails to recognize .data.* as data section and defaults to .text
section. Later BPF backend tries to emit 4-byte NOP instruction which doesn't
exist in BPF ISA and aborts.
The fix for LLVM is pending:
https://reviews.llvm.org/D138477
While waiting for the fix lets workaround the linked_list test case
by using .bss.* prefix which is properly recognized by LLVM as BSS section.
Fix libbpf to support .bss. prefix and adjust tests.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Alexei Starovoitov [Tue, 22 Nov 2022 16:50:04 +0000 (08:50 -0800)]
Revert "selftests/bpf: Temporarily disable linked list tests"
This reverts commit
0a2f85a1be4328d29aefa54684d10c23a3298fef.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Stanislav Fomichev [Mon, 21 Nov 2022 18:03:40 +0000 (10:03 -0800)]
selftests/bpf: Make sure zero-len skbs aren't redirectable
LWT_XMIT to test L3 case, TC to test L2 case.
v2:
- s/veth_ifindex/ipip_ifindex/ in two places (Martin)
- add comment about which condition triggers the rejection (Martin)
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20221121180340.1983627-2-sdf@google.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Stanislav Fomichev [Mon, 21 Nov 2022 18:03:39 +0000 (10:03 -0800)]
bpf: Move skb->len == 0 checks into __bpf_redirect
To avoid potentially breaking existing users.
Both mac/no-mac cases have to be amended; mac_header >= network_header
is not enough (verified with a new test, see next patch).
Fixes:
fd1894224407 ("bpf: Don't redirect packets with invalid pkt_len")
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20221121180340.1983627-1-sdf@google.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Hou Tao [Mon, 21 Nov 2022 07:34:40 +0000 (15:34 +0800)]
selftests/bpf: Add test for cgroup iterator on a dead cgroup
The test closes both iterator link fd and cgroup fd, and removes the
cgroup file to make a dead cgroup before reading from cgroup iterator.
It also uses kern_sync_rcu() and usleep() to wait for the release of
start cgroup. If the start cgroup is not pinned by cgroup iterator,
reading from iterator fd will trigger use-after-free.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/bpf/20221121073440.1828292-4-houtao@huaweicloud.com
Hou Tao [Mon, 21 Nov 2022 07:34:39 +0000 (15:34 +0800)]
selftests/bpf: Add cgroup helper remove_cgroup()
Add remove_cgroup() to remove a cgroup which doesn't have any children
or live processes. It will be used by the following patch to test cgroup
iterator on a dead cgroup.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221121073440.1828292-3-houtao@huaweicloud.com
Hou Tao [Mon, 21 Nov 2022 07:34:38 +0000 (15:34 +0800)]
bpf: Pin the start cgroup in cgroup_iter_seq_init()
bpf_iter_attach_cgroup() has already acquired an extra reference for the
start cgroup, but the reference may be released if the iterator link fd
is closed after the creation of iterator fd, and it may lead to
user-after-free problem when reading the iterator fd.
An alternative fix is pinning iterator link when opening iterator,
but it will make iterator link being still visible after the close of
iterator link fd and the behavior is different with other link types, so
just fixing it by acquiring another reference for the start cgroup.
Fixes:
d4ccaf58a847 ("bpf: Introduce cgroup iter")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221121073440.1828292-2-houtao@huaweicloud.com
Kees Cook [Fri, 18 Nov 2022 18:34:14 +0000 (10:34 -0800)]
bpf/verifier: Use kmalloc_size_roundup() to match ksize() usage
Most allocation sites in the kernel want an explicitly sized allocation
(and not "more"), and that dynamic runtime analysis tools (e.g. KASAN,
UBSAN_BOUNDS, FORTIFY_SOURCE, etc) are looking for precise bounds checking
(i.e. not something that is rounded up). A tiny handful of allocations
were doing an implicit alloc/realloc loop that actually depended on
ksize(), and didn't actually always call realloc. This has created a
long series of bugs and problems over many years related to the runtime
bounds checking, so these callers are finally being adjusted to _not_
depend on the ksize() side-effect, by doing one of several things:
- tracking the allocation size precisely and just never calling ksize()
at all [1].
- always calling realloc and not using ksize() at all. (This solution
ends up actually be a subset of the next solution.)
- using kmalloc_size_roundup() to explicitly round up the desired
allocation size immediately [2].
The bpf/verifier case is this another of this latter case, and is the
last outstanding case to be fixed in the kernel.
Because some of the dynamic bounds checking depends on the size being an
_argument_ to an allocator function (i.e. see the __alloc_size attribute),
the ksize() users are rare, and it could waste local variables, it
was been deemed better to explicitly separate the rounding up from the
allocation itself [3].
Round up allocations with kmalloc_size_roundup() so that the verifier's
use of ksize() is always accurate.
[1] e.g.:
https://git.kernel.org/linus/
712f210a457d
https://git.kernel.org/linus/
72c08d9f4c72
[2] e.g.:
https://git.kernel.org/netdev/net-next/c/
12d6c1d3a2ad
https://git.kernel.org/netdev/net-next/c/
ab3f7828c979
https://git.kernel.org/netdev/net-next/c/
d6dd508080a3
[3] https://lore.kernel.org/lkml/
0ea1fc165a6c6117f982f4f135093e69cb884930.camel@redhat.com/
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20221118183409.give.387-kees@kernel.org
Alexei Starovoitov [Mon, 21 Nov 2022 00:17:46 +0000 (16:17 -0800)]
Merge branch 'clean-up bpftool from legacy support'
Sahid Orentino Ferdjaoui says:
====================
As part of commit
93b8952d223a ("libbpf: deprecate legacy BPF map
definitions") and commit
bd054102a8c7 ("libbpf: enforce strict libbpf
1.0 behaviors") The --legacy option is not relevant anymore. #1 is
removing it. #4 is cleaning the code from using libbpf_get_error().
About patches #2 and #3 They are changes discovered while working on
this series (credits to Quentin Monnet). #2 is cleaning-up usage of an
unnecessary PTR_ERR(NULL), finally #3 is fixing an invalid value
passed to strerror().
v1 -> v2:
- Addressed review comments from Yonghong Song on patch #4
- Added a patch #5 that removes unwanted function noticed by
Yonghong Song
v2 -> v3
- Addressed review comments from Andrii Nakryiko on patch #2, #3, #4
* clean-up usage of libbpf_get_error() (#2, #3)
* fix possible return of an uninitialized local variable err
* fix returned errors using errno
v3 -> v4
- Addressed review comments from Quentin Monnet
* fix line moved from patch #2 to patch #3
* fix missing returned errors using errno
* fix some returned values to errno instead of -1
====================
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Sahid Orentino Ferdjaoui [Sun, 20 Nov 2022 11:26:43 +0000 (11:26 +0000)]
bpftool: remove function free_btf_vmlinux()
The function contains a single btf__free() call which can be
inlined. Credits to Yonghong Song.
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@industrialdiscipline.com>
Acked-by: Yonghong Song <yhs@fb.com>
Suggested-by: Yonghong Song <yhs@fb.com>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20221120112515.38165-6-sahid.ferdjaoui@industrialdiscipline.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Sahid Orentino Ferdjaoui [Sun, 20 Nov 2022 11:26:32 +0000 (11:26 +0000)]
bpftool: clean-up usage of libbpf_get_error()
bpftool is now totally compliant with libbpf 1.0 mode and is not
expected to be compiled with pre-1.0, let's clean-up the usage of
libbpf_get_error().
The changes stay aligned with returned errors always negative.
- In tools/bpf/bpftool/btf.c This fixes an uninitialized local
variable `err` in function do_dump() because it may now be returned
without having been set.
- This also removes the checks on NULL pointers before calling
btf__free() because that function already does the check.
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@industrialdiscipline.com>
Link: https://lore.kernel.org/r/20221120112515.38165-5-sahid.ferdjaoui@industrialdiscipline.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Sahid Orentino Ferdjaoui [Sun, 20 Nov 2022 11:26:18 +0000 (11:26 +0000)]
bpftool: fix error message when function can't register struct_ops
It is expected that errno be passed to strerror(). This also cleans
this part of code from using libbpf_get_error().
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@industrialdiscipline.com>
Acked-by: Yonghong Song <yhs@fb.com>
Suggested-by: Quentin Monnet <quentin@isovalent.com>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20221120112515.38165-4-sahid.ferdjaoui@industrialdiscipline.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Sahid Orentino Ferdjaoui [Sun, 20 Nov 2022 11:26:07 +0000 (11:26 +0000)]
bpftool: replace return value PTR_ERR(NULL) with 0
There is no reasons to keep PTR_ERR() when kern_btf=NULL, let's just
return 0.
This also cleans this part of code from using libbpf_get_error().
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@industrialdiscipline.com>
Acked-by: Yonghong Song <yhs@fb.com>
Suggested-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20221120112515.38165-3-sahid.ferdjaoui@industrialdiscipline.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Sahid Orentino Ferdjaoui [Sun, 20 Nov 2022 11:25:55 +0000 (11:25 +0000)]
bpftool: remove support of --legacy option for bpftool
Following:
commit
bd054102a8c7 ("libbpf: enforce strict libbpf 1.0 behaviors")
commit
93b8952d223a ("libbpf: deprecate legacy BPF map definitions")
The --legacy option is no longer relevant as libbpf no longer supports
it. libbpf_set_strict_mode() is a no-op operation.
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@industrialdiscipline.com>
Acked-by: Yonghong Song <yhs@fb.com>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20221120112515.38165-2-sahid.ferdjaoui@industrialdiscipline.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Alexei Starovoitov [Sun, 20 Nov 2022 23:43:37 +0000 (15:43 -0800)]
Merge branch 'bpf: Implement two type cast kfuncs'
Yonghong Song says:
====================
Currenty, a non-tracing bpf program typically has a single 'context' argument
with predefined uapi struct type. Following these uapi struct, user is able
to access other fields defined in uapi header. Inside the kernel, the
user-seen 'context' argument is replaced with 'kernel context' (or 'kctx'
in short) which can access more information than what uapi header provides.
To access other info not in uapi header, people typically do two things:
(1). extend uapi to access more fields rooted from 'context'.
(2). use bpf_probe_read_kernl() helper to read particular field based on
kctx.
Using (1) needs uapi change and using (2) makes code more complex since
direct memory access is not allowed.
There are already a few instances trying to access more information from
kctx:
. trying to access some fields from perf_event kctx ([1]).
. trying to access some fields from xdp kctx ([2]).
This patch set tried to allow direct memory access for kctx fields
by introducing bpf_cast_to_kern_ctx() kfunc.
Martin mentioned a use case like type casting below:
#define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
basically a 'unsigned char *" casted to 'struct skb_shared_info *'. This patch
set tries to support such a use case as well with bpf_rdonly_cast().
For the patch series, Patch 1 added support for a kfunc available to all
prog types. Patch 2 added bpf_cast_to_kern_ctx() kfunc. Patch 3 added
bpf_rdonly_cast() kfunc. Patch 4 added a few positive and negative tests.
[1] https://lore.kernel.org/bpf/
ad15b398-9069-4a0e-48cb-
4bb651ec3088@meta.com/
[2] https://lore.kernel.org/bpf/
20221109215242.1279993-1-john.fastabend@gmail.com/
Changelog:
v3 -> v4:
- remove unnecessary bpf_ctx_convert.t error checking
- add and use meta.ret_btf_id instead of meta.arg_constant.value for
bpf_cast_to_kern_ctx().
- add PTR_TRUSTED to the return PTR_TO_BTF_ID type for bpf_cast_to_kern_ctx().
v2 -> v3:
- rebase on top of bpf-next (for merging conflicts)
- add the selftest to s390x deny list
rfcv1 -> v2:
- break original one kfunc into two.
- add missing error checks and error logs.
- adapt to the new conventions in
https://lore.kernel.org/all/
20221118015614.2013203-1-memxor@gmail.com/
for example, with __ign and __k suffix.
- added support in fixup_kfunc_call() to replace kfunc calls with a single mov.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Yonghong Song [Sun, 20 Nov 2022 19:54:42 +0000 (11:54 -0800)]
bpf: Add type cast unit tests
Three tests are added. One is from John Fastabend ({1]) which tests
tracing style access for xdp program from the kernel ctx.
Another is a tc test to test both kernel ctx tracing style access
and explicit non-ctx type cast. The third one is for negative tests
including two tests, a tp_bpf test where the bpf_rdonly_cast()
returns a untrusted ptr which cannot be used as helper argument,
and a tracepoint test where the kernel ctx is a u64.
Also added the test to DENYLIST.s390x since s390 does not currently
support calling kernel functions in JIT mode.
[1] https://lore.kernel.org/bpf/
20221109215242.1279993-1-john.fastabend@gmail.com/
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195442.3114844-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Yonghong Song [Sun, 20 Nov 2022 19:54:37 +0000 (11:54 -0800)]
bpf: Add a kfunc for generic type cast
Implement bpf_rdonly_cast() which tries to cast the object
to a specified type. This tries to support use case like below:
#define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
where skb_end_pointer(SKB) is a 'unsigned char *' and needs to
be casted to 'struct skb_shared_info *'.
The signature of bpf_rdonly_cast() looks like
void *bpf_rdonly_cast(void *obj, __u32 btf_id)
The function returns the same 'obj' but with PTR_TO_BTF_ID with
btf_id. The verifier will ensure btf_id being a struct type.
Since the supported type cast may not reflect what the 'obj'
represents, the returned btf_id is marked as PTR_UNTRUSTED, so
the return value and subsequent pointer chasing cannot be
used as helper/kfunc arguments.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195437.3114585-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Yonghong Song [Sun, 20 Nov 2022 19:54:32 +0000 (11:54 -0800)]
bpf: Add a kfunc to type cast from bpf uapi ctx to kernel ctx
Implement bpf_cast_to_kern_ctx() kfunc which does a type cast
of a uapi ctx object to the corresponding kernel ctx. Previously
if users want to access some data available in kctx but not
in uapi ctx, bpf_probe_read_kernel() helper is needed.
The introduction of bpf_cast_to_kern_ctx() allows direct
memory access which makes code simpler and easier to understand.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195432.3113982-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Yonghong Song [Sun, 20 Nov 2022 19:54:26 +0000 (11:54 -0800)]
bpf: Add support for kfunc set with common btf_ids
Later on, we will introduce kfuncs bpf_cast_to_kern_ctx() and
bpf_rdonly_cast() which apply to all program types. Currently kfunc set
only supports individual prog types. This patch added support for kfunc
applying to all program types.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195426.3113828-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Sun, 20 Nov 2022 21:26:10 +0000 (02:56 +0530)]
bpf: Disallow bpf_obj_new_impl call when bpf_mem_alloc_init fails
In the unlikely event that bpf_global_ma is not correctly initialized,
instead of checking the boolean everytime bpf_obj_new_impl is called,
simply check it while loading the program and return an error if
bpf_global_ma_set is false.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221120212610.2361700-1-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Alexei Starovoitov [Sun, 20 Nov 2022 17:16:21 +0000 (09:16 -0800)]
Merge branch 'Support storing struct task_struct objects as kptrs'
David Vernet says:
====================
Now that BPF supports adding new kernel functions with kfuncs, and
storing kernel objects in maps with kptrs, we can add a set of kfuncs
which allow struct task_struct objects to be stored in maps as
referenced kptrs.
The possible use cases for doing this are plentiful. During tracing,
for example, it would be useful to be able to collect some tasks that
performed a certain operation, and then periodically summarize who they
are, which cgroup they're in, how much CPU time they've utilized, etc.
Doing this now would require storing the tasks' pids along with some
relevant data to be exported to user space, and later associating the
pids to tasks in other event handlers where the data is recorded.
Another useful by-product of this is that it allows a program to pin a
task in a BPF program, and by proxy therefore also e.g. pin its task
local storage.
In order to support this, we'll need to expand KF_TRUSTED_ARGS to
support receiving trusted, non-refcounted pointers. It currently only
supports either PTR_TO_CTX pointers, or refcounted pointers. What this
means in terms of the implementation is that check_kfunc_args() would
have to also check for the PTR_TRUSTED or MEM_ALLOC type modifiers when
determining if a trusted KF_ARG_PTR_TO_ALLOC_BTF_ID or
KF_ARG_PTR_TO_BTF_ID pointer requires a refcount.
Note that PTR_UNTRUSTED is insufficient for this purpose, as it does not
cover all of the possible types of potentially unsafe pointers. For
example, a pointer obtained from walking a struct is not PTR_UNTRUSTED.
To account for this and enable us to expand KF_TRUSTED_ARGS to include
allow-listed arguments such as those passed by the kernel to tracepoints
and struct_ops callbacks, this patch set also introduces a new
PTR_TRUSTED type flag modifier which records if a pointer was obtained
passed from the kernel in a trusted context.
Currently, both PTR_TRUSTED and MEM_ALLOC are used to imply that a
pointer is trusted. Longer term, PTR_TRUSTED should be the sole source
of truth for whether a pointer is trusted. This requires us to set
PTR_TRUSTED when appropriate (e.g. when setting MEM_ALLOC), and unset it
when appropriate (e.g. when setting PTR_UNTRUSTED). We don't do that in
this patch, as we need to do more clean up before this can be done in a
clear and well-defined manner.
In closing, this patch set:
1. Adds the new PTR_TRUSTED register type modifier flag, and updates the
verifier and existing selftests accordingly. Also expands
KF_TRUSTED_ARGS to also include trusted pointers that were not obtained
from walking structs.
2. Adds a new set of kfuncs that allows struct task_struct* objects to be
used as kptrs.
3. Adds a new selftest suite to validate these new task kfuncs.
---
Changelog:
v8 -> v9:
- Moved check for release register back to where we check for
!PTR_TO_BTF_ID || socket. Change the verifier log message to
reflect really what's being tested (the presence of unsafe
modifiers) (Alexei)
- Fix verifier_test error tests to reflect above changes
- Remove unneeded parens around bitwise operator checks (Alexei)
- Move updates to reg_type_str() which allow multiple type modifiers
to be present in the prefix string, to a separate patch (Alexei)
- Increase TYPE_STR_BUF_LEN size to 128 to reflect larger prefix size
in reg_type_str().
v7 -> v8:
- Rebased onto Kumar's latest patch set which, adds a new MEM_ALLOC reg
type modifier for bpf_obj_new() calls.
- Added comments to bpf_task_kptr_get() describing some of the subtle
races we're protecting against (Alexei and John)
- Slightly rework process_kf_arg_ptr_to_btf_id(), and add a new
reg_has_unsafe_modifiers() function which validates that a register
containing a kfunc release arg doesn't have unsafe modifiers. Note
that this is slightly different than the check for KF_TRUSTED_ARGS.
An alternative here would be to treat KF_RELEASE as implicitly
requiring KF_TRUSTED_ARGS.
- Export inline bpf_type_has_unsafe_modifiers() function from
bpf_verifier.h so that it can be used from bpf_tcp_ca.c. Eventually this
function should likely be changed to bpf_type_is_trusted(), once
PTR_TRUSTED is the real source of truth.
v6 -> v7:
- Removed the PTR_WALKED type modifier, and instead define a new
PTR_TRUSTED type modifier which is set on registers containing
pointers passed from trusted contexts (i.e. as tracepoint or
struct_ops callback args) (Alexei)
- Remove the new KF_OWNED_ARGS kfunc flag. This can be accomplished
by defining a new type that wraps an existing type, such as with
struct nf_conn___init (Alexei)
- Add a test_task_current_acquire_release testcase which verifies we can
acquire a task struct returned from bpf_get_current_task_btf().
- Make bpf_task_acquire() no longer return NULL, as it can no longer be
called with a NULL task.
- Removed unnecessary is_test_kfunc_task() checks from failure
testcases.
v5 -> v6:
- Add a new KF_OWNED_ARGS kfunc flag which may be used by kfuncs to
express that they require trusted, refcounted args (Kumar)
- Rename PTR_NESTED -> PTR_WALKED in the verifier (Kumar)
- Convert reg_type_str() prefixes to use snprintf() instead of strncpy()
(Kumar)
- Add PTR_TO_BTF_ID | PTR_WALKED to missing struct btf_reg_type
instances -- specifically btf_id_sock_common_types, and
percpu_btf_ptr_types.
- Add a missing PTR_TO_BTF_ID | PTR_WALKED switch case entry in
check_func_arg_reg_off(), which is required when validating helper
calls (Kumar)
- Update reg_type_mismatch_ok() to check base types for the registers
(i.e. to accommodate type modifiers). Additionally, add a lengthy
comment that explains why this is being done (Kumar)
- Update convert_ctx_accesses() to also issue probe reads for
PTR_TO_BTF_ID | PTR_WALKED (Kumar)
- Update selftests to expect new prefix reg type strings.
- Rename task_kfunc_acquire_trusted_nested testcase to
task_kfunc_acquire_trusted_walked, and fix a comment (Kumar)
- Remove KF_TRUSTED_ARGS from bpf_task_release(), which already includes
KF_RELEASE (Kumar)
- Add bpf-next in patch subject lines (Kumar)
v4 -> v5:
- Fix an improperly formatted patch title.
v3 -> v4:
- Remove an unnecessary check from my repository that I forgot to remove
after debugging something.
v2 -> v3:
- Make bpf_task_acquire() check for NULL, and include KF_RET_NULL
(Martin)
- Include new PTR_NESTED register modifier type flag which specifies
whether a pointer was obtained from walking a struct. Use this to
expand the meaning of KF_TRUSTED_ARGS to include trusted pointers that
were passed from the kernel (Kumar)
- Add more selftests to the task_kfunc selftest suite which verify that
you cannot pass a walked pointer to bpf_task_acquire().
- Update bpf_task_acquire() to also specify KF_TRUSTED_ARGS.
v1 -> v2:
- Rename tracing_btf_ids to generic_kfunc_btf_ids, and add the new
kfuncs to that list instead of making a separate btf id list (Alexei).
- Don't run the new selftest suite on s390x, which doesn't appear to
support invoking kfuncs.
- Add a missing __diag_ignore block for -Wmissing-prototypes
(lkp@intel.com).
- Fix formatting on some of the SPDX-License-Identifier tags.
- Clarified the function header comment a bit on bpf_task_kptr_get().
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Sun, 20 Nov 2022 05:10:04 +0000 (23:10 -0600)]
bpf/selftests: Add selftests for new task kfuncs
A previous change added a series of kfuncs for storing struct
task_struct objects as referenced kptrs. This patch adds a new
task_kfunc test suite for validating their expected behavior.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221120051004.3605026-5-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Sun, 20 Nov 2022 05:10:03 +0000 (23:10 -0600)]
bpf: Add kfuncs for storing struct task_struct * as a kptr
Now that BPF supports adding new kernel functions with kfuncs, and
storing kernel objects in maps with kptrs, we can add a set of kfuncs
which allow struct task_struct objects to be stored in maps as
referenced kptrs. The possible use cases for doing this are plentiful.
During tracing, for example, it would be useful to be able to collect
some tasks that performed a certain operation, and then periodically
summarize who they are, which cgroup they're in, how much CPU time
they've utilized, etc.
In order to enable this, this patch adds three new kfuncs:
struct task_struct *bpf_task_acquire(struct task_struct *p);
struct task_struct *bpf_task_kptr_get(struct task_struct **pp);
void bpf_task_release(struct task_struct *p);
A follow-on patch will add selftests validating these kfuncs.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221120051004.3605026-4-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Sun, 20 Nov 2022 05:10:02 +0000 (23:10 -0600)]
bpf: Allow trusted pointers to be passed to KF_TRUSTED_ARGS kfuncs
Kfuncs currently support specifying the KF_TRUSTED_ARGS flag to signal
to the verifier that it should enforce that a BPF program passes it a
"safe", trusted pointer. Currently, "safe" means that the pointer is
either PTR_TO_CTX, or is refcounted. There may be cases, however, where
the kernel passes a BPF program a safe / trusted pointer to an object
that the BPF program wishes to use as a kptr, but because the object
does not yet have a ref_obj_id from the perspective of the verifier, the
program would be unable to pass it to a KF_ACQUIRE | KF_TRUSTED_ARGS
kfunc.
The solution is to expand the set of pointers that are considered
trusted according to KF_TRUSTED_ARGS, so that programs can invoke kfuncs
with these pointers without getting rejected by the verifier.
There is already a PTR_UNTRUSTED flag that is set in some scenarios,
such as when a BPF program reads a kptr directly from a map
without performing a bpf_kptr_xchg() call. These pointers of course can
and should be rejected by the verifier. Unfortunately, however,
PTR_UNTRUSTED does not cover all the cases for safety that need to
be addressed to adequately protect kfuncs. Specifically, pointers
obtained by a BPF program "walking" a struct are _not_ considered
PTR_UNTRUSTED according to BPF. For example, say that we were to add a
kfunc called bpf_task_acquire(), with KF_ACQUIRE | KF_TRUSTED_ARGS, to
acquire a struct task_struct *. If we only used PTR_UNTRUSTED to signal
that a task was unsafe to pass to a kfunc, the verifier would mistakenly
allow the following unsafe BPF program to be loaded:
SEC("tp_btf/task_newtask")
int BPF_PROG(unsafe_acquire_task,
struct task_struct *task,
u64 clone_flags)
{
struct task_struct *acquired, *nested;
nested = task->last_wakee;
/* Would not be rejected by the verifier. */
acquired = bpf_task_acquire(nested);
if (!acquired)
return 0;
bpf_task_release(acquired);
return 0;
}
To address this, this patch defines a new type flag called PTR_TRUSTED
which tracks whether a PTR_TO_BTF_ID pointer is safe to pass to a
KF_TRUSTED_ARGS kfunc or a BPF helper function. PTR_TRUSTED pointers are
passed directly from the kernel as a tracepoint or struct_ops callback
argument. Any nested pointer that is obtained from walking a PTR_TRUSTED
pointer is no longer PTR_TRUSTED. From the example above, the struct
task_struct *task argument is PTR_TRUSTED, but the 'nested' pointer
obtained from 'task->last_wakee' is not PTR_TRUSTED.
A subsequent patch will add kfuncs for storing a task kfunc as a kptr,
and then another patch will add selftests to validate.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221120051004.3605026-3-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
David Vernet [Sun, 20 Nov 2022 05:10:01 +0000 (23:10 -0600)]
bpf: Allow multiple modifiers in reg_type_str() prefix
reg_type_str() in the verifier currently only allows a single register
type modifier to be present in the 'prefix' string which is eventually
stored in the env type_str_buf. This currently works fine because there
are no overlapping type modifiers, but once PTR_TRUSTED is added, that
will no longer be the case. This patch updates reg_type_str() to support
having multiple modifiers in the prefix string, and updates the size of
type_str_buf to be 128 bytes.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221120051004.3605026-2-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tiezhu Yang [Fri, 18 Nov 2022 09:50:01 +0000 (17:50 +0800)]
bpf, samples: Use "grep -E" instead of "egrep"
The latest version of grep (3.8+) claims the egrep is now obsolete so the
build now contains warnings that look like:
egrep: warning: egrep is obsolescent; using grep -E
Fix this up by moving the related file to use "grep -E" instead.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/1668765001-12477-1-git-send-email-yangtiezhu@loongson.cn
Maryam Tahhan [Tue, 15 Nov 2022 14:49:21 +0000 (09:49 -0500)]
bpf, docs: DEVMAPs and XDP_REDIRECT
Add documentation for BPF_MAP_TYPE_DEVMAP and BPF_MAP_TYPE_DEVMAP_HASH
including kernel version introduced, usage and examples.
Add documentation that describes XDP_REDIRECT.
Signed-off-by: Maryam Tahhan <mtahhan@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221115144921.165483-1-mtahhan@redhat.com
Andrii Nakryiko [Thu, 17 Nov 2022 19:28:24 +0000 (11:28 -0800)]
libbpf: Ignore hashmap__find() result explicitly in btf_dump
Coverity is reporting that btf_dump_name_dups() doesn't check return
result of hashmap__find() call. This is intentional, so make it explicit
with (void) cast.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221117192824.4093553-1-andrii@kernel.org
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 18:59:38 +0000 (00:29 +0530)]
selftests/bpf: Skip spin lock failure test on s390x
Instead of adding the whole test to DENYLIST.s390x, which also has
success test cases that should be run, just skip over failure test
cases in case the JIT does not support kfuncs.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118185938.2139616-3-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Alexei Starovoitov [Fri, 18 Nov 2022 03:11:34 +0000 (19:11 -0800)]
Merge branch 'Allocated objects, BPF linked lists'
Kumar Kartikeya Dwivedi says:
====================
This series introduces user defined BPF objects of a type in program
BTF. This allows BPF programs to allocate their own objects, build their
own object hierarchies, and use the basic building blocks provided by
BPF runtime to build their own data structures flexibly.
Then, we introduce the support for single ownership BPF linked lists,
which can be put inside BPF maps, or allocated objects, and hold such
allocated objects as elements. It works as an instrusive collection,
which is done to allow making allocated objects part of multiple data
structures at the same time in the future.
The eventual goal of this and future patches is to allow one to do some
limited form of kernel style programming in BPF C, and allow programmers
to build their own complex data structures flexibly out of basic
building blocks.
The key difference will be that such programs are verified to be safe,
preserve runtime integrity of the system, and are proven to be bug free
as far as the invariants of BPF specific APIs are concerned.
One immediate use case that will be using the entire infrastructure this
series is introducing will be managing percpu NMI safe linked lists
inside BPF programs.
The other use case this will serve in the near future will be linking
kernel structures like XDP frame and sk_buff directly into user data
structures (rbtree, pifomap, etc.) for packet queueing. This will follow
single ownership concept included in this series.
The user has complete control of the internal locking, and hence also
the batching of operations for each critical section.
The features are:
- Allocated objects.
- bpf_obj_new, bpf_obj_drop to allocate and free them.
- Single ownership BPF linked lists.
- Support for them in BPF maps.
- Support for them in allocated objects.
- Global spin locks.
- Spin locks inside allocated objects.
Some other notable things:
- Completely static verification of locking.
- Kfunc argument handling has been completely reworked.
- Argument rewriting support for kfuncs.
- A new bpf_experimental.h header as a dumping ground for these APIs.
Any functionality exposed in this series is NOT part of UAPI. It is only
available through use of kfuncs, and structs that can be added to map
value may also change their size or name in the future. Hence, every
feature in this series must be considered experimental.
Follow-ups:
-----------
* Support for kptrs (local and kernel) in local storage and percpu maps + kptr tests
* Fixes for helper access checks rebasing on top of this series
Next steps:
-----------
* NMI safe percpu single ownership linked lists (using local_t protection).
* Lockless linked lists.
* Allow RCU protected BPF allocated objects. This then allows RCU
protected list lookups, since spinlock protection for readers does
not scale.
* Introduce bpf_refcount for local kptrs, shared ownership.
* Introduce shared ownership linked lists.
* Documentation.
Changelog:
----------
v9 -> v10
v9: https://lore.kernel.org/bpf/
20221117225510.1676785-1-memxor@gmail.com
* Deduplicate code to find btf_record of reg (Alexei)
* Add linked_list test to DENYLIST.aarch64 (Alexei)
* Disable some linked list tests for now so that they compile with
clang nightly (Alexei)
v8 -> v9
v8: https://lore.kernel.org/bpf/
20221117162430.1213770-1-memxor@gmail.com
* Fix up commit log of patch 2, Simplify patch 3
* Explain the implicit requirement of bpf_list_head requiring map BTF
to match in btf_record_equal in a separate patch.
v7 -> v8
v7: https://lore.kernel.org/bpf/
20221114191547.1694267-1-memxor@gmail.com
* Fix early return in map_check_btf (Dan Carpenter)
* Fix two memory leak bugs in local storage maps, outer maps
* Address comments from Alexei and Dave
* More local kptr -> allocated object renaming
* Use krealloc with NULL instead kmalloc + krealloc
* Drop WARN_ON_ONCE for field_offs parsing
* Combine kfunc add + remove patches into one
* Drop STRONG suffix from KF_ARG_PTR_TO_KPTR
* Rename is_kfunc_arg_ret_buf_size to is_kfunc_arg_scalar_with_name
* Remove redundant check for reg->type and arg type in it
* Drop void * ret type check
* Remove code duplication in checks for NULL pointer with offset != 0
* Fix two bpf_list_node typos
* Improve log message for bpf_list_head operations
* Improve comments for active_lock struct
* Improve comments for Implementation details of process_spin_lock
* Add Dave's acks
v6 -> v7
v6: https://lore.kernel.org/bpf/
20221111193224.876706-1-memxor@gmail.com
* Fix uninitialized variable warning (Dan Carpenter, Kernel Test Robot)
* One more local_kptr renaming
v5 -> v6
v5: https://lore.kernel.org/bpf/
20221107230950.7117-1-memxor@gmail.com
* Replace (i && !off) check with next_off, include test (Andrii)
* Drop local kptrs naming (Andrii, Alexei)
* Drop reg->precise == EXACT patch (Andrii)
* Add comment about ptr member of struct active_lock (Andrii)
* Use btf__new_empty + btf__add_xxx APIs (Andrii)
* Address other misc nits from Andrii
v4 -> v5
v4: https://lore.kernel.org/bpf/
20221103191013.1236066-1-memxor@gmail.com
* Add a lot more selftests (failure, success, runtime, BTF)
* Make sure series is bisect friendly
* Move list draining out of spin lock
* This exposed an issue where bpf_mem_free can now be called in
map_free path without migrate_disable, also fixed that.
* Rename MEM_ALLOC -> MEM_RINGBUF, MEM_TYPE_LOCAL -> MEM_ALLOC (Alexei)
* Group lock identity into a struct active_lock { ptr, id } (Dave)
* Split set_release_on_unlock logic into separate patch (Alexei)
v3 -> v4
v3: https://lore.kernel.org/bpf/
20221102202658.963008-1-memxor@gmail.com
* Fix compiler error for !CONFIG_BPF_SYSCALL (Kernel Test Robot)
* Fix error due to BUILD_BUG_ON on 32-bit platforms (Kernel Test Robot)
v2 -> v3
v2: https://lore.kernel.org/bpf/
20221013062303.896469-1-memxor@gmail.com
* Add ack from Dave for patch 5
* Rename btf_type_fields -> btf_record, btf_type_fields_off ->
btf_field_offs, rename functions similarly (Alexei)
* Remove 'kind' component from contains declaration tag (Alexei)
* Move bpf_list_head, bpf_list_node definitions to UAPI bpf.h (Alexei)
* Add note in commit log about modifying btf_struct_access API (Dave)
* Downgrade WARN_ON_ONCE to verbose(env, "...") and return -EFAULT (Dave)
* Add type_is_local_kptr wrapper to avoid noisy checks (Dave)
* Remove unused flags parameter from bpf_kptr_new (Alexei)
* Rename bpf_kptr_new -> bpf_obj_new, bpf_kptr_drop -> bpf_obj_drop (Alexei)
* Reword comment in ref_obj_id_set_release_on_unlock (Dave)
* Fix return type of ref_obj_id_set_release_on_unlock (Dave)
* Introduce is_bpf_list_api_kfunc to dedup checks (Dave)
* Disallow BPF_WRITE to untrusted local kptrs
* Add details about soundness of check_reg_allocation_locked logic
* List untrusted local kptrs for PROBE_MEM handling
v1 -> v2
v1: https://lore.kernel.org/bpf/
20221011012240.3149-1-memxor@gmail.com
* Rebase on bpf-next to resolve merge conflict in DENYLIST.s390x
* Fix a couple of mental lapses in bpf_list_head_free
RFC v1 -> v1
RFC v1: https://lore.kernel.org/bpf/
20220904204145.3089-1-memxor@gmail.com
* Mostly a complete rewrite of BTF parsing, refactor existing code (Kartikeya)
* Rebase kfunc rewrite for bpf-next, add support for more changes
* Cache type metadata in BTF to avoid recomputation inside verifier (Kartikeya)
* Remove __kernel tag, make things similar to map values, reserve bpf_ prefix
* bpf_kptr_new, bpf_kptr_drop
* Rename precision state enum values (Alexei)
* Drop explicit constructor/destructor support (Alexei)
* Rewrite code for constructing/destructing objects and offload to runtime
* Minimize duplication in bpf_map_value_off_desc handling (Alexei)
* Expose global memory allocator (Alexei)
* Address other nits from Alexei
* Split out local kptrs in maps, more kptrs in maps support into a follow up
Links:
------
* Dave's BPF RB-Tree RFC series
v1 (Discussion thread)
https://lore.kernel.org/bpf/
20220722183438.3319790-1-davemarchevsky@fb.com
v2 (With support for static locks)
https://lore.kernel.org/bpf/
20220830172759.4069786-1-davemarchevsky@fb.com
* BPF Linked Lists Discussion
https://lore.kernel.org/bpf/CAP01T74U30+yeBHEgmgzTJ-XYxZ0zj71kqCDJtTH9YQNfTK+Xw@mail.gmail.com
* BPF Memory Allocator from Alexei
https://lore.kernel.org/bpf/
20220902211058.60789-1-alexei.starovoitov@gmail.com
* BPF Memory Allocator UAPI Discussion
https://lore.kernel.org/bpf/
d3f76b27f4e55ec9e400ae8dcaecbb702a4932e8.camel@fb.com
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:14 +0000 (07:26 +0530)]
selftests/bpf: Temporarily disable linked list tests
The latest clang nightly as of writing crashes with the given test case
for BPF linked lists wherever global glock, ghead, glock2 are used,
hence comment out the parts that cause the crash, and prepare this commit
so that it can be reverted when the fix has been made. More context in [0].
[0]: https://lore.kernel.org/bpf/
d56223f9-483e-fbc1-4564-
44c0858a1e3e@meta.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-25-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:13 +0000 (07:26 +0530)]
selftests/bpf: Add BTF sanity tests
Preparing the metadata for bpf_list_head involves a complicated parsing
step and type resolution for the contained value. Ensure that corner
cases are tested against and invalid specifications in source are duly
rejected. Also include tests for incorrect ownership relationships in
the BTF.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-24-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:12 +0000 (07:26 +0530)]
selftests/bpf: Add BPF linked list API tests
Include various tests covering the success and failure cases. Also, run
the success cases at runtime to verify correctness of linked list
manipulation routines, in addition to ensuring successful verification.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-23-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:11 +0000 (07:26 +0530)]
selftests/bpf: Add failure test cases for spin lock pairing
First, ensure that whenever a bpf_spin_lock is present in an allocation,
the reg->id is preserved. This won't be true for global variables
however, since they have a single map value per map, hence the verifier
harcodes it to 0 (so that multiple pseudo ldimm64 insns can yield the
same lock object per map at a given offset).
Next, add test cases for all possible combinations (kptr, global, map
value, inner map value). Since we lifted restriction on locking in inner
maps, also add test cases for them. Currently, each lookup into an inner
map gets a fresh reg->id, so even if the reg->map_ptr is same, they will
be treated as separate allocations and the incorrect unlock pairing will
be rejected.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-22-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:10 +0000 (07:26 +0530)]
selftests/bpf: Update spinlock selftest
Make updates in preparation for adding more test cases to this selftest:
- Convert from CHECK_ to ASSERT macros.
- Use BPF skeleton
- Fix typo sping -> spin
- Rename spinlock.c -> spin_lock.c
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-21-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:09 +0000 (07:26 +0530)]
selftests/bpf: Add __contains macro to bpf_experimental.h
Add user facing __contains macro which provides a convenient wrapper
over the verbose kernel specific BTF declaration tag required to
annotate BPF list head structs in user types.
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-20-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:08 +0000 (07:26 +0530)]
bpf: Add comments for map BTF matching requirement for bpf_list_head
The old behavior of bpf_map_meta_equal was that it compared timer_off
to be equal (but not spin_lock_off, because that was not allowed), and
did memcmp of kptr_off_tab.
Now, we memcmp the btf_record of two bpf_map structs, which has all
fields.
We preserve backwards compat as we kzalloc the array, so if only spin
lock and timer exist in map, we only compare offset while the rest of
unused members in the btf_field struct are zeroed out.
In case of kptr, btf and everything else is of vmlinux or module, so as
long type is same it will match, since kernel btf, module, dtor pointer
will be same across maps.
Now with list_head in the mix, things are a bit complicated. We
implicitly add a requirement that both BTFs are same, because struct
btf_field_list_head has btf and value_rec members.
We obviously shouldn't force BTFs to be equal by default, as that breaks
backwards compatibility.
Currently it is only implicitly required due to list_head matching
struct btf and value_rec member. value_rec points back into a btf_record
stashed in the map BTF (btf member of btf_field_list_head). So that
pointer and btf member has to match exactly.
Document all these subtle details so that things don't break in the
future when touching this code.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-19-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:07 +0000 (07:26 +0530)]
bpf: Add 'release on unlock' logic for bpf_list_push_{front,back}
This commit implements the delayed release logic for bpf_list_push_front
and bpf_list_push_back.
Once a node has been added to the list, it's pointer changes to
PTR_UNTRUSTED. However, it is only released once the lock protecting the
list is unlocked. For such PTR_TO_BTF_ID | MEM_ALLOC with PTR_UNTRUSTED
set but an active ref_obj_id, it is still permitted to read them as long
as the lock is held. Writing to them is not allowed.
This allows having read access to push items we no longer own until we
release the lock guarding the list, allowing a little more flexibility
when working with these APIs.
Note that enabling write support has fairly tricky interactions with
what happens inside the critical section. Just as an example, currently,
bpf_obj_drop is not permitted, but if it were, being able to write to
the PTR_UNTRUSTED pointer while the object gets released back to the
memory allocator would violate safety properties we wish to guarantee
(i.e. not crashing the kernel). The memory could be reused for a
different type in the BPF program or even in the kernel as it gets
eventually kfree'd.
Not enabling bpf_obj_drop inside the critical section would appear to
prevent all of the above, but that is more of an artifical limitation
right now. Since the write support is tangled with how we handle
potential aliasing of nodes inside the critical section that may or may
not be part of the list anymore, it has been deferred to a future patch.
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-18-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:06 +0000 (07:26 +0530)]
bpf: Introduce single ownership BPF linked list API
Add a linked list API for use in BPF programs, where it expects
protection from the bpf_spin_lock in the same allocation as the
bpf_list_head. For now, only one bpf_spin_lock can be present hence that
is assumed to be the one protecting the bpf_list_head.
The following functions are added to kick things off:
// Add node to beginning of list
void bpf_list_push_front(struct bpf_list_head *head, struct bpf_list_node *node);
// Add node to end of list
void bpf_list_push_back(struct bpf_list_head *head, struct bpf_list_node *node);
// Remove node at beginning of list and return it
struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head);
// Remove node at end of list and return it
struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head);
The lock protecting the bpf_list_head needs to be taken for all
operations. The verifier ensures that the lock that needs to be taken is
always held, and only the correct lock is taken for these operations.
These checks are made statically by relying on the reg->id preserved for
registers pointing into regions having both bpf_spin_lock and the
objects protected by it. The comment over check_reg_allocation_locked in
this change describes the logic in detail.
Note that bpf_list_push_front and bpf_list_push_back are meant to
consume the object containing the node in the 1st argument, however that
specific mechanism is intended to not release the ref_obj_id directly
until the bpf_spin_unlock is called. In this commit, nothing is done,
but the next commit will be introducing logic to handle this case, so it
has been left as is for now.
bpf_list_pop_front and bpf_list_pop_back delete the first or last item
of the list respectively, and return pointer to the element at the
list_node offset. The user can then use container_of style macro to get
the actual entry type. The verifier however statically knows the actual
type, so the safety properties are still preserved.
With these additions, programs can now manage their own linked lists and
store their objects in them.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-17-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:05 +0000 (07:26 +0530)]
bpf: Permit NULL checking pointer with non-zero fixed offset
Pointer increment on seeing PTR_MAYBE_NULL is already protected against,
hence make an exception for PTR_TO_BTF_ID | MEM_ALLOC while still
keeping the warning for other unintended cases that might creep in.
bpf_list_pop_{front,_back} helpers planned to be introduced in next
commit will return a MEM_ALLOC register with incremented offset pointing
to bpf_list_node field. The user is supposed to then obtain the pointer
to the entry using container_of after NULL checking it. The current
restrictions trigger a warning when doing the NULL checking. Revisiting
the reason, it is meant as an assertion which seems to actually work and
catch the bad case.
Hence, under no other circumstances can reg->off be non-zero for a
register that has the PTR_MAYBE_NULL type flag set.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-16-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:04 +0000 (07:26 +0530)]
bpf: Introduce bpf_obj_drop
Introduce bpf_obj_drop, which is the kfunc used to free allocated
objects (allocated using bpf_obj_new). Pairing with bpf_obj_new, it
implicitly destructs the fields part of object automatically without
user intervention.
Just like the previous patch, btf_struct_meta that is needed to free up
the special fields is passed as a hidden argument to the kfunc.
For the user, a convenience macro hides over the kernel side kfunc which
is named bpf_obj_drop_impl.
Continuing the previous example:
void prog(void) {
struct foo *f;
f = bpf_obj_new(typeof(*f));
if (!f)
return;
bpf_obj_drop(f);
}
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-15-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:03 +0000 (07:26 +0530)]
bpf: Introduce bpf_obj_new
Introduce type safe memory allocator bpf_obj_new for BPF programs. The
kernel side kfunc is named bpf_obj_new_impl, as passing hidden arguments
to kfuncs still requires having them in prototype, unlike BPF helpers
which always take 5 arguments and have them checked using bpf_func_proto
in verifier, ignoring unset argument types.
Introduce __ign suffix to ignore a specific kfunc argument during type
checks, then use this to introduce support for passing type metadata to
the bpf_obj_new_impl kfunc.
The user passes BTF ID of the type it wants to allocates in program BTF,
the verifier then rewrites the first argument as the size of this type,
after performing some sanity checks (to ensure it exists and it is a
struct type).
The second argument is also fixed up and passed by the verifier. This is
the btf_struct_meta for the type being allocated. It would be needed
mostly for the offset array which is required for zero initializing
special fields while leaving the rest of storage in unitialized state.
It would also be needed in the next patch to perform proper destruction
of the object's special fields.
Under the hood, bpf_obj_new will call bpf_mem_alloc and bpf_mem_free,
using the any context BPF memory allocator introduced recently. To this
end, a global instance of the BPF memory allocator is initialized on
boot to be used for this purpose. This 'bpf_global_ma' serves all
allocations for bpf_obj_new. In the future, bpf_obj_new variants will
allow specifying a custom allocator.
Note that now that bpf_obj_new can be used to allocate objects that can
be linked to BPF linked list (when future linked list helpers are
available), we need to also free the elements using bpf_mem_free.
However, since the draining of elements is done outside the
bpf_spin_lock, we need to do migrate_disable around the call since
bpf_list_head_free can be called from map free path where migration is
enabled. Otherwise, when called from BPF programs migration is already
disabled.
A convenience macro is included in the bpf_experimental.h header to hide
over the ugly details of the implementation, leading to user code
looking similar to a language level extension which allocates and
constructs fields of a user type.
struct bar {
struct bpf_list_node node;
};
struct foo {
struct bpf_spin_lock lock;
struct bpf_list_head head __contains(bar, node);
};
void prog(void) {
struct foo *f;
f = bpf_obj_new(typeof(*f));
if (!f)
return;
...
}
A key piece of this story is still missing, i.e. the free function,
which will come in the next patch.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-14-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:02 +0000 (07:26 +0530)]
bpf: Support constant scalar arguments for kfuncs
Allow passing known constant scalars as arguments to kfuncs that do not
represent a size parameter. We use mark_chain_precision for the constant
scalar argument to mark it precise. This makes the search pruning
optimization of verifier more conservative for such kfunc calls, and
each non-distinct argument is considered unequivalent.
We will use this support to then expose a bpf_obj_new function where it
takes the local type ID of a type in program BTF, and returns a
PTR_TO_BTF_ID | MEM_ALLOC to the local type, and allows programs to
allocate their own objects.
Each type ID resolves to a distinct type with a possibly distinct size,
hence the type ID constant matters in terms of program safety and its
precision needs to be checked between old and cur states inside regsafe.
The use of mark_chain_precision enables this.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-13-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:01 +0000 (07:26 +0530)]
bpf: Rewrite kfunc argument handling
As we continue to add more features, argument types, kfunc flags, and
different extensions to kfuncs, the code to verify the correctness of
the kfunc prototype wrt the passed in registers has become ad-hoc and
ugly to read. To make life easier, and make a very clear split between
different stages of argument processing, move all the code into
verifier.c and refactor into easier to read helpers and functions.
This also makes sharing code within the verifier easier with kfunc
argument processing. This will be more and more useful in later patches
as we are now moving to implement very core BPF helpers as kfuncs, to
keep them experimental before baking into UAPI.
Remove all kfunc related bits now from btf_check_func_arg_match, as
users have been converted away to refactored kfunc argument handling.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-12-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:56:00 +0000 (07:26 +0530)]
bpf: Allow locking bpf_spin_lock in inner map values
There is no need to restrict users from locking bpf_spin_lock in map
values of inner maps. Each inner map lookup gets a unique reg->id
assigned to the returned PTR_TO_MAP_VALUE which will be preserved after
the NULL check. Distinct lookups into different inner map get unique
IDs, and distinct lookups into same inner map also get unique IDs.
Hence, lift the restriction by removing the check return -ENOTSUPP in
map_in_map.c. Later commits will add comprehensive test cases to ensure
that invalid cases are rejected.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-11-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:55:59 +0000 (07:25 +0530)]
bpf: Allow locking bpf_spin_lock global variables
Global variables reside in maps accessible using direct_value_addr
callbacks, so giving each load instruction's rewrite a unique reg->id
disallows us from holding locks which are global.
The reason for preserving reg->id as a unique value for registers that
may point to spin lock is that two separate lookups are treated as two
separate memory regions, and any possible aliasing is ignored for the
purposes of spin lock correctness.
This is not great especially for the global variable case, which are
served from maps that have max_entries == 1, i.e. they always lead to
map values pointing into the same map value.
So refactor the active_spin_lock into a 'active_lock' structure which
represents the lock identity, and instead of the reg->id, remember two
fields, a pointer and the reg->id. The pointer will store reg->map_ptr
or reg->btf. It's only necessary to distinguish for the id == 0 case of
global variables, but always setting the pointer to a non-NULL value and
using the pointer to check whether the lock is held simplifies code in
the verifier.
This is generic enough to allow it for global variables, map lookups,
and allocated objects at the same time.
Note that while whether a lock is held can be answered by just comparing
active_lock.ptr to NULL, to determine whether the register is pointing
to the same held lock requires comparing _both_ ptr and id.
Finally, as a result of this refactoring, pseudo load instructions are
not given a unique reg->id, as they are doing lookup for the same map
value (max_entries is never greater than 1).
Essentially, we consider that the tuple of (ptr, id) will always be
unique for any kind of argument to bpf_spin_{lock,unlock}.
Note that this can be extended in the future to also remember offset
used for locking, so that we can introduce multiple bpf_spin_lock fields
in the same allocation.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-10-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:55:58 +0000 (07:25 +0530)]
bpf: Allow locking bpf_spin_lock in allocated objects
Allow locking a bpf_spin_lock in an allocated object, in addition to
already supported map value pointers. The handling is similar to that of
map values, by just preserving the reg->id of PTR_TO_BTF_ID | MEM_ALLOC
as well, and adjusting process_spin_lock to work with them and remember
the id in verifier state.
Refactor the existing process_spin_lock to work with PTR_TO_BTF_ID |
MEM_ALLOC in addition to PTR_TO_MAP_VALUE. We need to update the
reg_may_point_to_spin_lock which is used in mark_ptr_or_null_reg to
preserve reg->id, that will be used in env->cur_state->active_spin_lock
to remember the currently held spin lock.
Also update the comment describing bpf_spin_lock implementation details
to also talk about PTR_TO_BTF_ID | MEM_ALLOC type.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-9-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:55:57 +0000 (07:25 +0530)]
bpf: Verify ownership relationships for user BTF types
Ensure that there can be no ownership cycles among different types by
way of having owning objects that can hold some other type as their
element. For instance, a map value can only hold allocated objects, but
these are allowed to have another bpf_list_head. To prevent unbounded
recursion while freeing resources, elements of bpf_list_head in local
kptrs can never have a bpf_list_head which are part of list in a map
value. Later patches will verify this by having dedicated BTF selftests.
Also, to make runtime destruction easier, once btf_struct_metas is fully
populated, we can stash the metadata of the value type directly in the
metadata of the list_head fields, as that allows easier access to the
value type's layout to destruct it at runtime from the btf_field entry
of the list head itself.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-8-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:55:56 +0000 (07:25 +0530)]
bpf: Recognize lock and list fields in allocated objects
Allow specifying bpf_spin_lock, bpf_list_head, bpf_list_node fields in a
allocated object.
Also update btf_struct_access to reject direct access to these special
fields.
A bpf_list_head allows implementing map-in-map style use cases, where an
allocated object with bpf_list_head is linked into a list in a map
value. This would require embedding a bpf_list_node, support for which
is also included. The bpf_spin_lock is used to protect the bpf_list_head
and other data.
While we strictly don't require to hold a bpf_spin_lock while touching
the bpf_list_head in such objects, as when have access to it, we have
complete ownership of the object, the locking constraint is still kept
and may be conditionally lifted in the future.
Note that the specification of such types can be done just like map
values, e.g.:
struct bar {
struct bpf_list_node node;
};
struct foo {
struct bpf_spin_lock lock;
struct bpf_list_head head __contains(bar, node);
struct bpf_list_node node;
};
struct map_value {
struct bpf_spin_lock lock;
struct bpf_list_head head __contains(foo, node);
};
To recognize such types in user BTF, we build a btf_struct_metas array
of metadata items corresponding to each BTF ID. This is done once during
the btf_parse stage to avoid having to do it each time during the
verification process's requirement to inspect the metadata.
Moreover, the computed metadata needs to be passed to some helpers in
future patches which requires allocating them and storing them in the
BTF that is pinned by the program itself, so that valid access can be
assumed to such data during program runtime.
A key thing to note is that once a btf_struct_meta is available for a
type, both the btf_record and btf_field_offs should be available. It is
critical that btf_field_offs is available in case special fields are
present, as we extensively rely on special fields being zeroed out in
map values and allocated objects in later patches. The code ensures that
by bailing out in case of errors and ensuring both are available
together. If the record is not available, the special fields won't be
recognized, so not having both is also fine (in terms of being a
verification error and not a runtime bug).
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:55:55 +0000 (07:25 +0530)]
bpf: Introduce allocated objects support
Introduce support for representing pointers to objects allocated by the
BPF program, i.e. PTR_TO_BTF_ID that point to a type in program BTF.
This is indicated by the presence of MEM_ALLOC type flag in reg->type to
avoid having to check btf_is_kernel when trying to match argument types
in helpers.
Whenever walking such types, any pointers being walked will always yield
a SCALAR instead of pointer. In the future we might permit kptr inside
such allocated objects (either kernel or program allocated), and it will
then form a PTR_TO_BTF_ID of the respective type.
For now, such allocated objects will always be referenced in verifier
context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
to such objects, as long fields that are special are not touched
(support for which will be added in subsequent patches). Note that once
such a pointer is marked PTR_UNTRUSTED, it is no longer allowed to write
to it.
No PROBE_MEM handling is therefore done for loads into this type unless
PTR_UNTRUSTED is part of the register type, since they can never be in
an undefined state, and their lifetime will always be valid.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-6-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:55:54 +0000 (07:25 +0530)]
bpf: Populate field_offs for inner_map_meta
Far too much code simply assumes that both btf_record and btf_field_offs
are set to valid pointers together, or both are unset. They go together
hand in hand as btf_record describes the special fields and
btf_field_offs is compact representation for runtime copying/zeroing.
It is very difficult to make this clear in the code when the only
exception to this universal invariant is inner_map_meta which is used
as reg->map_ptr in the verifier. This is simply a bug waiting to happen,
as in verifier context we cannot easily distinguish if PTR_TO_MAP_VALUE
is coming from an inner map, and if we ever end up using field_offs for
any reason in the future, we will silently ignore the special fields for
inner map case (as NULL is not an error but unset field_offs).
Hence, simply copy field_offs from inner map together with btf_record.
While at it, refactor code to unwind properly on errors with gotos.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:55:53 +0000 (07:25 +0530)]
bpf: Free inner_map_meta when btf_record_dup fails
Whenever btf_record_dup fails, we must free inner_map_meta that was
allocated before.
This fixes a memory leak (in case of errors) during inner map creation.
Fixes:
aa3496accc41 ("bpf: Refactor kptr_off_tab into btf_record")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:55:52 +0000 (07:25 +0530)]
bpf: Do btf_record_free outside map_free callback
Since the commit being fixed, we now miss freeing btf_record for local
storage maps which will have a btf_record populated in case they have
bpf_spin_lock element.
This was missed because I made the choice of offloading the job to free
kptr_off_tab (now btf_record) to the map_free callback when adding
support for kptrs.
Revisiting the reason for this decision, there is the possibility that
the btf_record gets used inside map_free callback (e.g. in case of maps
embedding kptrs) to iterate over them and free them, hence doing it
before the map_free callback would be leaking special field memory, and
do invalid memory access. The btf_record keeps module references which
is critical to ensure the dtor call made for referenced kptr is safe to
do.
If doing it after map_free callback, the map area is already freed, so
we cannot access bpf_map structure anymore.
To fix this and prevent such lapses in future, move bpf_map_free_record
out of the map_free callback, and do it after map_free by remembering
the btf_record pointer. There is no need to access bpf_map structure in
that case, and we can avoid missing this case when support for new map
types is added for other special fields.
Since a btf_record and its btf_field_offs are used together, for
consistency delay freeing of field_offs as well. While not a problem
right now, a lot of code assumes that either both record and field_offs
are set or none at once.
Note that in case of map of maps (outer maps), inner_map_meta->record is
only used during verification, not to free fields in map value, hence we
simply keep the bpf_map_free_record call as is in bpf_map_meta_free and
never touch map->inner_map_meta in bpf_map_free_deferred.
Add a comment making note of these details.
Fixes:
db559117828d ("bpf: Consolidate spin_lock, timer management into btf_record")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-3-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Fri, 18 Nov 2022 01:55:51 +0000 (07:25 +0530)]
bpf: Fix early return in map_check_btf
Instead of returning directly with -EOPNOTSUPP for the timer case, we
need to free the btf_record before returning to userspace.
Fixes:
db559117828d ("bpf: Consolidate spin_lock, timer management into btf_record")
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221118015614.2013203-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Björn Töpel [Tue, 15 Nov 2022 18:20:51 +0000 (19:20 +0100)]
selftests/bpf: Pass target triple to get_sys_includes macro
When cross-compiling [1], the get_sys_includes make macro should use
the target system include path, and not the build hosts system include
path.
Make clang honor the CROSS_COMPILE triple.
[1] e.g. "ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- make"
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Link: https://lore.kernel.org/bpf/20221115182051.582962-2-bjorn@kernel.org
Björn Töpel [Tue, 15 Nov 2022 18:20:50 +0000 (19:20 +0100)]
selftests/bpf: Explicitly pass RESOLVE_BTFIDS to sub-make
When cross-compiling selftests/bpf, the resolve_btfids binary end up
in a different directory, than the regular resolve_btfids
builds. Populate RESOLVE_BTFIDS for sub-make, so it can find the
binary.
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20221115182051.582962-1-bjorn@kernel.org
Hou Tao [Wed, 16 Nov 2022 07:50:58 +0000 (15:50 +0800)]
bpf: Pass map file to .map_update_batch directly
Currently bpf_map_do_batch() first invokes fdget(batch.map_fd) to get
the target map file, then it invokes generic_map_update_batch() to do
batch update. generic_map_update_batch() will get the target map file
by using fdget(batch.map_fd) again and pass it to bpf_map_update_value().
The problem is map file returned by the second fdget() may be NULL or a
totally different file compared by map file in bpf_map_do_batch(). The
reason is that the first fdget() only guarantees the liveness of struct
file instead of file descriptor and the file description may be released
by concurrent close() through pick_file().
It doesn't incur any problem as for now, because maps with batch update
support don't use map file in .map_fd_get_ptr() ops. But it is better to
fix the potential access of an invalid map file.
Using __bpf_map_get() again in generic_map_update_batch() can not fix
the problem, because batch.map_fd may be closed and reopened, and the
returned map file may be different with map file got in
bpf_map_do_batch(), so just passing the map file directly to
.map_update_batch() in bpf_map_do_batch().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221116075059.1551277-1-houtao@huaweicloud.com
Daniel Müller [Wed, 16 Nov 2022 17:43:58 +0000 (17:43 +0000)]
bpf/docs: Include blank lines between bullet points in bpf_devel_QA.rst
Commit
26a9b433cf08 ("bpf/docs: Document how to run CI without patch
submission") caused a warning to be generated when compiling the
documentation:
> bpf_devel_QA.rst:55: WARNING: Unexpected indentation.
> bpf_devel_QA.rst:56: WARNING: Block quote ends without a blank line
This change fixes the problem by inserting the required blank lines.
Fixes:
26a9b433cf08 ("bpf/docs: Document how to run CI without patch submission")
Reported-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Daniel Müller <deso@posteo.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Akira Yokosawa <akiyks@gmail.com>
Link: https://lore.kernel.org/bpf/20221116174358.2744613-1-deso@posteo.net
Wang Yufen [Tue, 15 Nov 2022 03:29:40 +0000 (11:29 +0800)]
selftests/bpf: fix memory leak of lsm_cgroup
kmemleak reports this issue:
unreferenced object 0xffff88810b7835c0 (size 32):
comm "test_progs", pid 270, jiffies
4294969007 (age 1621.315s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
03 00 00 00 03 00 00 00 0f 00 00 00 00 00 00 00 ................
backtrace:
[<
00000000376cdeab>] kmalloc_trace+0x27/0x110
[<
000000003bcdb3b6>] selinux_sk_alloc_security+0x66/0x110
[<
000000003959008f>] security_sk_alloc+0x47/0x80
[<
00000000e7bc6668>] sk_prot_alloc+0xbd/0x1a0
[<
0000000002d6343a>] sk_alloc+0x3b/0x940
[<
000000009812a46d>] unix_create1+0x8f/0x3d0
[<
000000005ed0976b>] unix_create+0xa1/0x150
[<
0000000086a1d27f>] __sock_create+0x233/0x4a0
[<
00000000cffe3a73>] __sys_socket_create.part.0+0xaa/0x110
[<
0000000007c63f20>] __sys_socket+0x49/0xf0
[<
00000000b08753c8>] __x64_sys_socket+0x42/0x50
[<
00000000b56e26b3>] do_syscall_64+0x3b/0x90
[<
000000009b4871b8>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
The issue occurs in the following scenarios:
unix_create1()
sk_alloc()
sk_prot_alloc()
security_sk_alloc()
call_int_hook()
hlist_for_each_entry()
entry1->hook.sk_alloc_security
<-- selinux_sk_alloc_security() succeeded,
<-- sk->security alloced here.
entry2->hook.sk_alloc_security
<-- bpf_lsm_sk_alloc_security() failed
goto out_free;
... <-- the sk->security not freed, memleak
The core problem is that the LSM is not yet fully stacked (work is
actively going on in this space) which means that some LSM hooks do
not support multiple LSMs at the same time. To fix, skip the
"EPERM" test when it runs in the environments that already have
non-bpf lsms installed
Fixes:
dca85aac8895 ("selftests/bpf: lsm_cgroup functional test")
Signed-off-by: Wang Yufen <wangyufen@huawei.com>
Cc: Stanislav Fomichev <sdf@google.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/1668482980-16163-1-git-send-email-wangyufen@huawei.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Eduard Zingerman [Wed, 16 Nov 2022 01:54:56 +0000 (03:54 +0200)]
selftests/bpf: allow unpriv bpf for selftests by default
Enable unprivileged bpf for selftests kernel by default.
This forces CI to run test_verifier tests in both privileged
and unprivileged modes.
The test_verifier.c:do_test uses sysctl kernel.unprivileged_bpf_disabled
to decide whether to run or to skip test cases in unprivileged mode.
The CONFIG_BPF_UNPRIV_DEFAULT_OFF controls the default value of the
kernel.unprivileged_bpf_disabled.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20221116015456.2461135-1-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tiezhu Yang [Tue, 15 Nov 2022 13:00:07 +0000 (21:00 +0800)]
bpftool: Check argc first before "file" in do_batch()
If the parameters for batch are more than 2, check argc first can
return immediately, no need to use is_prefix() to check "file" with
a little overhead and then check argc, it is better to check "file"
only when the parameters for batch are 2.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Acked-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/1668517207-11822-1-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Donald Hunter [Tue, 15 Nov 2022 09:59:10 +0000 (09:59 +0000)]
docs/bpf: Fix sample code in MAP_TYPE_ARRAY docs
Remove mistaken & from code example in MAP_TYPE_ARRAY docs
Fixes:
1cfa97b30c5a ("bpf, docs: Document BPF_MAP_TYPE_ARRAY")
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://lore.kernel.org/r/20221115095910.86407-1-donald.hunter@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Alexei Starovoitov [Wed, 16 Nov 2022 01:38:36 +0000 (17:38 -0800)]
Merge branch 'propagate nullness information for reg to reg comparisons'
Eduard Zingerman says:
====================
This patchset adds ability to propagates nullness information for
branches of register to register equality compare instructions. The
following rules are used:
- suppose register A maybe null
- suppose register B is not null
- for JNE A, B, ... - A is not null in the false branch
- for JEQ A, B, ... - A is not null in the true branch
E.g. for program like below:
r6 = skb->sk;
r7 = sk_fullsock(r6);
r0 = sk_fullsock(r6);
if (r0 == 0) return 0; (a)
if (r0 != r7) return 0; (b)
*r7->type; (c)
return 0;
It is safe to dereference r7 at point (c), because of (a) and (b).
The utility of this change came up while working on BPF CLang backend
issue [1]. Specifically, while debugging issue with selftest
`test_sk_lookup.c`. This test has the following structure:
int access_ctx_sk(struct bpf_sk_lookup *ctx __CTX__)
{
struct bpf_sock *sk1 = NULL, *sk2 = NULL;
...
sk1 = bpf_map_lookup_elem(&redir_map, &KEY_SERVER_A);
if (!sk1) // (a)
goto out;
...
if (ctx->sk != sk1) // (b)
goto out;
...
if (ctx->sk->family != AF_INET || // (c)
ctx->sk->type != SOCK_STREAM ||
ctx->sk->state != BPF_TCP_LISTEN)
goto out;
...
}
- at (a) `sk1` is checked to be not null;
- at (b) `ctx->sk` is verified to be equal to `sk1`;
- at (c) `ctx->sk` is accessed w/o nullness check.
Currently Global Value Numbering pass considers expressions `sk1` and
`ctx->sk` to be identical at point (c) and replaces `ctx->sk` with
`sk1` (not expressions themselves but corresponding SSA values).
Since `sk1` is known to be not null after (b) verifier allows
execution of the program.
However, such optimization is not guaranteed to happen. When it does
not happen verifier reports an error.
Changelog:
v2 -> v3:
- verifier tests are updated with correct error message for
unprivileged mode (pointer comparisons are forbidden in
unprivileged mode).
v1 -> v2:
- after investigation described in [2] as suggested by John, Daniel
and Shung-Hsi, function `type_is_pointer` is removed, calls to this
function are replaced by `__is_pointer_value(false, src_reg)`.
RFC -> v1:
- newly added if block in `check_cond_jmp_op` is moved down to keep
`make_ptr_not_null_reg` actions together;
- tests rewritten to have a single `r0 = 0; exit;` block.
[1] https://reviews.llvm.org/D131633#3722231
[2] https://lore.kernel.org/bpf/
bad8be826d088e0d180232628160bf932006de89.camel@gmail.com/
[RFC] https://lore.kernel.org/bpf/
20220822094312.175448-1-eddyz87@gmail.com/
[v1] https://lore.kernel.org/bpf/
20220826172915.1536914-1-eddyz87@gmail.com/
[v2] https://lore.kernel.org/bpf/
20221106214921.117631-1-eddyz87@gmail.com/
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Eduard Zingerman [Tue, 15 Nov 2022 22:48:59 +0000 (00:48 +0200)]
selftests/bpf: check nullness propagation for reg to reg comparisons
Verify that nullness information is porpagated in the branches of
register to register JEQ and JNE operations.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221115224859.2452988-3-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Eduard Zingerman [Tue, 15 Nov 2022 22:48:58 +0000 (00:48 +0200)]
bpf: propagate nullness information for reg to reg comparisons
Propagate nullness information for branches of register to register
equality compare instructions. The following rules are used:
- suppose register A maybe null
- suppose register B is not null
- for JNE A, B, ... - A is not null in the false branch
- for JEQ A, B, ... - A is not null in the true branch
E.g. for program like below:
r6 = skb->sk;
r7 = sk_fullsock(r6);
r0 = sk_fullsock(r6);
if (r0 == 0) return 0; (a)
if (r0 != r7) return 0; (b)
*r7->type; (c)
return 0;
It is safe to dereference r7 at point (c), because of (a) and (b).
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221115224859.2452988-2-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Toke Høiland-Jørgensen [Tue, 8 Nov 2022 14:06:00 +0000 (15:06 +0100)]
bpf: Expand map key argument of bpf_redirect_map to u64
For queueing packets in XDP we want to add a new redirect map type with
support for 64-bit indexes. To prepare fore this, expand the width of the
'key' argument to the bpf_redirect_map() helper. Since BPF registers are
always 64-bit, this should be safe to do after the fact.
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20221108140601.149971-3-toke@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Toke Høiland-Jørgensen [Tue, 8 Nov 2022 14:05:59 +0000 (15:05 +0100)]
dev: Move received_rps counter next to RPS members in softnet data
Move the received_rps counter value next to the other RPS-related members
in softnet_data. This closes two four-byte holes in the structure, making
room for another pointer in the first two cache lines without bumping the
xmit struct to its own line.
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20221108140601.149971-2-toke@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Daniel Müller [Mon, 14 Nov 2022 21:15:01 +0000 (21:15 +0000)]
bpf/docs: Document how to run CI without patch submission
This change documents the process for running the BPF CI before
submitting a patch to the upstream mailing list, similar to what happens
if a patch is send to bpf@vger.kernel.org: it builds kernel and
selftests and runs the latter on different architecture (but it notably
does not cover stylistic checks such as cover letter verification).
Running BPF CI this way can help achieve better test coverage ahead of
patch submission than merely running locally (say, using
tools/testing/selftests/bpf/vmtest.sh), as additional architectures may
be covered as well.
Signed-off-by: Daniel Müller <deso@posteo.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221114211501.2068684-1-deso@posteo.net
Kumar Kartikeya Dwivedi [Mon, 14 Nov 2022 19:15:28 +0000 (00:45 +0530)]
bpf: Refactor btf_struct_access
Instead of having to pass multiple arguments that describe the register,
pass the bpf_reg_state into the btf_struct_access callback. Currently,
all call sites simply reuse the btf and btf_id of the reg they want to
check the access of. The only exception to this pattern is the callsite
in check_ptr_to_map_access, hence for that case create a dummy reg to
simulate PTR_TO_BTF_ID access.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221114191547.1694267-8-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Mon, 14 Nov 2022 19:15:27 +0000 (00:45 +0530)]
bpf: Rename MEM_ALLOC to MEM_RINGBUF
Currently, verifier uses MEM_ALLOC type tag to specially tag memory
returned from bpf_ringbuf_reserve helper. However, this is currently
only used for this purpose and there is an implicit assumption that it
only refers to ringbuf memory (e.g. the check for ARG_PTR_TO_ALLOC_MEM
in check_func_arg_reg_off).
Hence, rename MEM_ALLOC to MEM_RINGBUF to indicate this special
relationship and instead open the use of MEM_ALLOC for more generic
allocations made for user types.
Also, since ARG_PTR_TO_ALLOC_MEM_OR_NULL is unused, simply drop it.
Finally, update selftests using 'alloc_' verifier string to 'ringbuf_'.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221114191547.1694267-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Mon, 14 Nov 2022 19:15:26 +0000 (00:45 +0530)]
bpf: Rename RET_PTR_TO_ALLOC_MEM
Currently, the verifier has two return types, RET_PTR_TO_ALLOC_MEM, and
RET_PTR_TO_ALLOC_MEM_OR_NULL, however the former is confusingly named to
imply that it carries MEM_ALLOC, while only the latter does. This causes
confusion during code review leading to conclusions like that the return
value of RET_PTR_TO_DYNPTR_MEM_OR_NULL (which is RET_PTR_TO_ALLOC_MEM |
PTR_MAYBE_NULL) may be consumable by bpf_ringbuf_{submit,commit}.
Rename it to make it clear MEM_ALLOC needs to be tacked on top of
RET_PTR_TO_MEM.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221114191547.1694267-6-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kumar Kartikeya Dwivedi [Mon, 14 Nov 2022 19:15:25 +0000 (00:45 +0530)]
bpf: Support bpf_list_head in map values
Add the support on the map side to parse, recognize, verify, and build
metadata table for a new special field of the type struct bpf_list_head.
To parameterize the bpf_list_head for a certain value type and the
list_node member it will accept in that value type, we use BTF
declaration tags.
The definition of bpf_list_head in a map value will be done as follows:
struct foo {
struct bpf_list_node node;
int data;
};
struct map_value {
struct bpf_list_head head __contains(foo, node);
};
Then, the bpf_list_head only allows adding to the list 'head' using the
bpf_list_node 'node' for the type struct foo.
The 'contains' annotation is a BTF declaration tag composed of four
parts, "contains:name:node" where the name is then used to look up the
type in the map BTF, with its kind hardcoded to BTF_KIND_STRUCT during
the lookup. The node defines name of the member in this type that has
the type struct bpf_list_node, which is actually used for linking into
the linked list. For now, 'kind' part is hardcoded as struct.
This allows building intrusive linked lists in BPF, using container_of
to obtain pointer to entry, while being completely type safe from the
perspective of the verifier. The verifier knows exactly the type of the
nodes, and knows that list helpers return that type at some fixed offset
where the bpf_list_node member used for this list exists. The verifier
also uses this information to disallow adding types that are not
accepted by a certain list.
For now, no elements can be added to such lists. Support for that is
coming in future patches, hence draining and freeing items is done with
a TODO that will be resolved in a future patch.
Note that the bpf_list_head_free function moves the list out to a local
variable under the lock and releases it, doing the actual draining of
the list items outside the lock. While this helps with not holding the
lock for too long pessimizing other concurrent list operations, it is
also necessary for deadlock prevention: unless every function called in
the critical section would be notrace, a fentry/fexit program could
attach and call bpf_map_update_elem again on the map, leading to the
same lock being acquired if the key matches and lead to a deadlock.
While this requires some special effort on part of the BPF programmer to
trigger and is highly unlikely to occur in practice, it is always better
if we can avoid such a condition.
While notrace would prevent this, doing the draining outside the lock
has advantages of its own, hence it is used to also fix the deadlock
related problem.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221114191547.1694267-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>