From 79a7f8bdb159d9914b58740f3d31d602a6e4aca8 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 13 May 2021 17:36:03 -0700 Subject: [PATCH] bpf: Introduce bpf_sys_bpf() helper and program type. Add placeholders for bpf_sys_bpf() helper and new program type. Make sure to check that expected_attach_type is zero for future extensibility. Allow tracing helper functions to be used in this program type, since they will only execute from user context via bpf_prog_test_run. Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Acked-by: John Fastabend Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210514003623.28033-2-alexei.starovoitov@gmail.com --- include/linux/bpf.h | 10 ++++++++ include/linux/bpf_types.h | 2 ++ include/uapi/linux/bpf.h | 8 +++++++ kernel/bpf/syscall.c | 53 ++++++++++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 8 +++++++ net/bpf/test_run.c | 43 ++++++++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 8 +++++++ 7 files changed, 132 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 02b02cb..04a2bf4 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1826,6 +1826,9 @@ static inline bool bpf_map_is_dev_bound(struct bpf_map *map) struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr); void bpf_map_offload_map_free(struct bpf_map *map); +int bpf_prog_test_run_syscall(struct bpf_prog *prog, + const union bpf_attr *kattr, + union bpf_attr __user *uattr); #else static inline int bpf_prog_offload_init(struct bpf_prog *prog, union bpf_attr *attr) @@ -1851,6 +1854,13 @@ static inline struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr) static inline void bpf_map_offload_map_free(struct bpf_map *map) { } + +static inline int bpf_prog_test_run_syscall(struct bpf_prog *prog, + const union bpf_attr *kattr, + union bpf_attr __user *uattr) +{ + return -ENOTSUPP; +} #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */ #if defined(CONFIG_INET) && defined(CONFIG_BPF_SYSCALL) diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h index f883f01..a9db1ea 100644 --- a/include/linux/bpf_types.h +++ b/include/linux/bpf_types.h @@ -77,6 +77,8 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_LSM, lsm, void *, void *) #endif /* CONFIG_BPF_LSM */ #endif +BPF_PROG_TYPE(BPF_PROG_TYPE_SYSCALL, bpf_syscall, + void *, void *) BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops) BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index ec6d85a..c92648f 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -937,6 +937,7 @@ enum bpf_prog_type { BPF_PROG_TYPE_EXT, BPF_PROG_TYPE_LSM, BPF_PROG_TYPE_SK_LOOKUP, + BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */ }; enum bpf_attach_type { @@ -4735,6 +4736,12 @@ union bpf_attr { * be zero-terminated except when **str_size** is 0. * * Or **-EBUSY** if the per-CPU memory copy buffer is busy. + * + * long bpf_sys_bpf(u32 cmd, void *attr, u32 attr_size) + * Description + * Execute bpf syscall with given arguments. + * Return + * A syscall result. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -4903,6 +4910,7 @@ union bpf_attr { FN(check_mtu), \ FN(for_each_map_elem), \ FN(snprintf), \ + FN(sys_bpf), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 941ca06d..b1e7352 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2014,6 +2014,7 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type, if (expected_attach_type == BPF_SK_LOOKUP) return 0; return -EINVAL; + case BPF_PROG_TYPE_SYSCALL: case BPF_PROG_TYPE_EXT: if (expected_attach_type) return -EINVAL; @@ -4508,3 +4509,55 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz return err; } + +static bool syscall_prog_is_valid_access(int off, int size, + enum bpf_access_type type, + const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + if (off < 0 || off >= U16_MAX) + return false; + if (off % size != 0) + return false; + return true; +} + +BPF_CALL_3(bpf_sys_bpf, int, cmd, void *, attr, u32, attr_size) +{ + return -EINVAL; +} + +const struct bpf_func_proto bpf_sys_bpf_proto = { + .func = bpf_sys_bpf, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_ANYTHING, + .arg2_type = ARG_PTR_TO_MEM, + .arg3_type = ARG_CONST_SIZE, +}; + +const struct bpf_func_proto * __weak +tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) +{ + return bpf_base_func_proto(func_id); +} + +static const struct bpf_func_proto * +syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) +{ + switch (func_id) { + case BPF_FUNC_sys_bpf: + return &bpf_sys_bpf_proto; + default: + return tracing_prog_func_proto(func_id, prog); + } +} + +const struct bpf_verifier_ops bpf_syscall_verifier_ops = { + .get_func_proto = syscall_prog_func_proto, + .is_valid_access = syscall_prog_is_valid_access, +}; + +const struct bpf_prog_ops bpf_syscall_prog_ops = { + .test_run = bpf_prog_test_run_syscall, +}; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index bdfdb54..37407d8 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -13196,6 +13196,14 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) int ret; u64 key; + if (prog->type == BPF_PROG_TYPE_SYSCALL) { + if (prog->aux->sleepable) + /* attach_btf_id checked to be zero already */ + return 0; + verbose(env, "Syscall programs can only be sleepable\n"); + return -EINVAL; + } + if (prog->aux->sleepable && prog->type != BPF_PROG_TYPE_TRACING && prog->type != BPF_PROG_TYPE_LSM) { verbose(env, "Only fentry/fexit/fmod_ret and lsm programs can be sleepable\n"); diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index a5d72c4..a6972d7 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -918,3 +918,46 @@ out: kfree(user_ctx); return ret; } + +int bpf_prog_test_run_syscall(struct bpf_prog *prog, + const union bpf_attr *kattr, + union bpf_attr __user *uattr) +{ + void __user *ctx_in = u64_to_user_ptr(kattr->test.ctx_in); + __u32 ctx_size_in = kattr->test.ctx_size_in; + void *ctx = NULL; + u32 retval; + int err = 0; + + /* doesn't support data_in/out, ctx_out, duration, or repeat or flags */ + if (kattr->test.data_in || kattr->test.data_out || + kattr->test.ctx_out || kattr->test.duration || + kattr->test.repeat || kattr->test.flags) + return -EINVAL; + + if (ctx_size_in < prog->aux->max_ctx_offset || + ctx_size_in > U16_MAX) + return -EINVAL; + + if (ctx_size_in) { + ctx = kzalloc(ctx_size_in, GFP_USER); + if (!ctx) + return -ENOMEM; + if (copy_from_user(ctx, ctx_in, ctx_size_in)) { + err = -EFAULT; + goto out; + } + } + retval = bpf_prog_run_pin_on_cpu(prog, ctx); + + if (copy_to_user(&uattr->test.retval, &retval, sizeof(u32))) { + err = -EFAULT; + goto out; + } + if (ctx_size_in) + if (copy_to_user(ctx_in, ctx, ctx_size_in)) + err = -EFAULT; +out: + kfree(ctx); + return err; +} diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index ec6d85a..c92648f 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -937,6 +937,7 @@ enum bpf_prog_type { BPF_PROG_TYPE_EXT, BPF_PROG_TYPE_LSM, BPF_PROG_TYPE_SK_LOOKUP, + BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */ }; enum bpf_attach_type { @@ -4735,6 +4736,12 @@ union bpf_attr { * be zero-terminated except when **str_size** is 0. * * Or **-EBUSY** if the per-CPU memory copy buffer is busy. + * + * long bpf_sys_bpf(u32 cmd, void *attr, u32 attr_size) + * Description + * Execute bpf syscall with given arguments. + * Return + * A syscall result. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -4903,6 +4910,7 @@ union bpf_attr { FN(check_mtu), \ FN(for_each_map_elem), \ FN(snprintf), \ + FN(sys_bpf), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper -- 2.7.4