bpf: netfilter: Add BPF_NETFILTER bpf_attach_type

Andrii Nakryiko writes:

 And we currently don't have an attach type for NETLINK BPF link.
 Thankfully it's not too late to add it. I see that link_create() in
 kernel/bpf/syscall.c just bypasses attach_type check. We shouldn't
 have done that. Instead we need to add BPF_NETLINK attach type to enum
 bpf_attach_type. And wire all that properly throughout the kernel and
 libbpf itself.

This adds BPF_NETFILTER and uses it.  This breaks uabi but this
wasn't in any non-rc release yet, so it should be fine.

v2: check link_attack prog type in link_create too

Fixes: 84601d6ee68a ("bpf: add bpf_link support for BPF_NETFILTER programs")
Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/CAEf4BzZ69YgrQW7DHCJUT_X+GqMq_ZQQPBwopaJJVGFD5=d5Vg@mail.gmail.com/
Link: https://lore.kernel.org/bpf/20230605131445.32016-1-fw@strlen.de

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 1bb11a6ee6676b66da4a041b30c114327cd3d6c8..c994ff5b157cd47e451065f6db3ea8ac5dad9d4e 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1035,6 +1035,7 @@ enum bpf_attach_type {
        BPF_TRACE_KPROBE_MULTI,
        BPF_LSM_CGROUP,
        BPF_STRUCT_OPS,
+       BPF_NETFILTER,
        __MAX_BPF_ATTACH_TYPE
 };
 

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 14f39c1e573ee527d801a71789f45344906ac7c5..0c21d0d8efe492d32ea6b87483eccd8fb1e4bcd3 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2433,6 +2433,10 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
                default:
                        return -EINVAL;
                }
+       case BPF_PROG_TYPE_NETFILTER:
+               if (expected_attach_type == BPF_NETFILTER)
+                       return 0;
+               return -EINVAL;
        case BPF_PROG_TYPE_SYSCALL:
        case BPF_PROG_TYPE_EXT:
                if (expected_attach_type)
@@ -4590,7 +4594,12 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
 
        switch (prog->type) {
        case BPF_PROG_TYPE_EXT:
+               break;
        case BPF_PROG_TYPE_NETFILTER:
+               if (attr->link_create.attach_type != BPF_NETFILTER) {
+                       ret = -EINVAL;
+                       goto out;
+               }
                break;
        case BPF_PROG_TYPE_PERF_EVENT:
        case BPF_PROG_TYPE_TRACEPOINT:

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 1bb11a6ee6676b66da4a041b30c114327cd3d6c8..c994ff5b157cd47e451065f6db3ea8ac5dad9d4e 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1035,6 +1035,7 @@ enum bpf_attach_type {
        BPF_TRACE_KPROBE_MULTI,
        BPF_LSM_CGROUP,
        BPF_STRUCT_OPS,
+       BPF_NETFILTER,
        __MAX_BPF_ATTACH_TYPE
 };
 

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ad1ec893b41b2c91fd58ada2326d3f01dcb5f5d8..a27f6e9ccce75f07ab11501d1872dd0b2bd12f2f 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -117,6 +117,7 @@ static const char * const attach_type_name[] = {
        [BPF_PERF_EVENT]                = "perf_event",
        [BPF_TRACE_KPROBE_MULTI]        = "trace_kprobe_multi",
        [BPF_STRUCT_OPS]                = "struct_ops",
+       [BPF_NETFILTER]                 = "netfilter",
 };
 
 static const char * const link_type_name[] = {
@@ -8712,7 +8713,7 @@ static const struct bpf_sec_def section_defs[] = {
        SEC_DEF("struct_ops+",          STRUCT_OPS, 0, SEC_NONE),
        SEC_DEF("struct_ops.s+",        STRUCT_OPS, 0, SEC_SLEEPABLE),
        SEC_DEF("sk_lookup",            SK_LOOKUP, BPF_SK_LOOKUP, SEC_ATTACHABLE),
-       SEC_DEF("netfilter",            NETFILTER, 0, SEC_NONE),
+       SEC_DEF("netfilter",            NETFILTER, BPF_NETFILTER, SEC_NONE),
 };
 
 static size_t custom_sec_def_cnt;

diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 6065f408a59c1ccab4ed072bed8c6f766dc671d6..b7d443129f1cdce3fcf479fa9e5305ae6f031156 100644 (file)
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -180,7 +180,9 @@ static int probe_prog_load(enum bpf_prog_type prog_type,
        case BPF_PROG_TYPE_SK_REUSEPORT:
        case BPF_PROG_TYPE_FLOW_DISSECTOR:
        case BPF_PROG_TYPE_CGROUP_SYSCTL:
+               break;
        case BPF_PROG_TYPE_NETFILTER:
+               opts.expected_attach_type = BPF_NETFILTER;
                break;
        default:
                return -EOPNOTSUPP;