bpf: include sub program tags in bpf_prog_info

Changes v2 -> v3:
1. remove check for bpf_dump_raw_ok().

Changes v1 -> v2:
1. Fix error path as Martin suggested.

This patch adds nr_prog_tags and prog_tags to bpf_prog_info. This is a
reliable way for user space to get tags of all sub programs. Before this
patch, user space need to find sub program tags via kallsyms.

This feature will be used in BPF introspection, where user space queries
information about BPF programs via sys_bpf.

Signed-off-by: Song Liu <songliubraving@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 22 insertions, 0 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index b7c585838c72..7f1410d6fbe9 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2315,6 +2315,28 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
                 }
         }
 
+        ulen = info.nr_prog_tags;
+        info.nr_prog_tags = prog->aux->func_cnt ? : 1;
+        if (ulen) {
+                __u8 __user (*user_prog_tags)[BPF_TAG_SIZE];
+                u32 i;
+
+                user_prog_tags = u64_to_user_ptr(info.prog_tags);
+                ulen = min_t(u32, info.nr_prog_tags, ulen);
+                if (prog->aux->func_cnt) {
+                        for (i = 0; i < ulen; i++) {
+                                if (copy_to_user(user_prog_tags[i],
+                                                 prog->aux->func[i]->tag,
+                                                 BPF_TAG_SIZE))
+                                        return -EFAULT;
+                        }
+                } else {
+                        if (copy_to_user(user_prog_tags[0],
+                                         prog->tag, BPF_TAG_SIZE))
+                                return -EFAULT;
+                }
+        }
+
 done:
         if (copy_to_user(uinfo, &info, info_len) ||
             put_user(info_len, &uattr->info.info_len))