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

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 1a59cc7ad730c549940a4784459ae7899bc9dd03..cb43cb842e16c9e8f84fc2574d79f8656a640d29 100644 (file)
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4792,6 +4792,11 @@ static int btf_func_proto_check(struct btf_verifier_env *env,
                        break;
                }
 
+               if (btf_type_is_resolve_source_only(arg_type)) {
+                       btf_verifier_log_type(env, t, "Invalid arg#%u", i + 1);
+                       return -EINVAL;
+               }
+
                if (args[i].name_off &&
                    (!btf_name_offset_valid(btf, args[i].name_off) ||
                     !btf_name_valid_identifier(btf, args[i].name_off))) {