From: Alexei Starovoitov <ast@kernel.org>
Date: Tue, 26 Nov 2019 15:01:06 -0800
Subject: bpf: Fix static checker warning
Patch-mainline: v5.5-rc1
Git-commit: d0f010434124598988ba1c97fbb0e4e820ff5d8c
References: bsc#1154353

kernel/bpf/btf.c:4023 btf_distill_func_proto()
        error: potentially dereferencing uninitialized 't'.

kernel/bpf/btf.c
  4012          nargs = btf_type_vlen(func);
  4013          if (nargs >= MAX_BPF_FUNC_ARGS) {
  4014                  bpf_log(log,
  4015                          "The function %s has %d arguments. Too many.\n",
  4016                          tname, nargs);
  4017                  return -EINVAL;
  4018          }
  4019          ret = __get_type_size(btf, func->type, &t);
                                                       ^^
t isn't initialized for the first -EINVAL return

This is unlikely path, since BTF should have been validated at this point.
Fix it by returning 'void' BTF.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191126230106.237179-1-ast@kernel.org
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 kernel/bpf/btf.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3953,8 +3953,10 @@ static int __get_type_size(struct btf *b
 	t = btf_type_by_id(btf, btf_id);
 	while (t && btf_type_is_modifier(t))
 		t = btf_type_by_id(btf, t->type);
-	if (!t)
+	if (!t) {
+		*bad_type = btf->types[0];
 		return -EINVAL;
+	}
 	if (btf_type_is_ptr(t))
 		/* kernel size of pointer. Not BPF's size of pointer*/
 		return sizeof(void *);