[PATCH bpf-next] libbf: fix uninitialized pointer at btf__parse_raw()

Recently, from commit 94a1fedd63ed ("libbpf: Add btf__parse_raw() and
generic btf__parse() APIs"), new API has been added to libbpf that
allows to parse BTF from raw data file (btf__parse_raw()).

The commit derives build failure of samples/bpf due to improper access
of uninitialized pointer at btf_parse_raw().

    btf.c: In function btf__parse_raw:
    btf.c:625:28: error: btf may be used uninitialized in this function
      625 |  return err ? ERR_PTR(err) : btf;
          |         ~~~~~~~~~~~~~~~~~~~^~~~~

This commit fixes the build failure of samples/bpf by adding code of
initializing btf pointer as NULL.

Fixes: 94a1fedd63ed ("libbpf: Add btf__parse_raw() and generic btf__parse() APIs")
Signed-off-by: Daniel T. Lee <redacted>
---
 tools/lib/bpf/btf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 856b09a04563..4843e44916f7 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c

@@ -564,8 +564,8 @@ struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext)
 
 struct btf *btf__parse_raw(const char *path)
 {
+	struct btf *btf = NULL;
 	void *data = NULL;
-	struct btf *btf;
 	FILE *f = NULL;
 	__u16 magic;
 	int err = 0;

-- 
2.25.1

Daniel T. Lee wrote:

Recently, from commit 94a1fedd63ed ("libbpf: Add btf__parse_raw() and
generic btf__parse() APIs"), new API has been added to libbpf that
allows to parse BTF from raw data file (btf__parse_raw()).

The commit derives build failure of samples/bpf due to improper access
of uninitialized pointer at btf_parse_raw().

    btf.c: In function btf__parse_raw:
    btf.c:625:28: error: btf may be used uninitialized in this function
      625 |  return err ? ERR_PTR(err) : btf;
          |         ~~~~~~~~~~~~~~~~~~~^~~~~

This commit fixes the build failure of samples/bpf by adding code of
initializing btf pointer as NULL.

Fixes: 94a1fedd63ed ("libbpf: Add btf__parse_raw() and generic btf__parse() APIs")
Signed-off-by: Daniel T. Lee <redacted>
---

Unless errno is zero this should be ok in practice, but I guess compiler
wont know that.

Acked-by: John Fastabend <john.fastabend@gmail.com>

On Wed, Aug 5, 2020 at 11:22 PM John Fastabend [off-list ref] wrote:

Daniel T. Lee wrote:

quoted

Recently, from commit 94a1fedd63ed ("libbpf: Add btf__parse_raw() and
generic btf__parse() APIs"), new API has been added to libbpf that
allows to parse BTF from raw data file (btf__parse_raw()).

The commit derives build failure of samples/bpf due to improper access
of uninitialized pointer at btf_parse_raw().

    btf.c: In function btf__parse_raw:
    btf.c:625:28: error: btf may be used uninitialized in this function
      625 |  return err ? ERR_PTR(err) : btf;
          |         ~~~~~~~~~~~~~~~~~~~^~~~~

This commit fixes the build failure of samples/bpf by adding code of
initializing btf pointer as NULL.

Fixes: 94a1fedd63ed ("libbpf: Add btf__parse_raw() and generic btf__parse() APIs")
Signed-off-by: Daniel T. Lee <redacted>
---

Unless errno is zero this should be ok in practice, but I guess compiler
wont know that.

Acked-by: John Fastabend <john.fastabend@gmail.com>

Applied. Thanks