[PATCH AUTOSEL 5.1 197/219] bpf, libbpf, smatch: Fix potential NULL pointer dereference

Sasha Levin
2019-07-15T14:16:01Z

From: Leo Yan <leo.yan@linaro.org>

[ Upstream commit 33bae185f74d49a0d7b1bfaafb8e959efce0f243 ]

Based on the following report from Smatch, fix the potential NULL
pointer dereference check:

tools/lib/bpf/libbpf.c:3493
bpf_prog_load_xattr() warn: variable dereferenced before check 'attr'
(see line 3483)

3479 int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
3480 struct bpf_object **pobj, int *prog_fd)
3481 {
3482 struct bpf_object_open_attr open_attr = {
3483 .file = attr->file,
3484 .prog_type = attr->prog_type,
^^^^^^
3485 };

At the head of function, it directly access 'attr' without checking
if it's NULL pointer. This patch moves the values assignment after
validating 'attr' and 'attr->file'.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/lib/bpf/libbpf.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 11c25d9ea431..43dc8a8e9105 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2897,10 +2897,7 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
struct bpf_object **pobj, int *prog_fd)
{
- struct bpf_object_open_attr open_attr = {
- .file = attr->file,
- .prog_type = attr->prog_type,
- };
+ struct bpf_object_open_attr open_attr = {};
struct bpf_program *prog, *first_prog = NULL;
enum bpf_attach_type expected_attach_type;
enum bpf_prog_type prog_type;
@@ -2913,6 +2910,9 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
if (!attr->file)
return -EINVAL;

+ open_attr.file = attr->file;
+ open_attr.prog_type = attr->prog_type;
+
obj = bpf_object__open_xattr(&open_attr);
if (IS_ERR_OR_NULL(obj))
return -ENOENT;
--
2.20.1