From: Yafang Shao <laoar.shao@xxxxxxxxx>
[ Upstream commit a32ea51a3f17ce6524c9fc19d311e708331c8b5f ]
When I checked the code in skeleton header file generated with my own
bpf prog, I found there may be possible NULL pointer dereference when
destroying skeleton. Then I checked the in-tree bpf progs, finding that is
a common issue. Let's take the generated samples/bpf/xdp_redirect_cpu.skel.h
for example. Below is the generated code in
xdp_redirect_cpu__create_skeleton():
xdp_redirect_cpu__create_skeleton
struct bpf_object_skeleton *s;
s = (struct bpf_object_skeleton *)calloc(1, sizeof(*s));
if (!s)
goto error;
...
error:
bpf_object__destroy_skeleton(s);
return -ENOMEM;
After goto error, the NULL 's' will be deferenced in
bpf_object__destroy_skeleton().
We can simply fix this issue by just adding a NULL check in
bpf_object__destroy_skeleton().
Fixes: d66562fba1ce ("libbpf: Add BPF object skeleton support")
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20220108134739.32541-1-laoar.shao@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7f10dd501a52..fdb3536afa7d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11795,6 +11795,9 @@ void bpf_object__detach_skeleton(struct bpf_object_skeleton *s)
void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s)
{
+ if (!s)
+ return;
+
if (s->progs)
bpf_object__detach_skeleton(s);
if (s->obj)
--
2.34.1
