From: Yafang Shao laoar.shao@gmail.com
[ 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@gmail.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20220108134739.32541-1-laoar.shao@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c7ba5e6ed9cf..23edb41637d4 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11497,6 +11497,9 @@ 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)