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Date: Sat, 8 Jan 2022 13:47:39 +0000 From: Yafang Shao <laoar.shao@...il.com> To: daniel@...earbox.net, ast@...nel.org, andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, Yafang Shao <laoar.shao@...il.com> Subject: [PATCH] libbpf: fix possible NULL pointer dereference when destroy skelton When I checked the code in skelton header file generated with my own bpf prog, I found there may be possible NULL pointer derefence when destroy skelton. 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: d66562fba ("libbpf: Add BPF object skeleton support") Signed-off-by: Yafang Shao <laoar.shao@...il.com> Cc: Andrii Nakryiko <andrii@...nel.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 7c74342bb668..a07fbd59e4b8 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11464,6 +11464,9 @@ 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) -- 2.17.1
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