[PATCH bpf] bpf: Fix NULL pointer dereference in bpf_sock_from_file
From: MahnurA <hidden>
Date: 2026-08-18 17:43:04
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [networking] (tcx & tc bpf, sock_addr), networking [general], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
bpf_sock_from_file should not dereference a NULL file pointer.
KASAN detects a null-ptr-deref when eBPF tracing
fentry/fexit programs are attached to points such as
__mmap_region and file_map_prot_check kernel functions. This can
result in a NULL file pointer flowing from context to the helper.
A minimal check before dereferencing can fix this.
Fixes: b60da4955f53 ("bpf: Only provide bpf_sock_from_file with CONFIG_NET")
Signed-off-by: MahnurA <redacted>
---
net/core/filter.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index 16845987b244..7c3caae4bafc 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c@@ -12182,7 +12182,10 @@ const struct bpf_func_proto bpf_skc_to_mptcp_sock_proto = { BPF_CALL_1(bpf_sock_from_file, struct file *, file) { - return (unsigned long)sock_from_file(file); + if (file) + return (unsigned long)sock_from_file(file); + + return (unsigned long)NULL; } BTF_ID_LIST(bpf_sock_from_file_btf_ids)
--
2.53.0