Re: [PATCH bpf] bpf: Fix NULL pointer dereference in bpf_sock_from_file
From: "Emil Tsalapatis" <emil@etsalapatis.com>
Date: 2026-08-19 19:44:21
Also in:
bpf
On Tue Aug 18, 2026 at 1:42 PM EDT, MahnurA wrote:
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>Patch looks fine and the crash replicates. Please resend with a full name since we don't take pseudonymous contributions. Once you do, please feel free to add my reviewed-by tag. pw-bot: cr
quoted hunk ↗ jump to hunk
--- 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)