Re: [PATCH bpf] bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data()

[Jiayuan Chen <jiayuan.chen@linux.dev>]

On 4/25/26 3:16 AM, Weiming Shi wrote:
> When the scatterlist ring is full or nearly full, bpf_msg_push_data()
> enters a copy fallback path and computes copy + len for the page
> allocation size. Since len comes from BPF with arg3_type = ARG_ANYTHING
> and both are u32, a crafted len can wrap the sum to a small value,
> causing an undersized allocation followed by an out-of-bounds memcpy.
>
>   BUG: unable to handle page fault for address: ffffed104089a402
>   Oops: Oops: 0000 [#1] SMP KASAN NOPTI
>   Call Trace:
>    __asan_memcpy (mm/kasan/shadow.c:105)
>    bpf_msg_push_data (net/core/filter.c:2852 net/core/filter.c:2788)
>    bpf_prog_9ed8b5711920a7d7+0x2e/0x36
>    sk_psock_msg_verdict (net/core/skmsg.c:934)
>    tcp_bpf_sendmsg (net/ipv4/tcp_bpf.c:421 net/ipv4/tcp_bpf.c:584)
>    __sys_sendto (net/socket.c:2206)
>    do_syscall_64 (arch/x86/entry/syscall_64.c:94)
>    entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
>
> Add an overflow check before the allocation.
>
> Link: https://lore.kernel.org/all/20260424155913.A19FDC19425@smtp.kernel.org
> Fixes: 6fff607e2f14 ("bpf: sk_msg program helper bpf_msg_push_data")
> Tested-by: Xiang Mei <xmei5@asu.edu>
> Tested-by: Xinyu Ma <mmmxny@gmail.com>
> Signed-off-by: Weiming Shi <bestswngs@gmail.com>


Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>