Re: [PATCH bpf v2 1/3] bpf: Fix out-of-bounds read of sk_protocol in bpf_sock_destroy()

[Kuniyuki Iwashima]

On Sun, Sep 6, 2026 at 12:42 AM Jiayuan Chen <jiayuan.chen@xxxxxxxxx> wrote:
>
> sk_protocol lives in struct sock, not in struct sock_common. A timewait
> or request sock handed to bpf_sock_destroy() by the tcp iterator is
> neither, so reading sk->sk_protocol runs past the object:
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in bpf_sock_destroy+0xc7/0xe0
> Read of size 2 at addr ffff8881047d11b4 by task test_progs/428
>
> Tainted: [W]=WARN
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x91/0xf0
>  print_report+0xd1/0x630
>  kasan_report+0xf3/0x130
>  __asan_report_load2_noabort+0x14/0x30
>  bpf_sock_destroy+0xc7/0xe0
>  bpf_prog_c3dd61f9d9cd9f37_iter_tcp6_timewait+0x9f/0xb7
>  bpf_iter_run_prog+0x538/0xde0
>  bpf_iter_tcp_seq_show+0x26b/0x4b0
>  bpf_seq_read+0x424/0x1210
>  vfs_read+0x197/0xe40
>  ksys_read+0x119/0x240
>  __x64_sys_read+0x72/0xc0
>  x64_sys_call+0x647/0x27e0
>  do_syscall_64+0xe5/0x610
>  entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> Only check sk_protocol on full socks. tcp_abort() already knows how to
> deal with TIME_WAIT and NEW_SYN_RECV socks. Also fix the comment, it
> never matched the code.
>
> Fixes: 4ddbcb886268 ("bpf: Add bpf_sock_destroy kfunc")
> Reported-by: Xiang Mei (Microsoft) <xmei5@xxxxxxx>
> Closes: https://lore.kernel.org/bpf/20260702224519.800135-1-xmei5@xxxxxxx/
> Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>

Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>