Re: [PATCH net] bpf, sockmap: Restore sk_prot ops when psock is removed from sockmap

[Cong Wang <xiyou.wangcong@gmail.com>]

On Wed, Mar 05, 2025 at 10:02:34PM +0800, Dong Chenchen wrote:
> WARNING: CPU: 0 PID: 6558 at net/core/sock_map.c:1703 sock_map_close+0x3c4/0x480
> Modules linked in:
> CPU: 0 UID: 0 PID: 6558 Comm: syz-executor.14 Not tainted 6.14.0-rc5+ #238
> RIP: 0010:sock_map_close+0x3c4/0x480
> Call Trace:
>  <TASK>
>  inet_release+0x144/0x280
>  __sock_release+0xb8/0x270
>  sock_close+0x1e/0x30
>  __fput+0x3c6/0xb30
>  __fput_sync+0x7b/0x90
>  __x64_sys_close+0x90/0x120
>  do_syscall_64+0x5d/0x170
>  entry_SYSCALL_64_after_hwframe+0x76/0x7e
> 
> The root cause is:
> sock_hash_update_common
>   sock_map_unref
>     sock_map_del_link
>       psock->psock_update_sk_prot(sk, psock, false);
> 	//false won't restore proto
>     sk_psock_put
>        rcu_assign_sk_user_data(sk, NULL);
> inet_release
>   sk->sk_prot->close
>     sock_map_close
>       WARN(sk->sk_prot->close == sock_map_close)
> 
> When psock is removed from sockmap, sock_map_del_link() still set
> sk->sk_prot to bpf proto instead of restore it (for incorrect restore
> value). sock release will triger warning of sock_map_close() for
> recurse after psock drop.

But sk_psock_drop() restores it with sk_psock_restore_proto() after the
psock reference count goes to zero. So how could the above happen?

By the way, it would be perfect if you could add a test case for it 
together with this patch (a followup patch is fine too).

Thanks!