Re: Is xt_owner's owner_mt() racy with sock_orphan()? [worse with new TYPESAFE_BY_RCU file lifetime?]

[Jann Horn]

On Tue, Dec 5, 2023 at 5:40 PM Jann Horn <jannh@xxxxxxxxxx> wrote:
>
> Hi!
>
> I think this code is racy, but testing that seems like a pain...
>
> owner_mt() in xt_owner runs in context of a NF_INET_LOCAL_OUT or
> NF_INET_POST_ROUTING hook. It first checks that sk->sk_socket is
> non-NULL, then checks that sk->sk_socket->file is non-NULL, then
> accesses the ->f_cred of that file.
>
> I don't see anything that protects this against a concurrent
> sock_orphan(), which NULLs out the sk->sk_socket pointer, if we're in

Ah, and all the other users of ->sk_socket in net/netfilter/ do it
under the sk_callback_lock... so I guess the fix would be to add the
same in owner_mt?