On Wed, May 22, 2024 at 07:57 AM -07, Alexei Starovoitov wrote: > On Wed, May 22, 2024 at 5:12 AM Jakub Sitnicki <jakub@xxxxxxxxxxxxxx> wrote: >> >> On Wed, May 22, 2024 at 07:33 PM +08, Hillf Danton wrote: >> > On Wed, 22 May 2024 11:50:49 +0200 Jakub Sitnicki <jakub@xxxxxxxxxxxxxx> >> > On Wed, May 22, 2024 at 06:59 AM +08, Hillf Danton wrote: >> >> > On Tue, 21 May 2024 08:38:52 -0700 Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> >> >> >> On Sun, May 12, 2024 at 12:22=E2=80=AFAM Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: >> >> >> > --- a/net/core/sock_map.c >> >> >> > +++ b/net/core/sock_map.c >> >> >> > @@ -142,6 +142,7 @@ static void sock_map_del_link(struct sock *sk, >> >> >> > bool strp_stop =3D false, verdict_stop =3D false; >> >> >> > struct sk_psock_link *link, *tmp; >> >> >> > >> >> >> > + rcu_read_lock(); >> >> >> > spin_lock_bh(&psock->link_lock); >> >> >> >> >> >> I think this is incorrect. >> >> >> spin_lock_bh may sleep in RT and it won't be safe to do in rcu cs. >> >> > >> >> > Could you specify why it won't be safe in rcu cs if you are right? >> >> > What does rcu look like in RT if not nothing? >> >> >> >> RCU readers can't block, while spinlock RT doesn't disable preemption. >> >> >> >> https://docs.kernel.org/RCU/rcu.html >> >> https://docs.kernel.org/locking/locktypes.html#spinlock-t-and-preempt-rt >> >> >> >> I've finally gotten around to testing proposed fix that just disallows >> >> map_delete_elem on sockmap/sockhash from BPF tracing progs >> >> completely. This should put an end to this saga of syzkaller reports. >> >> >> >> https://lore.kernel.org/all/87jzjnxaqf.fsf@xxxxxxxxxxxxxx/ > > Agree. Let's do that. According to John the delete path is not something > that is used in production. It's only a source of trouble with syzbot. Cool. The proposed API rule would be that if a BPF program type is allowed to update a sockmap/sockhash, then it is also allowed to delete from it. So I need to tweak my patch to allow deletes from sock_ops progs. We have a dedicated bpf_sock_map_update() helper there. [...]
