On Fri, May 24, 2024 at 03:06 PM +02, Jakub Sitnicki wrote: > 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. > > [...] Posted: https://lore.kernel.org/r/20240527-sockmap-verify-deletes-v1-0-944b372f2101@xxxxxxxxxxxxxx
