From: John Fastabend <john.fastabend@gmail.com>
To: Jakub Sitnicki <jakub@cloudflare.com>,
Cong Wang <xiyou.wangcong@gmail.com>
Cc: netdev@vger.kernel.org, Cong Wang <cong.wang@bytedance.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
John Fastabend <john.fastabend@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Lorenz Bauer <lmb@cloudflare.com>
Subject: Re: [Patch bpf-next] unix_bpf: fix a potential deadlock in unix_dgram_bpf_recvmsg()
Date: Wed, 28 Jul 2021 11:52:44 -0700 [thread overview]
Message-ID: <6101a77ca9c1_1e1ff620822@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <87h7ge3fya.fsf@cloudflare.com>
Jakub Sitnicki wrote:
> On Fri, Jul 23, 2021 at 08:36 PM CEST, Cong Wang wrote:
> > From: Cong Wang <cong.wang@bytedance.com>
> >
> > As Eric noticed, __unix_dgram_recvmsg() may acquire u->iolock
> > too, so we have to release it before calling this function.
> >
> > Fixes: 9825d866ce0d ("af_unix: Implement unix_dgram_bpf_recvmsg()")
> > Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
> > Cc: John Fastabend <john.fastabend@gmail.com>
> > Cc: Daniel Borkmann <daniel@iogearbox.net>
> > Cc: Jakub Sitnicki <jakub@cloudflare.com>
> > Cc: Lorenz Bauer <lmb@cloudflare.com>
> > Signed-off-by: Cong Wang <cong.wang@bytedance.com>
> > ---
> > net/unix/unix_bpf.c | 11 ++++++-----
> > 1 file changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/unix/unix_bpf.c b/net/unix/unix_bpf.c
> > index db0cda29fb2f..b07cb30e87b1 100644
> > --- a/net/unix/unix_bpf.c
> > +++ b/net/unix/unix_bpf.c
> > @@ -53,8 +53,9 @@ static int unix_dgram_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
> > mutex_lock(&u->iolock);
> > if (!skb_queue_empty(&sk->sk_receive_queue) &&
> > sk_psock_queue_empty(psock)) {
> > - ret = __unix_dgram_recvmsg(sk, msg, len, flags);
> > - goto out;
> > + mutex_unlock(&u->iolock);
> > + sk_psock_put(sk, psock);
> > + return __unix_dgram_recvmsg(sk, msg, len, flags);
> > }
> >
> > msg_bytes_ready:
> > @@ -68,13 +69,13 @@ static int unix_dgram_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
> > if (data) {
> > if (!sk_psock_queue_empty(psock))
> > goto msg_bytes_ready;
> > - ret = __unix_dgram_recvmsg(sk, msg, len, flags);
> > - goto out;
> > + mutex_unlock(&u->iolock);
> > + sk_psock_put(sk, psock);
> > + return __unix_dgram_recvmsg(sk, msg, len, flags);
> > }
> > copied = -EAGAIN;
> > }
> > ret = copied;
> > -out:
> > mutex_unlock(&u->iolock);
> > sk_psock_put(sk, psock);
> > return ret;
>
> Nit: Can be just `return copied`. `ret` became useless.
>
> Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Worth doing the small cleanup pointed out by Jakub but feel free to add
my ack.
Acked-by: John Fastabend <john.fastabend@gmail.com>
next prev parent reply other threads:[~2021-07-28 18:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 18:36 [Patch bpf-next] unix_bpf: fix a potential deadlock in unix_dgram_bpf_recvmsg() Cong Wang
2021-07-27 16:12 ` John Fastabend
2021-07-28 3:06 ` Cong Wang
2021-07-28 10:12 ` Jakub Sitnicki
2021-07-28 18:52 ` John Fastabend [this message]
2021-07-30 19:45 ` Andrii Nakryiko
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