From: John Fastabend <john.fastabend@gmail.com>
To: Cong Wang <xiyou.wangcong@gmail.com>, netdev@vger.kernel.org
Cc: Cong Wang <cong.wang@bytedance.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
John Fastabend <john.fastabend@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Jakub Sitnicki <jakub@cloudflare.com>,
Lorenz Bauer <lmb@cloudflare.com>
Subject: RE: [Patch bpf-next] unix_bpf: fix a potential deadlock in unix_dgram_bpf_recvmsg()
Date: Tue, 27 Jul 2021 09:12:17 -0700 [thread overview]
Message-ID: <610030612aaa3_199a412083d@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <20210723183630.5088-1-xiyou.wangcong@gmail.com>
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);
> }
Is there a reason to grab the mutex_lock(u->iolock) above the
skb_queue_emptyaand sk_psock_queue_empty checks?
Could it be move here just above the msg_bytes_ready label?
>
> 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;
> --
> 2.27.0
>
next prev parent reply other threads:[~2021-07-27 16:12 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 [this message]
2021-07-28 3:06 ` Cong Wang
2021-07-28 10:12 ` Jakub Sitnicki
2021-07-28 18:52 ` John Fastabend
2021-07-30 19:45 ` Andrii Nakryiko
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