Messages in this thread | | | Subject | Re: [PATCH 1/1] AF_UNIX: Fix poll locking problem when reading from a stream socket | From | Eric Dumazet <> | Date | Tue, 22 Nov 2011 06:23:01 +0100 |
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Le mardi 22 novembre 2011 à 03:35 +0400, Alexey Moiseytsev a écrit : > poll() call may be locked by concurrent reading from the same stream > socket. > > Signed-off-by: Alexey Moiseytsev <himeraster@gmail.com> > --- > net/unix/af_unix.c | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) > > diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c > index 466fbcc..b595a3d 100644 > --- a/net/unix/af_unix.c > +++ b/net/unix/af_unix.c > @@ -1957,6 +1957,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, > if ((UNIXCB(skb).pid != siocb->scm->pid) || > (UNIXCB(skb).cred != siocb->scm->cred)) { > skb_queue_head(&sk->sk_receive_queue, skb); > + sk->sk_data_ready(sk, skb->len); > break; > } > } else { > @@ -1974,6 +1975,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, > chunk = min_t(unsigned int, skb->len, size); > if (memcpy_toiovec(msg->msg_iov, skb->data, chunk)) { > skb_queue_head(&sk->sk_receive_queue, skb); > + sk->sk_data_ready(sk, skb->len); > if (copied == 0) > copied = -EFAULT; > break; > @@ -1991,6 +1993,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, > /* put the skb back if we didn't use it up.. */ > if (skb->len) { > skb_queue_head(&sk->sk_receive_queue, skb); > + sk->sk_data_ready(sk, skb->len); > break; > } > > @@ -2006,6 +2009,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, > > /* put message back and return */ > skb_queue_head(&sk->sk_receive_queue, skb); > + sk->sk_data_ready(sk, skb->len); > break; > } > } while (size);
Fine, the fix is technically correct since we own u->readlock mutex, another thread cannot consume the just requeued skb.
Small note : the words "locking" and "locked" are more used to describe the action of taking a spinlock/mutex/rwlock or something, while the bug you fixed is more about poll() system call being blocked/frozen forever.
Thanks !
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
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