Commit dfbafc99 authored by Sabrina Dubroca's avatar Sabrina Dubroca Committed by David S. Miller

tcp: fix recv with flags MSG_WAITALL | MSG_PEEK

Currently, tcp_recvmsg enters a busy loop in sk_wait_data if called
with flags = MSG_WAITALL | MSG_PEEK.

sk_wait_data waits for sk_receive_queue not empty, but in this case,
the receive queue is not empty, but does not contain any skb that we
can use.

Add a "last skb seen on receive queue" argument to sk_wait_data, so
that it sleeps until the receive queue has new skbs.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=99461
Link: https://sourceware.org/bugzilla/show_bug.cgi?id=18493
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1205258Reported-by: default avatarEnrico Scholz <rh-bugzilla@ensc.de>
Reported-by: default avatarDan Searle <dan@censornet.com>
Signed-off-by: default avatarSabrina Dubroca <sd@queasysnail.net>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3d3af885
......@@ -902,7 +902,7 @@ void sk_stream_kill_queues(struct sock *sk);
void sk_set_memalloc(struct sock *sk);
void sk_clear_memalloc(struct sock *sk);
int sk_wait_data(struct sock *sk, long *timeo);
int sk_wait_data(struct sock *sk, long *timeo, const struct sk_buff *skb);
struct request_sock_ops;
struct timewait_sock_ops;
......
......@@ -1967,20 +1967,21 @@ static void __release_sock(struct sock *sk)
* sk_wait_data - wait for data to arrive at sk_receive_queue
* @sk: sock to wait on
* @timeo: for how long
* @skb: last skb seen on sk_receive_queue
*
* Now socket state including sk->sk_err is changed only under lock,
* hence we may omit checks after joining wait queue.
* We check receive queue before schedule() only as optimization;
* it is very likely that release_sock() added new data.
*/
int sk_wait_data(struct sock *sk, long *timeo)
int sk_wait_data(struct sock *sk, long *timeo, const struct sk_buff *skb)
{
int rc;
DEFINE_WAIT(wait);
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
set_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
rc = sk_wait_event(sk, timeo, !skb_queue_empty(&sk->sk_receive_queue));
rc = sk_wait_event(sk, timeo, skb_peek_tail(&sk->sk_receive_queue) != skb);
clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
finish_wait(sk_sleep(sk), &wait);
return rc;
......
......@@ -886,7 +886,7 @@ int dccp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
break;
}
sk_wait_data(sk, &timeo);
sk_wait_data(sk, &timeo, NULL);
continue;
found_ok_skb:
if (len > skb->len)
......
......@@ -780,7 +780,7 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
ret = -EAGAIN;
break;
}
sk_wait_data(sk, &timeo);
sk_wait_data(sk, &timeo, NULL);
if (signal_pending(current)) {
ret = sock_intr_errno(timeo);
break;
......@@ -1575,7 +1575,7 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
int target; /* Read at least this many bytes */
long timeo;
struct task_struct *user_recv = NULL;
struct sk_buff *skb;
struct sk_buff *skb, *last;
u32 urg_hole = 0;
if (unlikely(flags & MSG_ERRQUEUE))
......@@ -1635,7 +1635,9 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
/* Next get a buffer. */
last = skb_peek_tail(&sk->sk_receive_queue);
skb_queue_walk(&sk->sk_receive_queue, skb) {
last = skb;
/* Now that we have two receive queues this
* shouldn't happen.
*/
......@@ -1754,8 +1756,9 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
/* Do not sleep, just process backlog. */
release_sock(sk);
lock_sock(sk);
} else
sk_wait_data(sk, &timeo);
} else {
sk_wait_data(sk, &timeo, last);
}
if (user_recv) {
int chunk;
......
......@@ -613,7 +613,7 @@ static int llc_wait_data(struct sock *sk, long timeo)
if (signal_pending(current))
break;
rc = 0;
if (sk_wait_data(sk, &timeo))
if (sk_wait_data(sk, &timeo, NULL))
break;
}
return rc;
......@@ -802,7 +802,7 @@ static int llc_ui_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
release_sock(sk);
lock_sock(sk);
} else
sk_wait_data(sk, &timeo);
sk_wait_data(sk, &timeo, NULL);
if ((flags & MSG_PEEK) && peek_seq != llc->copied_seq) {
net_dbg_ratelimited("LLC(%s:%d): Application bug, race in MSG_PEEK\n",
......
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