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

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=1205258


Reported-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

include/net/sock.h

+1 −1
Original line number Diff line number Diff line
@@ -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;

net/core/sock.c

+3 −2
Original line number Diff line number Diff line
@@ -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;

net/dccp/proto.c

+1 −1
Original line number Diff line number Diff line
@@ -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)

net/ipv4/tcp.c

+7 −4
Original line number Diff line number Diff line
@@ -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;

net/llc/af_llc.c

+2 −2
Original line number Diff line number Diff line
@@ -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",