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tcp: fix recv with flags MSG_WAITALL | MSG_PEEK

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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: Enrico Scholz <rh-bugzilla@ensc.de>
Reported-by: Dan Searle <dan@censornet.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Sabrina Dubroca 2015-07-24 18:19:25 +02:00 • committed by David S. Miller
parent 3d3af88592
commit dfbafc9953
5 changed files with 14 additions and 10 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
include/net/sock.h
View file

@ -902,7 +902,7 @@ void sk_stream_kill_queues(struct sock *sk);
void sk_set_memalloc(struct sock *sk); void sk_set_memalloc(struct sock *sk);
void sk_clear_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 request_sock_ops;
struct timewait_sock_ops; struct timewait_sock_ops;

5
net/core/sock.c
View file

@ -1967,20 +1967,21 @@ static void __release_sock(struct sock *sk)
* sk_wait_data - wait for data to arrive at sk_receive_queue * sk_wait_data - wait for data to arrive at sk_receive_queue
* @sk: sock to wait on * @sk: sock to wait on
* @timeo: for how long * @timeo: for how long
* @skb: last skb seen on sk_receive_queue
* *
* Now socket state including sk->sk_err is changed only under lock, * Now socket state including sk->sk_err is changed only under lock,
* hence we may omit checks after joining wait queue. * hence we may omit checks after joining wait queue.
* We check receive queue before schedule() only as optimization; * We check receive queue before schedule() only as optimization;
* it is very likely that release_sock() added new data. * 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; int rc;
DEFINE_WAIT(wait); DEFINE_WAIT(wait);
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE); prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
set_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags); 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); clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
finish_wait(sk_sleep(sk), &wait); finish_wait(sk_sleep(sk), &wait);
return rc; return rc;

2
net/dccp/proto.c
View file

@ -886,7 +886,7 @@ verify_sock_status:
break; break;
} }
sk_wait_data(sk, &timeo); sk_wait_data(sk, &timeo, NULL);
continue; continue;
found_ok_skb: found_ok_skb:
if (len > skb->len) if (len > skb->len)

11
net/ipv4/tcp.c
View file

@ -780,7 +780,7 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
ret = -EAGAIN; ret = -EAGAIN;
break; break;
} }
sk_wait_data(sk, &timeo); sk_wait_data(sk, &timeo, NULL);
if (signal_pending(current)) { if (signal_pending(current)) {
ret = sock_intr_errno(timeo); ret = sock_intr_errno(timeo);
break; 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 */ int target; /* Read at least this many bytes */
long timeo; long timeo;
struct task_struct *user_recv = NULL; struct task_struct *user_recv = NULL;
struct sk_buff *skb; struct sk_buff *skb, *last;
u32 urg_hole = 0; u32 urg_hole = 0;
if (unlikely(flags & MSG_ERRQUEUE)) 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. */ /* Next get a buffer. */
last = skb_peek_tail(&sk->sk_receive_queue);
skb_queue_walk(&sk->sk_receive_queue, skb) { skb_queue_walk(&sk->sk_receive_queue, skb) {
last = skb;
/* Now that we have two receive queues this /* Now that we have two receive queues this
* shouldn't happen. * 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. */ /* Do not sleep, just process backlog. */
release_sock(sk); release_sock(sk);
lock_sock(sk); lock_sock(sk);
} else } else {
sk_wait_data(sk, &timeo); sk_wait_data(sk, &timeo, last);
}
if (user_recv) { if (user_recv) {
int chunk; int chunk;

4
net/llc/af_llc.c
View file

@ -613,7 +613,7 @@ static int llc_wait_data(struct sock *sk, long timeo)
if (signal_pending(current)) if (signal_pending(current))
break; break;
rc = 0; rc = 0;
if (sk_wait_data(sk, &timeo)) if (sk_wait_data(sk, &timeo, NULL))
break; break;
} }
return rc; return rc;
@ -802,7 +802,7 @@ static int llc_ui_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
release_sock(sk); release_sock(sk);
lock_sock(sk); lock_sock(sk);
} else } else
sk_wait_data(sk, &timeo); sk_wait_data(sk, &timeo, NULL);
if ((flags & MSG_PEEK) && peek_seq != llc->copied_seq) { if ((flags & MSG_PEEK) && peek_seq != llc->copied_seq) {
net_dbg_ratelimited("LLC(%s:%d): Application bug, race in MSG_PEEK\n", net_dbg_ratelimited("LLC(%s:%d): Application bug, race in MSG_PEEK\n",