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Date: Fri, 24 Jul 2015 18:19:25 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: netdev@...r.kernel.org
Cc: Enrico Scholz <rh-bugzilla@...c.de>,
Dan Searle <dan@...sornet.com>,
Sabrina Dubroca <sd@...asysnail.net>
Subject: [PATCH net] 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: Enrico Scholz <rh-bugzilla@...c.de>
Reported-by: Dan Searle <dan@...sornet.com>
Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
include/net/sock.h | 2 +-
net/core/sock.c | 5 +++--
net/dccp/proto.c | 2 +-
net/ipv4/tcp.c | 11 +++++++----
net/llc/af_llc.c | 4 ++--
5 files changed, 14 insertions(+), 10 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index 05a8c1aea251..f21f0708ec59 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -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;
diff --git a/net/core/sock.c b/net/core/sock.c
index 08f16db46070..8a14f1285fc4 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -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;
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 52a94016526d..b5cf13a28009 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -886,7 +886,7 @@ verify_sock_status:
break;
}
- sk_wait_data(sk, &timeo);
+ sk_wait_data(sk, &timeo, NULL);
continue;
found_ok_skb:
if (len > skb->len)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 7f4056785acc..45534a5ab430 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -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;
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 8fd9febaa5ba..8dab4e569571 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -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",
--
2.4.6
--
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