[PATCH net v2 2/3] unix/dgram: fix peeking with an offset larger than data in queue
From: Benjamin Poirier <hidden>
Date: 2013-04-26 18:36:10
Also in:
lkml
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Currently, peeking on a unix datagram socket with an offset larger than len of the data in the sk receive queue returns immediately with bogus data. That's because *off is not reset between each skb_queue_walk(). This patch fixes this so that the behavior is the same as peeking with no offset on an empty queue: the caller blocks. Signed-off-by: Benjamin Poirier <redacted> --- v2: address review feedback net/core/datagram.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-)
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 99c4f52..1985c9a 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c@@ -78,9 +78,10 @@ static int receiver_wake_function(wait_queue_t *wait, unsigned int mode, int syn return autoremove_wake_function(wait, mode, sync, key); } /* - * Wait for a packet.. + * Wait for the last received packet to be different from skb */ -static int wait_for_packet(struct sock *sk, int *err, long *timeo_p) +static int wait_for_more_packets(struct sock *sk, int *err, long *timeo_p, + const struct sk_buff *skb) { int error; DEFINE_WAIT_FUNC(wait, receiver_wake_function);
@@ -92,7 +93,7 @@ static int wait_for_packet(struct sock *sk, int *err, long *timeo_p) if (error) goto out_err; - if (!skb_queue_empty(&sk->sk_receive_queue)) + if (sk->sk_receive_queue.prev != skb) goto out; /* Socket shut down? */
@@ -131,9 +132,9 @@ out_noerr: * __skb_recv_datagram - Receive a datagram skbuff * @sk: socket * @flags: MSG_ flags - * @off: an offset in bytes to peek skb from. Returns an offset - * within an skb where data actually starts * @peeked: returns non-zero if this packet has been seen before + * @_off: an offset in bytes to peek skb from. Returns an offset + * within an skb where data actually starts * @err: error code returned * * Get a datagram skbuff, understands the peeking, nonblocking wakeups
@@ -159,9 +160,9 @@ out_noerr: * the standard around please. */ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, - int *peeked, int *off, int *err) + int *peeked, int *_off, int *err) { - struct sk_buff *skb; + struct sk_buff *skb, *last; long timeo; /* * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
@@ -182,14 +183,17 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, */ unsigned long cpu_flags; struct sk_buff_head *queue = &sk->sk_receive_queue; + int off = *_off; + last = (struct sk_buff *)queue; spin_lock_irqsave(&queue->lock, cpu_flags); skb_queue_walk(queue, skb) { + last = skb; *peeked = skb->peeked; if (flags & MSG_PEEK) { - if (*off >= skb->len && (skb->len || *off || - skb->peeked)) { - *off -= skb->len; + if (off >= skb->len && (skb->len || off || + skb->peeked)) { + off -= skb->len; continue; } skb->peeked = 1;
@@ -198,6 +202,7 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, __skb_unlink(skb, queue); spin_unlock_irqrestore(&queue->lock, cpu_flags); + *_off = off; return skb; } spin_unlock_irqrestore(&queue->lock, cpu_flags);
@@ -207,7 +212,7 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, if (!timeo) goto no_packet; - } while (!wait_for_packet(sk, err, &timeo)); + } while (!wait_for_more_packets(sk, err, &timeo, last)); return NULL;
--
1.7.10.4