unix/dgram: fix peeking with an offset larger than data in queue
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 <bpoirier@suse.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 99c4f52..b5d48ac 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -78,9 +78,10 @@
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 @@
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 @@
* __skb_recv_datagram - Receive a datagram skbuff
* @sk: socket
* @flags: MSG_ flags
+ * @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
- * @peeked: returns non-zero if this packet has been seen before
* @err: error code returned
*
* Get a datagram skbuff, understands the peeking, nonblocking wakeups
@@ -161,7 +162,7 @@
struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
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 @@
*/
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 ||
+ if (_off >= skb->len && (skb->len || _off ||
skb->peeked)) {
- *off -= skb->len;
+ _off -= skb->len;
continue;
}
skb->peeked = 1;
@@ -198,6 +202,7 @@
__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 @@
if (!timeo)
goto no_packet;
- } while (!wait_for_packet(sk, err, &timeo));
+ } while (!wait_for_more_packets(sk, err, &timeo, last));
return NULL;