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unix/dgram: peek beyond 0-sized skbs

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"77c1090 net: fix infinite loop in __skb_recv_datagram()" (v3.8) introduced a
regression:
After that commit, recv can no longer peek beyond a 0-sized skb in the queue.
__skb_recv_datagram() instead stops at the first skb with len == 0 and results
in the system call failing with -EFAULT via skb_copy_datagram_iovec().

When peeking at an offset with 0-sized skb(s), each one of those is received
only once, in sequence. The offset starts moving forward again after receiving
datagrams with len > 0.

Signed-off-by: Benjamin Poirier <bpoirier@suse.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Benjamin Poirier 2013-04-29 11:42:12 +00:00 committed by David S. Miller
parent e5195c1f31
commit add05ad4e9
1 changed files with 2 additions and 1 deletions
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3
net/core/datagram.c
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@ -187,7 +187,8 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
skb_queue_walk(queue, skb) {
*peeked = skb->peeked;
if (flags & MSG_PEEK) {
if (*off >= skb->len && skb->len) {
if (*off >= skb->len && (skb->len || *off ||
skb->peeked)) {
*off -= skb->len;
continue;
}