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l2tp: fix race in l2tp_recv_dequeue() 

Misha Labjuk reported panics occurring in l2tp_recv_dequeue()

If we release reorder_q.lock, we must not keep a dangling pointer (tmp),
since another thread could manipulate reorder_q.

Instead we must restart the scan at beginning of list.

Reported-by: Misha Labjuk <spiked.yar@gmail.com>
Tested-by: Misha Labjuk <spiked.yar@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2011-11-02 22:47:44 +00:00 committed by David S. Miller
parent 2edcd4ca43
commit e2e210c023
1 changed files with 2 additions and 1 deletions
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3
net/l2tp/l2tp_core.c
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@ -397,6 +397,7 @@ static void l2tp_recv_dequeue(struct l2tp_session *session)
* expect to send up next, dequeue it and any other
* in-sequence packets behind it.
*/
start:
spin_lock_bh(&session->reorder_q.lock);
skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
@ -433,7 +434,7 @@ static void l2tp_recv_dequeue(struct l2tp_session *session)
*/
spin_unlock_bh(&session->reorder_q.lock);
l2tp_recv_dequeue_skb(session, skb);
spin_lock_bh(&session->reorder_q.lock);
goto start;
}
out: