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inet: fix potential deadlock in reqsk_queue_unlink() 

When replacing del_timer() with del_timer_sync(), I introduced
a deadlock condition :

reqsk_queue_unlink() is called from inet_csk_reqsk_queue_drop()

inet_csk_reqsk_queue_drop() can be called from many contexts,
one being the timer handler itself (reqsk_timer_handler()).

In this case, del_timer_sync() loops forever.

Simple fix is to test if timer is pending.

Fixes: 2235f2ac75 ("inet: fix races with reqsk timers")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-08-13 15:44:51 -07:00 committed by David S. Miller
parent 2a4eebf0c4
commit 83fccfc394
1 changed files with 1 additions and 1 deletions
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2
net/ipv4/inet_connection_sock.c
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@ -593,7 +593,7 @@ static bool reqsk_queue_unlink(struct request_sock_queue *queue,
}
spin_unlock(&queue->syn_wait_lock);
if (del_timer_sync(&req->rsk_timer))
if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer))
reqsk_put(req);
return found;
}