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inet: fix potential deadlock in reqsk_queue_unlink()
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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: 2235f2a ("inet: fix races with reqsk timers")
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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Eric Dumazet authored and davem330 committed Aug 14, 2015
1 parent 2a4eebf commit 83fccfc
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion net/ipv4/inet_connection_sock.c
Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
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