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inet: fix races with reqsk timers

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reqsk_queue_destroy() and reqsk_queue_unlink() should use
del_timer_sync() instead of del_timer() before calling reqsk_put(),
otherwise we could free a req still used by another cpu.

But before doing so, reqsk_queue_destroy() must release syn_wait_lock
spinlock or risk a dead lock, as reqsk_timer_handler() might
need to take this same spinlock from reqsk_queue_unlink() (called from
inet_csk_reqsk_queue_drop())

Fixes: fa76ce7328 ("inet: get rid of central tcp/dccp listener timer")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-08-10 09:09:13 -07:00 committed by David S. Miller
parent 9d332d92a9
commit 2235f2ac75
2 changed files with 8 additions and 2 deletions
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8
net/core/request_sock.c
View File

@ -103,10 +103,16 @@ void reqsk_queue_destroy(struct request_sock_queue *queue)
spin_lock_bh(&queue->syn_wait_lock);
while ((req = lopt->syn_table[i]) != NULL) {
lopt->syn_table[i] = req->dl_next;
/* Because of following del_timer_sync(),
* we must release the spinlock here
* or risk a dead lock.
*/
spin_unlock_bh(&queue->syn_wait_lock);
atomic_inc(&lopt->qlen_dec);
if (del_timer(&req->rsk_timer))
if (del_timer_sync(&req->rsk_timer))
reqsk_put(req);
reqsk_put(req);
spin_lock_bh(&queue->syn_wait_lock);
}
spin_unlock_bh(&queue->syn_wait_lock);
}

2
net/ipv4/inet_connection_sock.c
View File

@ -593,7 +593,7 @@ static bool reqsk_queue_unlink(struct request_sock_queue *queue,
}
spin_unlock(&queue->syn_wait_lock);
if (del_timer(&req->rsk_timer))
if (del_timer_sync(&req->rsk_timer))
reqsk_put(req);
return found;
}