[NETFILTER]: Fix deadlock with ip_queue and tcp local input path.

When we have ip_queue being used from LOCAL_IN, then we end up with a
situation where the verdicts coming back from userspace traverse the TCP
input path from syscall context.  While this seems to work most of the
time, there's an ugly deadlock:

syscall context is interrupted by the timer interrupt.  When the timer
interrupt leaves, the timer softirq get's scheduled and calls
tcp_delack_timer() and alike.  They themselves do bh_lock_sock(sk),
which is already held from somewhere else -> boom.

I've now tested the suggested solution by Patrick McHardy and Herbert Xu to
simply use local_bh_{en,dis}able().

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Harald Welte 2005-05-30 15:35:26 -07:00 committed by David S. Miller
parent 5e485b7975
commit 9bb7bc942d
1 changed files with 10 additions and 0 deletions

View File

@ -3,6 +3,7 @@
* communicating with userspace via netlink.
*
* (C) 2000-2002 James Morris <jmorris@intercode.com.au>
* (C) 2003-2005 Netfilter Core Team <coreteam@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
@ -17,6 +18,7 @@
* 2005-01-10: Added /proc counter for dropped packets; fixed so
* packets aren't delivered to user space if they're going
* to be dropped.
* 2005-05-26: local_bh_{disable,enable} around nf_reinject (Harald Welte)
*
*/
#include <linux/module.h>
@ -71,7 +73,15 @@ static DECLARE_MUTEX(ipqnl_sem);
static void
ipq_issue_verdict(struct ipq_queue_entry *entry, int verdict)
{
/* TCP input path (and probably other bits) assume to be called
* from softirq context, not from syscall, like ipq_issue_verdict is
* called. TCP input path deadlocks with locks taken from timer
* softirq, e.g. We therefore emulate this by local_bh_disable() */
local_bh_disable();
nf_reinject(entry->skb, entry->info, verdict);
local_bh_enable();
kfree(entry);
}