[NETFILTER]: Fix deadlock with ip_queue and tcp local input path. (9bb7bc94) · Commits · 戴 / test

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>

net/ipv4/netfilter/ip_queue.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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);
		}

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