From: Harald Welte Date: Mon, 30 May 2005 22:38:14 +0000 (-0700) Subject: [PATCH] Fix deadlock with ip_queue and tcp local input path. X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=839c2379a6ed8ea9dd669d4c3206b85c5dff674e;p=thirdparty%2Fkernel%2Fstable.git [PATCH] 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 Signed-off-by: David S. Miller Signed-off-by: Chris Wright Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/ipv4/netfilter/ip_queue.c b/net/ipv4/netfilter/ip_queue.c index a9aa12cc83bb4..470a9055488eb 100644 --- a/net/ipv4/netfilter/ip_queue.c +++ b/net/ipv4/netfilter/ip_queue.c @@ -3,6 +3,7 @@ * communicating with userspace via netlink. * * (C) 2000-2002 James Morris + * (C) 2003-2005 Netfilter Core Team * * 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 @@ -14,6 +15,7 @@ * Zander). * 2000-08-01: Added Nick Williams' MAC support. * 2002-06-25: Code cleanup. + * 2005-05-26: local_bh_{disable,enable} around nf_reinject (Harald Welte) * */ #include @@ -66,7 +68,15 @@ 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); }