From 9bb7bc942d3da606f184ac6a4dfc7e4d470c831b Mon Sep 17 00:00:00 2001 From: Harald Welte Date: Mon, 30 May 2005 15:35:26 -0700 Subject: [PATCH] [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 Signed-off-by: David S. Miller --- net/ipv4/netfilter/ip_queue.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/net/ipv4/netfilter/ip_queue.c b/net/ipv4/netfilter/ip_queue.c index e5746b674413..eda1fba431a4 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 @@ -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 @@ -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); } -- 2.20.1