Patch "ipv6: fix possible deadlock in ip6_fl_purge / ip6_fl_gc" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

ipv6: fix possible deadlock in ip6_fl_purge / ip6_fl_gc

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ipv6-fix-possible-deadlock-in-ip6_fl_purge-ip6_fl_gc.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jan Stancek <[email protected]>
Date: Wed, 11 Feb 2015 14:06:23 +0100
Subject: ipv6: fix possible deadlock in ip6_fl_purge / ip6_fl_gc

From: Jan Stancek <[email protected]>

commit 4762fb980465463734f02c67c67f40beb8903f73 upstream.

Use spin_lock_bh in ip6_fl_purge() to prevent following potentially deadlock scenario between ip6_fl_purge() and ip6_fl_gc() timer.

=================================
[ INFO: inconsistent lock state ]
3.19.0 #1 Not tainted
---------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. swapper/5/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
(ip6_fl_lock){+.?...}, at: [<ffffffff8171155d>] ip6_fl_gc+0x2d/0x180
{SOFTIRQ-ON-W} state was registered at:

    [<ffffffff810ee9a0>] __lock_acquire+0x4a0/0x10b0
    [<ffffffff810efd54>] lock_acquire+0xc4/0x2b0
    [<ffffffff81751d2d>] _raw_spin_lock+0x3d/0x80
    [<ffffffff81711798>] ip6_flowlabel_net_exit+0x28/0x110
    [<ffffffff815f9759>] ops_exit_list.isra.1+0x39/0x60
    [<ffffffff815fa320>] cleanup_net+0x100/0x1e0
    [<ffffffff810ad80a>] process_one_work+0x20a/0x830
    [<ffffffff810adf4b>] worker_thread+0x11b/0x460
    [<ffffffff810b42f4>] kthread+0x104/0x120
    [<ffffffff81752bfc>] ret_from_fork+0x7c/0xb0
  irq event stamp: 84640
  hardirqs last  enabled at (84640): [<ffffffff81752080>] _raw_spin_unlock_irq+0x30/0x50
  hardirqs last disabled at (84639): [<ffffffff81751eff>] _raw_spin_lock_irq+0x1f/0x80
  softirqs last  enabled at (84628): [<ffffffff81091ad1>] _local_bh_enable+0x21/0x50
  softirqs last disabled at (84629): [<ffffffff81093b7d>] irq_exit+0x12d/0x150

other info that might help us debug this:

   Possible unsafe locking scenario:

         CPU0
         ----
    lock(ip6_fl_lock);
    <Interrupt>
      lock(ip6_fl_lock);

*** DEADLOCK ***

---
 net/ipv6/ip6_flowlabel.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -172,7 +172,7 @@ static void __net_exit ip6_fl_purge(stru
 {
 	int i;
 
-	spin_lock(&ip6_fl_lock);
+	spin_lock_bh(&ip6_fl_lock);
 	for (i = 0; i <= FL_HASH_MASK; i++) {
 		struct ip6_flowlabel *fl;
 		struct ip6_flowlabel __rcu **flp;

@@ -190,7 +190,7 @@ static void __net_exit ip6_fl_purge(stru
 			flp = &fl->next;
 		}
 	}
-	spin_unlock(&ip6_fl_lock);
+	spin_unlock_bh(&ip6_fl_lock);
 }
 
 static struct ip6_flowlabel *fl_intern(struct net *net,

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/ipv6-fix-possible-deadlock-in-ip6_fl_purge-ip6_fl_gc.patch