Patch "igmp: add a missing spin_lock_init()" has been added to the 4.9-stable tree

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

igmp: add a missing spin_lock_init()

to the 4.9-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:
igmp-add-a-missing-spin_lock_init.patch
and it can be found in the queue-4.9 subdirectory.

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

From: WANG Cong <[email protected]>
Date: Tue, 20 Jun 2017 10:46:27 -0700
Subject: igmp: add a missing spin_lock_init()

From: WANG Cong <[email protected]>

[ Upstream commit b4846fc3c8559649277e3e4e6b5cec5348a8d208 ]

Andrey reported a lockdep warning on non-initialized spinlock:

INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.

 CPU: 1 PID: 4099 Comm: a.out Not tainted 4.12.0-rc6+ #9
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 Call Trace:
  __dump_stack lib/dump_stack.c:16
  dump_stack+0x292/0x395 lib/dump_stack.c:52
  register_lock_class+0x717/0x1aa0 kernel/locking/lockdep.c:755
  ? 0xffffffffa0000000
  __lock_acquire+0x269/0x3690 kernel/locking/lockdep.c:3255
  lock_acquire+0x22d/0x560 kernel/locking/lockdep.c:3855
  __raw_spin_lock_bh ./include/linux/spinlock_api_smp.h:135
  _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:175
  spin_lock_bh ./include/linux/spinlock.h:304
  ip_mc_clear_src+0x27/0x1e0 net/ipv4/igmp.c:2076
  igmpv3_clear_delrec+0xee/0x4f0 net/ipv4/igmp.c:1194
  ip_mc_destroy_dev+0x4e/0x190 net/ipv4/igmp.c:1736

We miss a spin_lock_init() in igmpv3_add_delrec(), probably because previously we never use it on this code path. Since we already unlink it from the global mc_tomb list, it is probably safe not to acquire this spinlock here. It does not harm to have it although, to avoid conditional locking.

---
 net/ipv4/igmp.c |    1 +
 1 file changed, 1 insertion(+)

@@ -1112,6 +1112,7 @@ static void igmpv3_add_delrec(struct in_
 	pmc = kzalloc(sizeof(*pmc), GFP_KERNEL);
 	if (!pmc)
 		return;
+	spin_lock_init(&pmc->lock);
 	spin_lock_bh(&im->lock);
 	pmc->interface = im->interface;
 	in_dev_hold(in_dev);

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

queue-4.9/igmp-add-a-missing-spin_lock_init.patch queue-4.9/igmp-acquire-pmc-lock-for-ip_mc_clear_src.patch