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Subject[PATCH 3.16 19/87] igmp: add a missing spin_lock_init()
3.16.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: WANG Cong <xiyou.wangcong@gmail.com>

commit b4846fc3c8559649277e3e4e6b5cec5348a8d208 upstream.

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.

Fixes: c38b7d327aaf ("igmp: acquire pmc lock for ip_mc_clear_src()")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/ipv4/igmp.c | 1 +
1 file changed, 1 insertion(+)

--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1106,6 +1106,7 @@ 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);
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