[PATCH net] ipv6: Fix mem leak in rt6i_pcpu

[PATCH net] ipv6: Fix mem leak in rt6i_pcpu

[Martin KaFai Lau]

It was first reported and reproduced by Petr (thanks!) in
https://bugzilla.kernel.org/show_bug.cgi?id=119581

free_percpu(rt->rt6i_pcpu) used to always happen in ip6_dst_destroy().

However, after fixing a deadlock bug in
commit 9c7370a166b4 ("ipv6: Fix a potential deadlock when creating pcpu rt"),
free_percpu() is not called before setting non_pcpu_rt->rt6i_pcpu to NULL.

It is worth to note that rt6i_pcpu is protected by table->tb6_lock.

kmemleak somehow did not report it.  We nailed it down by
observing the pcpu entries in /proc/vmallocinfo (first suggested
by Hannes, thanks!).

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Fixes: 9c7370a166b4 ("ipv6: Fix a potential deadlock when creating pcpu rt")
Reported-by: Petr Novopashenniy <pety@rusnet.ru>
Tested-by: Petr Novopashenniy <pety@rusnet.ru>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Petr Novopashenniy <pety@rusnet.ru>
---
 net/ipv6/ip6_fib.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 1bcef23..771be1f 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -177,6 +177,7 @@ static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)
 		}
 	}
 
+	free_percpu(non_pcpu_rt->rt6i_pcpu);
 	non_pcpu_rt->rt6i_pcpu = NULL;
 }
 
-- 
2.5.1

Re: [PATCH net] ipv6: Fix mem leak in rt6i_pcpu

[David Miller]

From: Martin KaFai Lau <kafai@fb.com>
Date: Tue, 5 Jul 2016 12:10:23 -0700

> It was first reported and reproduced by Petr (thanks!) in
> https://bugzilla.kernel.org/show_bug.cgi?id=119581
> 
> free_percpu(rt->rt6i_pcpu) used to always happen in ip6_dst_destroy().
> 
> However, after fixing a deadlock bug in
> commit 9c7370a166b4 ("ipv6: Fix a potential deadlock when creating pcpu rt"),
> free_percpu() is not called before setting non_pcpu_rt->rt6i_pcpu to NULL.
> 
> It is worth to note that rt6i_pcpu is protected by table->tb6_lock.
> 
> kmemleak somehow did not report it.  We nailed it down by
> observing the pcpu entries in /proc/vmallocinfo (first suggested
> by Hannes, thanks!).
> 
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> Fixes: 9c7370a166b4 ("ipv6: Fix a potential deadlock when creating pcpu rt")
> Reported-by: Petr Novopashenniy <pety@rusnet.ru>
> Tested-by: Petr Novopashenniy <pety@rusnet.ru>
> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Cc: Petr Novopashenniy <pety@rusnet.ru>

Applied and queued up for -stable.