netdev - Re: [PATCH] netfilter: bridge: refcount fix

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Date:	Mon, 24 Aug 2009 19:32:20 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Patrick McHardy <kaber@...sh.net>
CC:	"David S. Miller" <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Bart De Schuymer <bdschuym@...dora.be>
Subject: Re: [PATCH] netfilter: bridge: refcount fix

Patrick McHardy a écrit :
> Eric Dumazet wrote:
>> Hi David
>>
>> I found following by code review only, I am not sure it is critical enough for net-2.6
>>
>> This is a stable candidate, bug is more than 2 years old.
>>
>> Thanks
>>
>> commit f216f082b2b37c4943f1e7c393e2786648d48f6f
>> ([NETFILTER]: bridge netfilter: deal with martians correctly)
>> added a refcount leak on in_dev.
>>
>> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
>> ---
>> diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
>> index 4fde742..c62eca3 100644
>> --- a/net/bridge/br_netfilter.c
>> +++ b/net/bridge/br_netfilter.c
>> @@ -386,6 +386,7 @@ static int br_nf_pre_routing_finish(struct sk_buff *skb)
>>  				dst_release((struct dst_entry *)rt);
>>  			}
>>  free_skb:
>> +			in_dev_put(in_dev);
>>  			kfree_skb(skb);
>>  			return 0;
> 
> I guess we could simply use __in_dev_get_rcu() here since all
> netfilter hooks are running under rcu_read_lock() anyways.

Ah very good point, Thanks Patrick.

[PATCH] netfilter: bridge: refcount fix

commit f216f082b2b37c4943f1e7c393e2786648d48f6f
([NETFILTER]: bridge netfilter: deal with martians correctly)
added a refcount leak on in_dev.

Instead of using in_dev_get(), we can use __in_dev_get_rcu(),
as netfilter hooks are running under rcu_read_lock(), as pointed
by Patrick.

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Patrick McHardy <kaber@...sh.net>
---
diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index 4fde742..907a82e 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -359,7 +359,7 @@ static int br_nf_pre_routing_finish(struct sk_buff *skb)
 				},
 				.proto = 0,
 			};
-			struct in_device *in_dev = in_dev_get(dev);
+			struct in_device *in_dev = __in_dev_get_rcu(dev);
 
 			/* If err equals -EHOSTUNREACH the error is due to a
 			 * martian destination or due to the fact that
--
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