Patchwork BUG: unable to handle kernel NULL pointer dereference at br_multicast_leave_group

login
register
mail settings
Submitter Herbert Xu
Date March 16, 2010, 3:10 a.m.
Message ID <20100316031005.GA17727@gondor.apana.org.au>
Download mbox | patch
Permalink /patch/47803/
State Accepted
Delegated to: David Miller
Headers show

Comments

Herbert Xu - March 16, 2010, 3:10 a.m.
michael-dev@fami-braun.de wrote:
> 
> I'm currently using linux-next and have been running into an OOPs which
> I think might be caused by a patch you submitted on 2010-02-27.
> 
> It's a linux-next kernel from 2010-03-12 on an x86 system and it
> OOPs in the bridge module in br_mdp_ip_get (called by
> br_multicast_leave_group) because the br->mdb is null.

Thanks, there's actually another spot (the query handler) where
the same thing can happen.

Here's a patch to fix them both.

bridge: Move NULL mdb check into br_mdb_ip_get

Since all callers of br_mdb_ip_get need to check whether the
hash table is NULL, this patch moves the check into the function.

This fixes the two callers (query/leave handler) that didn't
check it.

Reported-by: Michael Braun <michael-dev@fami-braun.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>


Thanks,
David Miller - March 16, 2010, 3:38 a.m.
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Tue, 16 Mar 2010 11:10:05 +0800

> michael-dev@fami-braun.de wrote:
>> 
>> I'm currently using linux-next and have been running into an OOPs which
>> I think might be caused by a patch you submitted on 2010-02-27.
>> 
>> It's a linux-next kernel from 2010-03-12 on an x86 system and it
>> OOPs in the bridge module in br_mdp_ip_get (called by
>> br_multicast_leave_group) because the br->mdb is null.
> 
> Thanks, there's actually another spot (the query handler) where
> the same thing can happen.
> 
> Here's a patch to fix them both.
> 
> bridge: Move NULL mdb check into br_mdb_ip_get
> 
> Since all callers of br_mdb_ip_get need to check whether the
> hash table is NULL, this patch moves the check into the function.
> 
> This fixes the two callers (query/leave handler) that didn't
> check it.
> 
> Reported-by: Michael Braun <michael-dev@fami-braun.de>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Applied, thanks Herbert.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index fd96a8d..398221e 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -49,22 +49,23 @@  static struct net_bridge_mdb_entry *__br_mdb_ip_get(
 static struct net_bridge_mdb_entry *br_mdb_ip_get(
 	struct net_bridge_mdb_htable *mdb, __be32 dst)
 {
+	if (!mdb)
+		return NULL;
+
 	return __br_mdb_ip_get(mdb, dst, br_ip_hash(mdb, dst));
 }
 
 struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
 					struct sk_buff *skb)
 {
-	struct net_bridge_mdb_htable *mdb = br->mdb;
-
-	if (!mdb || br->multicast_disabled)
+	if (br->multicast_disabled)
 		return NULL;
 
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
 		if (BR_INPUT_SKB_CB(skb)->igmp)
 			break;
-		return br_mdb_ip_get(mdb, ip_hdr(skb)->daddr);
+		return br_mdb_ip_get(br->mdb, ip_hdr(skb)->daddr);
 	}
 
 	return NULL;