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authorLinus Lüssing <linus.luessing@c0d3.blue>2015-08-13 05:54:07 +0200
committerDavid S. Miller <davem@davemloft.net>2015-08-13 17:08:39 -0700
commita516993f0ac1694673412eb2d16a091eafa77d2a (patch)
tree43e65ff360cc79cff96dc8c44f161fb0ad41b9c9 /net/bridge
parent5b3e2e14eaa2a98232a4f292341fb88438685734 (diff)
downloadlinux-a516993f0ac1694673412eb2d16a091eafa77d2a.tar.bz2
net: fix wrong skb_get() usage / crash in IGMP/MLD parsing code
The recent refactoring of the IGMP and MLD parsing code into ipv6_mc_check_mld() / ip_mc_check_igmp() introduced a potential crash / BUG() invocation for bridges: I wrongly assumed that skb_get() could be used as a simple reference counter for an skb which is not the case. skb_get() bears additional semantics, a user count. This leads to a BUG() invocation in pskb_expand_head() / kernel panic if pskb_may_pull() is called on an skb with a user count greater than one - unfortunately the refactoring did just that. Fixing this by removing the skb_get() call and changing the API: The caller of ipv6_mc_check_mld() / ip_mc_check_igmp() now needs to additionally check whether the returned skb_trimmed is a clone. Fixes: 9afd85c9e455 ("net: Export IGMP/MLD message validation code") Reported-by: Brenden Blanco <bblanco@plumgrid.com> Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue> Acked-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/bridge')
-rw-r--r--net/bridge/br_multicast.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 0b39dcc65b94..1285eaf5dc22 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1591,7 +1591,7 @@ static int br_multicast_ipv4_rcv(struct net_bridge *br,
break;
}
- if (skb_trimmed)
+ if (skb_trimmed && skb_trimmed != skb)
kfree_skb(skb_trimmed);
return err;
@@ -1636,7 +1636,7 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
break;
}
- if (skb_trimmed)
+ if (skb_trimmed && skb_trimmed != skb)
kfree_skb(skb_trimmed);
return err;