[PATCH] set fake_rtable's dst to NULL to avoid kernel Oops.

Peter Huang (Peng)
2012-04-17T06:22:26Z

When bridge is deleted before tap/vif device's delete, kernel may encounter an oops because of NULL reference to fake_rtable's dst.
Set fake_rtable's dst to NULL before sending packets out can solve this problem.

Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Peter Huang <peter.huangpeng@huawei.com>
---
include/linux/netfilter_bridge.h | 8 ++++++++
net/bridge/br_forward.c | 1 +
net/bridge/br_netfilter.c | 6 +-----
3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/include/linux/netfilter_bridge.h b/include/linux/netfilter_bridge.h
index 0ddd161..70744fe 100644
--- a/include/linux/netfilter_bridge.h
+++ b/include/linux/netfilter_bridge.h
@@ -104,9 +104,17 @@ struct bridge_skb_cb {
} daddr;
};

+static inline void br_drop_fake_rtable(struct sk_buff *skb) {
+ struct dst_entry *dst = skb_dst(skb);
+ /* abuse fact that only fake_rtable has DST_NOPEER set */
+ if (dst && (dst->flags & DST_NOPEER))
+ skb_dst_drop(skb);
+}
+
#else
#define nf_bridge_maybe_copy_header(skb) (0)
#define nf_bridge_pad(skb) (0)
+#define br_drop_fake_rtable(skb) (0)
#endif /* CONFIG_BRIDGE_NETFILTER */

#endif /* __KERNEL__ */
diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c index 61f6534..a2098e3 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -47,6 +47,7 @@ int br_dev_queue_push_xmit(struct sk_buff *skb)
kfree_skb(skb);
} else {
skb_push(skb, ETH_HLEN);
+ br_drop_fake_rtable(skb);
dev_queue_xmit(skb);
}

diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c index dec4f38..946dcb0 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -694,11 +694,7 @@ static unsigned int br_nf_local_in(unsigned int hook, struct sk_buff *skb,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
- struct rtable *rt = skb_rtable(skb);
-
- if (rt && rt == bridge_parent_rtable(in))
- skb_dst_drop(skb);
-
+ br_drop_fake_rtable(skb);
return NF_ACCEPT;
}
--------------------------------
Peter Huang(peng)