[ 65/82] set fake_rtables dst to NULL to avoid kernel Oops

Ben Hutchings
2012-06-08T05:09:34Z

From: "Peter Huang (Peng)" <peter.huangpeng@huawei.com>

[ Upstream commit a881e963c7fe1f226e991ee9bbe8907acda93294 ]

bridge: set fake_rtable's dst to NULL to avoid kernel Oops

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.

v4 reformat, change br_drop_fake_rtable(skb) to {}

v3 enrich commit header

v2 introducing new flag DST_FAKE_RTABLE to dst_entry struct.

[ Use "do { } while (0)" for nop br_drop_fake_rtable()
implementation -DaveM ]

Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Peter Huang <peter.huangpeng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
include/linux/netfilter_bridge.h | 9 +++++++++
include/net/dst.h | 1 +
net/bridge/br_forward.c | 1 +
net/bridge/br_netfilter.c | 8 ++------
4 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/linux/netfilter_bridge.h b/include/linux/netfilter_bridge.h
index 0ddd161..31d2844 100644
--- a/include/linux/netfilter_bridge.h
+++ b/include/linux/netfilter_bridge.h
@@ -104,9 +104,18 @@ struct bridge_skb_cb {
} daddr;
};

+static inline void br_drop_fake_rtable(struct sk_buff *skb)
+{
+ struct dst_entry *dst = skb_dst(skb);
+
+ if (dst && (dst->flags & DST_FAKE_RTABLE))
+ 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) do { } while (0)
#endif /* CONFIG_BRIDGE_NETFILTER */

#endif /* __KERNEL__ */
diff --git a/include/net/dst.h b/include/net/dst.h
index 75766b4..65bca65 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -54,6 +54,7 @@ struct dst_entry {
#define DST_NOCACHE 0x0010
#define DST_NOCOUNT 0x0020
#define DST_NOPEER 0x0040
+#define DST_FAKE_RTABLE 0x0080

short error;
short obsolete;
diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index ee64287..e221f88 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 fa8b8f7..577ea5d 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -147,7 +147,7 @@ void br_netfilter_rtable_init(struct net_bridge *br)
rt->dst.dev = br->dev;
rt->dst.path = &rt->dst;
dst_init_metrics(&rt->dst, br_dst_default_metrics, true);
- rt->dst.flags = DST_NOXFRM | DST_NOPEER;
+ rt->dst.flags = DST_NOXFRM | DST_NOPEER | DST_FAKE_RTABLE;
rt->dst.ops = &fake_dst_ops;
}

@@ -687,11 +687,7 @@ 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;
}