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set fake_rtable's dst to NULL to avoid kernel Oops

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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>
This commit is contained in:
Peter Huang (Peng) 2012-04-19 20:12:51 +00:00 committed by David S. Miller
parent 4d634ca35a
commit a881e963c7
4 changed files with 13 additions and 6 deletions
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9
include/linux/netfilter_bridge.h
View File

@ -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__ */

1
include/net/dst.h
View File

@ -59,6 +59,7 @@ struct dst_entry {
#define DST_NOCACHE 0x0010
#define DST_NOCOUNT 0x0020
#define DST_NOPEER 0x0040
#define DST_FAKE_RTABLE 0x0080
short error;
short obsolete;

1
net/bridge/br_forward.c
View File

@ -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);
}

8
net/bridge/br_netfilter.c
View File

@ -156,7 +156,7 @@ 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;
}
@ -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;
}