set fake_rtable's dst to NULL to avoid kernel Oops

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>

2 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/netfilter_bridge.h b/include/linux/netfilter_bridge.h
index 0ddd161f3b06..31d2844e6572 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 ff4da42fcfc6..bed833d9796a 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -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;