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    Subject[ 65/82] set fake_rtables dst to NULL to avoid kernel Oops
    3.2-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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;
    }




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