Re: [Xen-devel] [PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

[Eric Dumazet <eric.dumazet@xxxxxxxxx>]

On Mon, 2015-07-06 at 11:35 +0100, Julien Grall wrote:

> __in6_dev_get requires to hold rcu_read_lock or RTNL. My knowledge on
> this code is very limited. Are we sure that one this lock is hold? At
> first glance, I wasn't able to find one.

You could play it safe ;)

diff --git a/net/bridge/br_netfilter_ipv6.c b/net/bridge/br_netfilter_ipv6.c
index 6d12d2675c80..90e8ccc21cc5 100644
--- a/net/bridge/br_netfilter_ipv6.c
+++ b/net/bridge/br_netfilter_ipv6.c
@@ -104,10 +104,12 @@ int br_validate_ipv6(struct sk_buff *skb)
 {
        const struct ipv6hdr *hdr;
        struct net_device *dev = skb->dev;
-       struct inet6_dev *idev = in6_dev_get(skb->dev);
+       struct inet6_dev *idev;
        u32 pkt_len;
        u8 ip6h_len = sizeof(struct ipv6hdr);
 
+       rcu_read_lock();
+       idev = __in6_dev_get(dev);
        if (!pskb_may_pull(skb, ip6h_len))
                goto inhdr_error;
 
@@ -140,11 +142,13 @@ int br_validate_ipv6(struct sk_buff *skb)
        /* No IP options in IPv6 header; however it should be
         * checked if some next headers need special treatment
         */
+       rcu_read_unlock();
        return 0;
 
 inhdr_error:
        IP6_INC_STATS_BH(dev_net(dev), idev, IPSTATS_MIB_INHDRERRORS);
 drop:
+       rcu_read_unlock();
        return -1;
 }
 



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