[SRU][Vivid][PATCH v2 4/4] netfilter: bridge: Use __in6_dev_get rather than in6_dev_get in br_validate_ipv6

[Jay Vosburgh]

From: Julien Grall <julien.grall at citrix.com>

BugLink: https://bugs.launchpad.net/nova/+bug/1463911

The commit efb6de9b4ba0092b2c55f6a52d16294a8a698edd "netfilter: bridge:
forward IPv6 fragmented packets" introduced a new function
br_validate_ipv6 which take a reference on the inet6 device. Although,
the reference is not released at the end.

This will result to the impossibility to destroy any netdevice using
ipv6 and bridge.

It's possible to directly retrieve the inet6 device without taking a
reference as all netfilter hooks are protected by rcu_read_lock via
nf_hook_slow.

Spotted while trying to destroy a Xen guest on the upstream Linux:
"unregister_netdevice: waiting for vif1.0 to become free. Usage count = 1"

Signed-off-by: Julien Grall <julien.grall at citrix.com>
Cc: Bernhard Thaler <bernhard.thaler at wvnet.at>
Cc: Pablo Neira Ayuso <pablo at netfilter.org>
Cc: fw at strlen.de
Cc: ian.campbell at citrix.com
Cc: wei.liu2 at citrix.com
Cc: Bob Liu <bob.liu at oracle.com>
Acked-by: Stephen Hemminger <stephen at networkplumber.org>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
(backported from commit 86e8971800381c3a8d8d9327f83b1f97ccb04a4f)
Signed-off-by: Jay Vosburgh <jay.vosburgh at canonical.com>
---
 net/bridge/br_netfilter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index 9249c7ef3604..7cd1e1228ab7 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -546,7 +546,7 @@ static 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 = __in6_dev_get(skb->dev);
 	u32 pkt_len;
 	u8 ip6h_len = sizeof(struct ipv6hdr);
 
-- 
1.9.1