ipv6: Plug sk_buff leak in ipv6_rcv (net/ipv6/ip6_input.c)

[ Upstream commit 71f6f6dfdf7c7a67462386d9ea05c1095a89c555 ]

Commit 778d80be52699596bf70e0eb0761cf5e1e46088d
(ipv6: Add disable_ipv6 sysctl to disable IPv6 operaion on specific interface)
seems to have introduced a leak of sk_buff's for ipv6 traffic,
at least in some configurations where idev is NULL, or when ipv6
is disabled via sysctl.

The problem is that if the first condition of the if-statement
returns non-NULL, it returns an skb with only one reference,
and when the other conditions apply, execution jumps to the "out"
label, which does not call kfree_skb for it.

To plug this leak, change to use the "drop" label instead.
(this relies on it being ok to call kfree_skb on NULL)
This also allows us to avoid calling rcu_read_unlock here,
and removes the only user of the "out" label.

Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 7e14ccc..e55427d 100644 (file)
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -74,8 +74,7 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
        if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
            !idev || unlikely(idev->cnf.disable_ipv6)) {
                IP6_INC_STATS_BH(idev, IPSTATS_MIB_INDISCARDS);
-               rcu_read_unlock();
-               goto out;
+               goto drop;
        }
 
        memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
@@ -145,7 +144,6 @@ err:
 drop:
        rcu_read_unlock();
        kfree_skb(skb);
-out:
        return 0;
 }