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Subject[PATCH 3.16 139/202] sit: check if IPv6 enabled before calling ip6_err_gen_icmpv6_unreach()
3.16.66-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Hangbin Liu <liuhangbin@gmail.com>

commit 173656accaf583698bac3f9e269884ba60d51ef4 upstream.

If we disabled IPv6 from the kernel command line (ipv6.disable=1), we should
not call ip6_err_gen_icmpv6_unreach(). This:

ip link add sit1 type sit local 192.0.2.1 remote 192.0.2.2 ttl 1
ip link set sit1 up
ip addr add 198.51.100.1/24 dev sit1
ping 198.51.100.2

if IPv6 is disabled at boot time, will crash the kernel.

v2: there's no need to use in6_dev_get(), use __in6_dev_get() instead,
as we only need to check that idev exists and we are under
rcu_read_lock() (from netif_receive_skb_internal()).

Reported-by: Jianlin Shi <jishi@redhat.com>
Fixes: ca15a078bd90 ("sit: generate icmpv6 error when receiving icmpv4 error")
Cc: Oussama Ghorbel <ghorbel@pivasoftware.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/ipv6/sit.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -576,7 +576,8 @@ static int ipip6_err(struct sk_buff *skb
goto out;

err = 0;
- if (!ipip6_err_gen_icmpv6_unreach(skb))
+ if (__in6_dev_get(skb->dev) &&
+ !ipip6_err_gen_icmpv6_unreach(skb))
goto out;

if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
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