linux-kernel - [PATCH 3.16 139/202] sit: check if IPv6 enabled before calling ip6_err_gen_icmpv6

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Message-ID: <lsq.1556377989.915778076@decadent.org.uk>
Date:   Sat, 27 Apr 2019 16:13:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Jianlin Shi" <jishi@...hat.com>,
        "Stefano Brivio" <sbrivio@...hat.com>,
        "Oussama Ghorbel" <ghorbel@...asoftware.com>,
        "Hangbin Liu" <liuhangbin@...il.com>
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@...il.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@...hat.com>
Fixes: ca15a078bd90 ("sit: generate icmpv6 error when receiving icmpv4 error")
Cc: Oussama Ghorbel <ghorbel@...asoftware.com>
Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
Reviewed-by: Stefano Brivio <sbrivio@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.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)