Patch "ip6_tunnel: do not allow loading ip6_tunnel if ipv6 is disabled in cmdline" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

ip6_tunnel: do not allow loading ip6_tunnel if ipv6 is disabled in cmdline

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ip6_tunnel-do-not-allow-loading-ip6_tunnel-if-ipv6-is-disabled-in-cmdline.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Xin Long <[email protected]>
Date: Fri, 15 Sep 2017 15:58:33 +0800
Subject: ip6_tunnel: do not allow loading ip6_tunnel if ipv6 is disabled in cmdline

From: Xin Long <[email protected]>

[ Upstream commit 8c22dab03ad072e45060c299c70d02a4f6fc4aab ]

If ipv6 has been disabled from cmdline since kernel started, it makes no sense to allow users to create any ip6 tunnel. Otherwise, it could some potential problem.

Jianlin found a kernel crash caused by this in ip6_gre when he set ipv6.disable=1 in grub:

[  209.588865] Unable to handle kernel paging request for data at address 0x00000080
[  209.588872] Faulting instruction address: 0xc000000000a3aa6c
[  209.588879] Oops: Kernel access of bad area, sig: 11 [#1]
[  209.589062] NIP [c000000000a3aa6c] fib_rules_lookup+0x4c/0x260
[  209.589071] LR [c000000000b9ad90] fib6_rule_lookup+0x50/0xb0
[  209.589076] Call Trace:
[  209.589097] fib6_rule_lookup+0x50/0xb0
[  209.589106] rt6_lookup+0xc4/0x110
[  209.589116] ip6gre_tnl_link_config+0x214/0x2f0 [ip6_gre]
[  209.589125] ip6gre_newlink+0x138/0x3a0 [ip6_gre]
[  209.589134] rtnl_newlink+0x798/0xb80
[  209.589142] rtnetlink_rcv_msg+0xec/0x390
[  209.589151] netlink_rcv_skb+0x138/0x150
[  209.589159] rtnetlink_rcv+0x48/0x70
[  209.589169] netlink_unicast+0x538/0x640
[  209.589175] netlink_sendmsg+0x40c/0x480
[  209.589184] ___sys_sendmsg+0x384/0x4e0
[  209.589194] SyS_sendmsg+0xd4/0x140
[  209.589201] SyS_socketcall+0x3e0/0x4f0
[  209.589209] system_call+0x38/0xe0

This patch is to return -EOPNOTSUPP in ip6_tunnel_init if ipv6 has been disabled from cmdline.

---
 net/ipv6/ip6_tunnel.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -2258,6 +2258,9 @@ static int __init ip6_tunnel_init(void)
 {
 	int  err;
 
+	if (!ipv6_mod_enabled())
+		return -EOPNOTSUPP;
+
 	err = register_pernet_device(&ip6_tnl_net_ops);
 	if (err < 0)
 		goto out_pernet;

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/ip6_tunnel-do-not-allow-loading-ip6_tunnel-if-ipv6-is-disabled-in-cmdline.patch queue-4.13/ip6_gre-ip6gre_tap-device-should-keep-dst.patch queue-4.13/ip6_gre-skb_push-ipv6hdr-before-packing-the-header-in-ip6gre_header.patch queue-4.13/ip6_tunnel-update-mtu-properly-for-arphrd_ether-tunnel-device-in-tx-path.patch