ip6_tunnel: do not allow loading ip6_tunnel if ipv6 is disabled in cmdline
authorXin Long <lucien.xin@gmail.com>
Fri, 15 Sep 2017 07:58:33 +0000 (15:58 +0800)
committerDavid S. Miller <davem@davemloft.net>
Mon, 18 Sep 2017 23:34:32 +0000 (16:34 -0700)
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.

Reported-by: Jianlin Shi <jishi@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv6/ip6_tunnel.c

index ae73164559d5c4d7f2650ae63c56d76dc93b165c..f2f21c24915f1079939dc2b88546aa0185010239 100644 (file)
@@ -2259,6 +2259,9 @@ 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;