Re: [PATCH net] ip6_tunnel: do not allow loading ip6_tunnel if ipv6 is disabled in cmdline

[David Miller]

From: Xin Long 
Date: Fri, 15 Sep 2017 15:58:33 +0800

> 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 
> 0x0080
> [  209.588872] Faulting instruction address: 0xc0a3aa6c
> [  209.588879] Oops: Kernel access of bad area, sig: 11 [#1]
> [  209.589062] NIP [c0a3aa6c] fib_rules_lookup+0x4c/0x260
> [  209.589071] LR [c0b9ad90] 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 
> Signed-off-by: Xin Long 

Applied and queued up for -stable, thanks.

[PATCH net] ip6_tunnel: do not allow loading ip6_tunnel if ipv6 is disabled in cmdline

[Xin Long]

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 
0x0080
[  209.588872] Faulting instruction address: 0xc0a3aa6c
[  209.588879] Oops: Kernel access of bad area, sig: 11 [#1]
[  209.589062] NIP [c0a3aa6c] fib_rules_lookup+0x4c/0x260
[  209.589071] LR [c0b9ad90] 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 
Signed-off-by: Xin Long 
---
 net/ipv6/ip6_tunnel.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index ae73164..f2f21c2 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -2259,6 +2259,9 @@ static int __init ip6_tunnel_init(void)
 {
int  err;
 
+   if (!ipv6_mod_enabled())
+   return -EOPNOTSUPP;
+
err = register_pernet_device(_tnl_net_ops);
if (err < 0)
goto out_pernet;
-- 
2.1.0