From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net] ip6_tunnel: do not allow loading ip6_tunnel if
 ipv6 is disabled in cmdline
Date: Mon, 18 Sep 2017 16:35:14 -0700 (PDT)
Message-ID: <20170918.163514.1255529758008159884.davem@davemloft.net>
References: <107ac334855fea1e6492b2e523b788209e54ec2f.1505462312.git.lucien.xin@gmail.com>
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Cc: netdev@vger.kernel.org, xeb@mail.ru, jbenc@redhat.com
To: lucien.xin@gmail.com
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From: Xin Long <lucien.xin@gmail.com>
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 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>

Applied and queued up for -stable, thanks.