netdev - [PATCH net 1/3] ipv6: fix cleanup ordering for ip6

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Date:   Tue, 28 Aug 2018 13:40:51 +0200
From:   Sabrina Dubroca <sd@...asysnail.net>
To:     netdev@...r.kernel.org
Cc:     Sabrina Dubroca <sd@...asysnail.net>,
        WANG Cong <xiyou.wangcong@...il.com>,
        Xin Long <lxin@...hat.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH net 1/3] ipv6: fix cleanup ordering for ip6_mr failure

Commit 15e668070a64 ("ipv6: reorder icmpv6_init() and ip6_mr_init()")
moved the cleanup label for ipmr_fail, but should have changed the
contents of the cleanup labels as well. Now we can end up cleaning up
icmpv6 even though it hasn't been initialized (jump to icmp_fail or
ipmr_fail).

Simply undo things in the reverse order of their initialization.

Example of panic (triggered by faking a failure of icmpv6_init):

    kasan: GPF could be caused by NULL-ptr deref or user memory access
    general protection fault: 0000 [#1] PREEMPT SMP KASAN PTI
    [...]
    RIP: 0010:__list_del_entry_valid+0x79/0x160
    [...]
    Call Trace:
     ? lock_release+0x8a0/0x8a0
     unregister_pernet_operations+0xd4/0x560
     ? ops_free_list+0x480/0x480
     ? down_write+0x91/0x130
     ? unregister_pernet_subsys+0x15/0x30
     ? down_read+0x1b0/0x1b0
     ? up_read+0x110/0x110
     ? kmem_cache_create_usercopy+0x1b4/0x240
     unregister_pernet_subsys+0x1d/0x30
     icmpv6_cleanup+0x1d/0x30
     inet6_init+0x1b5/0x23f

Fixes: 15e668070a64 ("ipv6: reorder icmpv6_init() and ip6_mr_init()")
Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
 net/ipv6/af_inet6.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 673bba31eb18..e5da133c6932 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -1113,11 +1113,11 @@ static int __init inet6_init(void)
 igmp_fail:
 	ndisc_cleanup();
 ndisc_fail:
-	ip6_mr_cleanup();
+	icmpv6_cleanup();
 icmp_fail:
-	unregister_pernet_subsys(&inet6_net_ops);
+	ip6_mr_cleanup();
 ipmr_fail:
-	icmpv6_cleanup();
+	unregister_pernet_subsys(&inet6_net_ops);
 register_pernet_fail:
 	sock_unregister(PF_INET6);
 	rtnl_unregister_all(PF_INET6);
-- 
2.18.0