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Date:   Mon, 6 Mar 2017 14:25:01 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev <netdev@...r.kernel.org>
Subject: Re: [Patch net] ipv6: reorder icmpv6_init() and ip6_mr_init()

On Sun, Mar 5, 2017 at 9:34 PM, Cong Wang <xiyou.wangcong@...il.com> wrote:
> Andrey reported the following kernel crash:
>
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 0 PID: 14446 Comm: syz-executor6 Not tainted 4.10.0+ #82
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> task: ffff88001f311700 task.stack: ffff88001f6e8000
> RIP: 0010:ip6mr_sk_done+0x15a/0x3d0 net/ipv6/ip6mr.c:1618
> RSP: 0018:ffff88001f6ef418 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: 1ffff10003edde8c RCX: ffffc900043ee000
> RDX: 0000000000000004 RSI: ffffffff83e3b3f8 RDI: 0000000000000020
> RBP: ffff88001f6ef508 R08: fffffbfff0dcc5d8 R09: 0000000000000000
> R10: ffffffff86e62ec0 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: ffff88001f6ef4e0 R15: ffff8800380a0040
> FS:  00007f7a52cec700(0000) GS:ffff88003ec00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000061c500 CR3: 000000001f1ae000 CR4: 00000000000006f0
> DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
> Call Trace:
>  rawv6_close+0x4c/0x80 net/ipv6/raw.c:1217
>  inet_release+0xed/0x1c0 net/ipv4/af_inet.c:425
>  inet6_release+0x50/0x70 net/ipv6/af_inet6.c:432
>  sock_release+0x8d/0x1e0 net/socket.c:597
>  __sock_create+0x39d/0x880 net/socket.c:1226
>  sock_create_kern+0x3f/0x50 net/socket.c:1243
>  inet_ctl_sock_create+0xbb/0x280 net/ipv4/af_inet.c:1526
>  icmpv6_sk_init+0x163/0x500 net/ipv6/icmp.c:954
>  ops_init+0x10a/0x550 net/core/net_namespace.c:115
>  setup_net+0x261/0x660 net/core/net_namespace.c:291
>  copy_net_ns+0x27e/0x540 net/core/net_namespace.c:396
> 9pnet_virtio: no channels available for device ./file1
>  create_new_namespaces+0x437/0x9b0 kernel/nsproxy.c:106
>  unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
>  SYSC_unshare kernel/fork.c:2281 [inline]
>  SyS_unshare+0x64e/0x1000 kernel/fork.c:2231
>  entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> This is because net->ipv6.mr6_tables is not initialized at that point,
> ip6mr_rules_init() is not called yet, therefore on the error path when
> we iterator the list, we trigger this oops. Fix this by reordering
> ip6mr_rules_init() before icmpv6_sk_init().
>
> Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> ---
>  net/ipv6/af_inet6.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
> index 04db406..a9a9553 100644
> --- a/net/ipv6/af_inet6.c
> +++ b/net/ipv6/af_inet6.c
> @@ -920,12 +920,12 @@ static int __init inet6_init(void)
>         err = register_pernet_subsys(&inet6_net_ops);
>         if (err)
>                 goto register_pernet_fail;
> -       err = icmpv6_init();
> -       if (err)
> -               goto icmp_fail;
>         err = ip6_mr_init();
>         if (err)
>                 goto ipmr_fail;
> +       err = icmpv6_init();
> +       if (err)
> +               goto icmp_fail;
>         err = ndisc_init();
>         if (err)
>                 goto ndisc_fail;
> @@ -1061,10 +1061,10 @@ static int __init inet6_init(void)
>         ndisc_cleanup();
>  ndisc_fail:
>         ip6_mr_cleanup();
> -ipmr_fail:
> -       icmpv6_cleanup();
>  icmp_fail:
>         unregister_pernet_subsys(&inet6_net_ops);
> +ipmr_fail:
> +       icmpv6_cleanup();
>  register_pernet_fail:
>         sock_unregister(PF_INET6);
>         rtnl_unregister_all(PF_INET6);
> --
> 2.5.5
>

Thanks!

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