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From: Andrey Konovalov <andreyknvl@google.com>
Date: Thu, 3 Nov 2016 16:49:15 +0100
Message-ID: <CAAeHK+wZtjegrMcEqphEs3MJ5kckf=zDSfE1pd3aNjs_NKyHdw@mail.gmail.com>
Subject: Re: net/ipv6: null-ptr-deref in inet6_bind
To: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        James Morris <jmorris@namei.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Patrick McHardy <kaber@trash.net>, netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Alexander Potapenko <glider@google.com>,
        Kostya Serebryany <kcc@google.com>,
        syzkaller <syzkaller@googlegroups.com>
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Hi Eric,

It seems that your patch fixes the issue, I'm not seeing the report any more.

Tested-by: Andrey Konovalov <andreyknvl@google.com>

Thanks!

On Thu, Nov 3, 2016 at 4:39 PM, Eric Dumazet <edumazet@google.com> wrote:
> On Wed, Nov 2, 2016 at 2:14 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>> Hi,
>>
>> I've got the following error report while running the syzkaller fuzzer:
>>
>> BUG: unable to handle kernel NULL pointer dereference at           (null)
>> IP: [<          (null)>]           (null)
>> PGD 66b6f067 [  102.549865] PUD 66c6e067
>> PMD 0 [  102.549865]
>> Oops: 0010 [#1] SMP KASAN
>> Modules linked in:
>> CPU: 0 PID: 4143 Comm: a.out Not tainted 4.9.0-rc3+ #336
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> task: ffff880066b1c200 task.stack: ffff880065b58000
>> RIP: 0010:[<0000000000000000>]  [<          (null)>]           (null)
>> RSP: 0018:ffff880065b5fbc0  EFLAGS: 00010246
>> RAX: ffff880066b1c200 RBX: ffff88006873864a RCX: 0000000000000000
>> RDX: 0000000000000001 RSI: ffff880068738640 RDI: ffff880063bd3200
>> RBP: ffff880065b5fd20 R08: 1ffff1000c77a713 R09: dffffc0000000000
>> R10: ffffffff844fc800 R11: 1ffff1000d0e70c9 R12: ffffffff84e7e040
>> R13: ffff880068738640 R14: ffff880063bd3200 R15: ffffffff86836380
>> FS:  00007f40b7acf700(0000) GS:ffff88006cc00000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000000000000000 CR3: 000000006bb28000 CR4: 00000000000006f0
>> Stack:
>>  ffffffff83099988 ffffffff8479f7e8 ffffffff81208580 1ffff1000000000c
>>  0000000041b58ab3 ffffffff8479f7e8 ffffffff81208580 ffffffff812506ed
>>  0000000000000007 ffff880065b5fc18 ffffffff812506ed ffff880065b5fcd0
>> Call Trace:
>>  [<ffffffff832cf4fc>] inet6_bind+0x8ec/0x1020 net/ipv6/af_inet6.c:384
>>  [<ffffffff82b7033c>] SYSC_bind+0x1ec/0x250 net/socket.c:1367
>>  [<ffffffff82b72ae4>] SyS_bind+0x24/0x30 net/socket.c:1353
>>  [<ffffffff83fc0401>] entry_SYSCALL_64_fastpath+0x1f/0xc2
>> arch/x86/entry/entry_64.S:209
>> Code:  Bad RIP value.
>> RIP  [<          (null)>]           (null)
>>  RSP <ffff880065b5fbc0>
>> CR2: 0000000000000000
>> ---[ end trace b5ec698ae4926a97 ]---
>> Kernel panic - not syncing: Fatal exception in interrupt
>> Kernel Offset: disabled
>> ---[ end Kernel panic - not syncing: Fatal exception in interrupt
>>
>> On commit 0c183d92b20b5c84ca655b45ef57b3318b83eb9e (Oct 31).
>>
>> I'm able to reproduce it with the attached program by running it as:
>> $ gcc -lpthread inet6-bind-poc.c
>> $ while true; do ./a.out; done
>>
>> Thanks!
>
> Looks like this patch should fix it ?
>
> Thanks !
>
> diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
> index 3828f94b234c..95353bdbfa7b 100644
> --- a/net/dccp/ipv6.c
> +++ b/net/dccp/ipv6.c
> @@ -956,6 +956,7 @@ static const struct inet_connection_sock_af_ops
> dccp_ipv6_mapped = {
>         .getsockopt        = ipv6_getsockopt,
>         .addr2sockaddr     = inet6_csk_addr2sockaddr,
>         .sockaddr_len      = sizeof(struct sockaddr_in6),
> +       .bind_conflict     = inet6_csk_bind_conflict,
>  #ifdef CONFIG_COMPAT
>         .compat_setsockopt = compat_ipv6_setsockopt,
>         .compat_getsockopt = compat_ipv6_getsockopt,