netdev - Re: KASAN: slab-out-of-bounds Write in tcp_v6_syn_recv

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Date:   Tue, 16 Jan 2018 08:43:02 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Ozgur <ozgur@...sey.org>,
        syzbot <syzbot+6dc95bddc6976b800b0b@...kaller.appspotmail.com>,
        David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        "avejwatson@...com" <avejwatson@...com>,
        "ilyal@...lanox.com" <ilyal@...lanox.com>,
        "aviadye@...lanox.com" <aviadye@...lanox.com>
Subject: Re: KASAN: slab-out-of-bounds Write in tcp_v6_syn_recv_sock

On Thu, Jan 4, 2018 at 12:31 AM, Cong Wang <xiyou.wangcong@...il.com> wrote:
> On Wed, Jan 3, 2018 at 12:55 PM, Ozgur <ozgur@...sey.org> wrote:
>>
>>
>> 03.01.2018, 21:57, "Cong Wang" <xiyou.wangcong@...il.com>:
>>> On Tue, Jan 2, 2018 at 3:58 PM, syzbot
>>> <syzbot+6dc95bddc6976b800b0b@...kaller.appspotmail.com> wrote:
>>>>  Hello,
>>>>
>>>>  syzkaller hit the following crash on
>>>>  61233580f1f33c50e159c50e24d80ffd2ba2e06b
>>>>  git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
>>>>  compiler: gcc (GCC) 7.1.1 20170620
>>>>  .config is attached
>>>>  Raw console output is attached.
>>>>  C reproducer is attached
>>>>  syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>>>>  for information about syzkaller reproducers
>>>>
>>>>  IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>>>  Reported-by: syzbot+6dc95bddc6976b800b0b@...kaller.appspotmail.com
>>>>  It will help syzbot understand when the bug is fixed. See footer for
>>>>  details.
>>>>  If you forward the report, please keep this part and the footer.
>>>>
>>>>  TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending
>>>>  cookies. Check SNMP counters.
>>>>  ==================================================================
>>>>  BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:344 [inline]
>>>>  BUG: KASAN: slab-out-of-bounds in tcp_v6_syn_recv_sock+0x628/0x23a0
>>>>  net/ipv6/tcp_ipv6.c:1144
>>>>  Write of size 160 at addr ffff8801cbdd7460 by task syzkaller545407/3196
>>>>
>>>>  CPU: 1 PID: 3196 Comm: syzkaller545407 Not tainted 4.15.0-rc5+ #241
>>>>  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>>>>  Google 01/01/2011
>>>>  Call Trace:
>>>>   <IRQ>
>>>>   __dump_stack lib/dump_stack.c:17 [inline]
>>>>   dump_stack+0x194/0x257 lib/dump_stack.c:53
>>>>   print_address_description+0x73/0x250 mm/kasan/report.c:252
>>>>   kasan_report_error mm/kasan/report.c:351 [inline]
>>>>   kasan_report+0x25b/0x340 mm/kasan/report.c:409
>>>>   check_memory_region_inline mm/kasan/kasan.c:260 [inline]
>>>>   check_memory_region+0x137/0x190 mm/kasan/kasan.c:267
>>>>   memcpy+0x37/0x50 mm/kasan/kasan.c:303
>>>>   memcpy include/linux/string.h:344 [inline]
>>>>   tcp_v6_syn_recv_sock+0x628/0x23a0 net/ipv6/tcp_ipv6.c:1144
>>>
>>> tls_init() changes sk->sk_prot from IPv6 to IPv4, which leads
>>> to this bug. I guess IPv6 is not supported for TLS? If so, need
>>> a check on proto in tls_init()...
>>
>> Hello,
>>
>> I think IPv6 supports with TLS.
>> There was a previously posted commit by Mellanox:
>>
>> https://patchwork.ozlabs.org/patch/801530/
>
> Good to know.
>
> Can you resend the fix? It could probably fix another warning
> reported by syzbot too.

FTR this has been assigned CVE-2018-5703