linux-kernel - Re: KASAN: slab-out-of-bounds Write in tcp_v6_syn_recv

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Date:   Wed, 3 Jan 2018 15:31:04 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Ozgur <ozgur@...sey.org>
Cc:     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 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.