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From:   William Tu <u9012063@gmail.com>
Date:   Tue, 23 Jan 2018 10:50:00 -0800
Message-ID: <CALDO+SYScmeUsG5fqngNAuYAZZbPjkfFERKHuKgry_r+W194SA@mail.gmail.com>
Subject: Re: KASAN: slab-out-of-bounds Read in erspan_xmit
To:     David Ahern <dsahern@gmail.com>
Cc:     syzbot <syzbot+9723f2d288e49b492cf0@syzkaller.appspotmail.com>,
        David Miller <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        linux-kernel@vger.kernel.org,
        Linux Kernel Network Developers <netdev@vger.kernel.org>,
        syzkaller-bugs@googlegroups.com,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi,

I'm new to kasan and trying to follow this instruction to reproduce the issue:
https://github.com/google/syzkaller/blob/master/docs/executing_syzkaller_programs.md

After re-compile my kernel with KASAN related config enable, I run
$ ./syz-execprog -cover=0 -repeat=0 -procs=16 program

I wonder does the "program" mean the repro.c.txt? or I should compile
it to binary?
# gcc -o program repro.c.txt
# ./syz-execprog myprogram
2018/01/23 10:45:19 parsed 0 programs

And how to use the "repro.syz.txt"?
It seems to have some command like "syz_emit_ethernet" to generate packet.
but I have no clue where to run it. Maybe I'm still missing something?

Thanks a lot
William

On Mon, Jan 22, 2018 at 2:57 PM, William Tu <u9012063@gmail.com> wrote:
> On Mon, Jan 22, 2018 at 2:45 PM, David Ahern <dsahern@gmail.com> wrote:
>> [ cc William Tu ]
>>
>> On 1/22/18 12:58 PM, syzbot wrote:
>>> Hello,
>>>
>>> syzbot hit the following crash on net-next commit
>>> 9d6474e458b13a94a0d5b141f2b8f38adf1991ae (Mon Jan 22 02:55:38 2018 +0000)
>>> tun: add missing rcu annotation
>>>
>>> So far this crash happened 5 times on net-next.
>>> C reproducer is attached.
>>> syzkaller reproducer is attached.
>>> Raw console output is attached.
>>> compiler: gcc (GCC) 7.1.1 20170620
>>> .config is attached.
>>>
>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>> Reported-by: syzbot+9723f2d288e49b492cf0@syzkaller.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.
>>>
>>> ==================================================================
>>> BUG: KASAN: slab-out-of-bounds in erspan_xmit+0x22d4/0x2430
>>> net/ipv4/ip_gre.c:735
>>> Read of size 2 at addr ffff8801c50bb08b by task syzkaller525754/3647
>>>
>>> CPU: 0 PID: 3647 Comm: syzkaller525754 Not tainted 4.15.0-rc8+ #203
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>>> Google 01/01/2011
>>> Call Trace:
>>>  __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
>>>  __asan_report_load_n_noabort+0xf/0x20 mm/kasan/report.c:440
>>>  erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735
>>>  __netdev_start_xmit include/linux/netdevice.h:4053 [inline]
>>>  netdev_start_xmit include/linux/netdevice.h:4062 [inline]
>>>  packet_direct_xmit+0x3ad/0x790 net/packet/af_packet.c:267
>>>  packet_snd net/packet/af_packet.c:2944 [inline]
>>>  packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2969
>>>  sock_sendmsg_nosec net/socket.c:630 [inline]
>>>  sock_sendmsg+0xca/0x110 net/socket.c:640
>>>  SYSC_sendto+0x361/0x5c0 net/socket.c:1721
>>>  SyS_sendto+0x40/0x50 net/socket.c:1689
>>>  entry_SYSCALL_64_fastpath+0x29/0xa0
>>> RIP: 0033:0x445649
>>> RSP: 002b:00007ffe82dde5b8 EFLAGS: 00000217 ORIG_RAX: 000000000000002c
>>> RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000445649
>>> RDX: 0000000000000000 RSI: 0000000020003fd9 RDI: 0000000000000004
>>> RBP: 00000000004a78c5 R08: 0000000020008000 R09: 000000000000001c
>>> R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000402720
>>> R13: 00000000004027b0 R14: 0000000000000000 R15: 0000000000000000
>>>
>>> Allocated by task 3221:
>>>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>>>  set_track mm/kasan/kasan.c:459 [inline]
>>>  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
>>>  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
>>>  kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
>>>  getname_flags+0xcb/0x580 fs/namei.c:138
>>>  getname+0x19/0x20 fs/namei.c:209
>>>  do_sys_open+0x2e7/0x6d0 fs/open.c:1053
>>>  SYSC_open fs/open.c:1077 [inline]
>>>  SyS_open+0x2d/0x40 fs/open.c:1072
>>>  entry_SYSCALL_64_fastpath+0x29/0xa0
>>>
>>> Freed by task 3221:
>>>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>>>  set_track mm/kasan/kasan.c:459 [inline]
>>>  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
>>>  __cache_free mm/slab.c:3488 [inline]
>>>  kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
>>>  putname+0xee/0x130 fs/namei.c:258
>>>  do_sys_open+0x31b/0x6d0 fs/open.c:1068
>>>  SYSC_open fs/open.c:1077 [inline]
>>>  SyS_open+0x2d/0x40 fs/open.c:1072
>>>  entry_SYSCALL_64_fastpath+0x29/0xa0
>>>
>>> The buggy address belongs to the object at ffff8801c50ba000
>>>  which belongs to the cache names_cache of size 4096
>>> The buggy address is located 139 bytes to the right of
>>>  4096-byte region [ffff8801c50ba000, ffff8801c50bb000)
>>> The buggy address belongs to the page:
>>> page:ffffea0007142e80 count:1 mapcount:0 mapping:ffff8801c50ba000
>>> index:0x0 compound_mapcount: 0
>>> flags: 0x2fffc0000008100(slab|head)
>>> raw: 02fffc0000008100 ffff8801c50ba000 0000000000000000 0000000100000001
>>> raw: ffffea0007145320 ffffea00071433a0 ffff8801dae2c600 0000000000000000
>>> page dumped because: kasan: bad access detected
>>>
>>> Memory state around the buggy address:
>>>  ffff8801c50baf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>  ffff8801c50bb000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>>> ffff8801c50bb080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>>                       ^
>>>  ffff8801c50bb100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>>  ffff8801c50bb180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> ==================================================================
>>>
>>>
>>> ---
>>> This bug is generated by a dumb bot. It may contain errors.
>>> See https://goo.gl/tpsmEJ for details.
>>> Direct all questions to syzkaller@googlegroups.com.
>>>
>>> syzbot will keep track of this bug report.
>>> If you forgot to add the Reported-by tag, once the fix for this bug is
>>> merged
>>> into any tree, please reply to this email with:
>>> #syz fix: exact-commit-title
>>> If you want to test a patch for this bug, please reply with:
>>> #syz test: git://repo/address.git branch
>>> and provide the patch inline or as an attachment.
>>> To mark this as a duplicate of another syzbot report, please reply with:
>>> #syz dup: exact-subject-of-another-report
>>> If it's a one-off invalid bug report, please reply with:
>>> #syz invalid
>>> Note: if the crash happens again, it will cause creation of a new bug
>>> report.
>>> Note: all commands must start from beginning of the line in the email body.
>>
>
> Thanks. I'm working on it.