netdev - Re: KASAN: use-after-free Read in worker

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Message-ID: <CACT4Y+ZQa2fZ9dyOyW_Rtjo8LtrjKuXDm1cmOgTy2iU4CEyVGQ@mail.gmail.com>
Date:   Tue, 14 Nov 2017 09:09:36 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     syzbot 
        <bot+bdfa5a20d5d091fffa3d4e8d37ec24962970ebd0@...kaller.appspotmail.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com, Tejun Heo <tj@...nel.org>,
        David Miller <davem@...emloft.net>, tom@...ntonium.net,
        Eric Biggers <ebiggers@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Tobias Klauser <tklauser@...tanz.ch>,
        netdev <netdev@...r.kernel.org>
Subject: Re: KASAN: use-after-free Read in worker_thread (2)

On Fri, Nov 10, 2017 at 7:49 PM, Cong Wang <xiyou.wangcong@...il.com> wrote:
> On Wed, Nov 8, 2017 at 5:00 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
>> On Wed, Nov 8, 2017 at 1:58 PM, syzbot
>> <bot+bdfa5a20d5d091fffa3d4e8d37ec24962970ebd0@...kaller.appspotmail.com>
>> wrote:
>>> Hello,
>>>
>>> syzkaller hit the following crash on
>>> 7dfaa7bc99498da1c6c4a48bee8d2d5265161a8c
>>> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
>>> compiler: gcc (GCC) 7.1.1 20170620
>>> .config is attached
>>> Raw console output is attached.
>>>
>>> Unfortunately, I don't have any reproducer for this bug yet.
>>>
>>
>>
>> I guess this is more about kcmsock.c rather than workqueue.c. +kcm maintainers.
>
>
> Looks like the work is not cancelled before being freed on this path.
> Do you have a C reproducer for me to try?

This is answered in the email text and the referenced link. If the
wording is not clear, we should improve it.


>>> ==================================================================
>>> BUG: KASAN: use-after-free in worker_thread+0x15bb/0x1990
>>> kernel/workqueue.c:2245
>>> Read of size 8 at addr ffff8801c3a74110 by task kworker/u4:6/3515
>>>
>>> CPU: 1 PID: 3515 Comm: kworker/u4:6 Not tainted 4.14.0-rc7+ #112
>>> 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_load8_noabort+0x14/0x20 mm/kasan/report.c:430
>>>  worker_thread+0x15bb/0x1990 kernel/workqueue.c:2245
>>>  kthread+0x35e/0x430 kernel/kthread.c:231
>>>  ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:432
>>>
>>> Allocated by task 31482:
>>>  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
>>>  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:3562
>>>  kmem_cache_zalloc include/linux/slab.h:657 [inline]
>>>  kcm_attach net/kcm/kcmsock.c:1394 [inline]
>>>  kcm_attach_ioctl net/kcm/kcmsock.c:1460 [inline]
>>>  kcm_ioctl+0x2d1/0x1610 net/kcm/kcmsock.c:1695
>>>  sock_do_ioctl+0x65/0xb0 net/socket.c:961
>>>  sock_ioctl+0x2c2/0x440 net/socket.c:1058
>>>  vfs_ioctl fs/ioctl.c:46 [inline]
>>>  do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
>>>  SYSC_ioctl fs/ioctl.c:701 [inline]
>>>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>>>  entry_SYSCALL_64_fastpath+0x1f/0xbe
>>>
>>> Freed by task 1249:
>>>  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
>>>  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:3504 [inline]
>>>  kmem_cache_free+0x77/0x280 mm/slab.c:3764
>>>  unreserve_psock+0x5a1/0x780 net/kcm/kcmsock.c:547
>>>  kcm_write_msgs+0xbae/0x1b80 net/kcm/kcmsock.c:590
>>>  kcm_tx_work+0x2e/0x190 net/kcm/kcmsock.c:731
>>>  process_one_work+0xbf0/0x1bc0 kernel/workqueue.c:2113
>>>  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
>>>  kthread+0x35e/0x430 kernel/kthread.c:231
>>>  ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:432
>>>
>>> The buggy address belongs to the object at ffff8801c3a74040
>>>  which belongs to the cache kcm_psock_cache of size 552
>>> The buggy address is located 208 bytes inside of
>>>  552-byte region [ffff8801c3a74040, ffff8801c3a74268)
>>> The buggy address belongs to the page:
>>> page:ffffea00070e9d00 count:1 mapcount:0 mapping:ffff8801c3a74040 index:0x0
>>> compound_mapcount: 0
>>> flags: 0x2fffc0000008100(slab|head)
>>> raw: 02fffc0000008100 ffff8801c3a74040 0000000000000000 000000010000000b
>>> raw: ffffea00067920a0 ffff8801d3f39948 ffff8801d3f2a840 0000000000000000
>>> page dumped because: kasan: bad access detected
>>>
>>> Memory state around the buggy address:
>>>  ffff8801c3a74000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>>>  ffff8801c3a74080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>
>>>> ffff8801c3a74100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>
>>>                          ^
>>>  ffff8801c3a74180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>  ffff8801c3a74200: fb fb fb fb fb fb fb fb fb fb fb fb fb 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@...glegroups.com.
>>> Please credit me with: Reported-by: syzbot <syzkaller@...glegroups.com>
>>>
>>> syzbot will keep track of this bug report.
>>> Once a fix for this bug is committed, please reply to this email with:
>>> #syz fix: exact-commit-title
>>> 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.
>>>
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