Date:   Mon, 8 Jan 2018 12:58:11 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+40396d275b34b0dd5dad@...kaller.appspotmail.com>,
        David Miller <davem@...emloft.net>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Tom Herbert <tom@...ntonium.net>,
        Al Viro <viro@...iv.linux.org.uk>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Biggers <ebiggers@...gle.com>,
        netdev <netdev@...r.kernel.org>
Cc:     Lai Jiangshan <jiangshanlai@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com, Tejun Heo <tj@...nel.org>
Subject: Re: KASAN: use-after-free Read in work_is_static_object

On Mon, Jan 8, 2018 at 12:55 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> On Mon, Jan 8, 2018 at 12:43 PM, syzbot
> <syzbot+40396d275b34b0dd5dad@...kaller.appspotmail.com> wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> f66faae2f80a45feafc04ce63ef744ac4b6e8c05
>> 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.
>>
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+40396d275b34b0dd5dad@...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.
>
>
> This looks like an issue in kcm sockets, so +kcm maintainers.

FTR, guilty file extraction was fixed to ignore kernel/workqueue.c:
https://github.com/google/syzkaller/commit/1014e5506e35965f3bad13fabb08666134d0b273
Presumably for bugs in workqueue usually the caller is guilty.


>> device ip6_vti0 entered promiscuous mode
>> ==================================================================
>> BUG: KASAN: use-after-free in constant_test_bit
>> arch/x86/include/asm/bitops.h:325 [inline]
>> BUG: KASAN: use-after-free in work_is_static_object+0x39/0x40
>> kernel/workqueue.c:443
>> Read of size 8 at addr ffff8801beca5788 by task syz-executor2/12922
>>
>> CPU: 0 PID: 12922 Comm: syz-executor2 Not tainted 4.15.0-rc5+ #178
>> 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
>>  constant_test_bit arch/x86/include/asm/bitops.h:325 [inline]
>>  work_is_static_object+0x39/0x40 kernel/workqueue.c:443
>>  debug_object_activate+0x36f/0x730 lib/debugobjects.c:470
>>  debug_work_activate kernel/workqueue.c:492 [inline]
>>  __queue_work+0x163/0x1230 kernel/workqueue.c:1381
>>  queue_work_on+0x16a/0x1c0 kernel/workqueue.c:1487
>>  queue_work include/linux/workqueue.h:488 [inline]
>>  strp_check_rcv+0x25/0x30 net/strparser/strparser.c:552
>>  kcm_attach net/kcm/kcmsock.c:1439 [inline]
>>  kcm_attach_ioctl net/kcm/kcmsock.c:1460 [inline]
>>  kcm_ioctl+0x82f/0x1690 net/kcm/kcmsock.c:1665
>>  sock_do_ioctl+0x65/0xb0 net/socket.c:956
>>  sock_ioctl+0x2c2/0x440 net/socket.c:1053
>>  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+0x23/0x9a
>> RIP: 0033:0x452ac9
>> RSP: 002b:00007f1bbd860c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
>> RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ac9
>> RDX: 0000000020954ff8 RSI: 00000000000089e0 RDI: 0000000000000017
>> RBP: 000000000000057b R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f6428
>> R13: 00000000ffffffff R14: 00007f1bbd8616d4 R15: 0000000000000000
>>
>> Allocated by task 12922:
>>  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
>>  kmem_cache_zalloc include/linux/slab.h:678 [inline]
>>  kcm_attach net/kcm/kcmsock.c:1394 [inline]
>>  kcm_attach_ioctl net/kcm/kcmsock.c:1460 [inline]
>>  kcm_ioctl+0x2d2/0x1690 net/kcm/kcmsock.c:1665
>>  sock_do_ioctl+0x65/0xb0 net/socket.c:956
>>  sock_ioctl+0x2c2/0x440 net/socket.c:1053
>>  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+0x23/0x9a
>>
>> Freed by task 12929:
>>  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
>>  kcm_unattach+0xe53/0x1510 net/kcm/kcmsock.c:1563
>>  kcm_unattach_ioctl net/kcm/kcmsock.c:1608 [inline]
>>  kcm_ioctl+0xe54/0x1690 net/kcm/kcmsock.c:1675
>>  sock_do_ioctl+0x65/0xb0 net/socket.c:956
>>  sock_ioctl+0x2c2/0x440 net/socket.c:1053
>>  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+0x23/0x9a
>>
>> The buggy address belongs to the object at ffff8801beca56c0
>>  which belongs to the cache kcm_psock_cache of size 544
>> The buggy address is located 200 bytes inside of
>>  544-byte region [ffff8801beca56c0, ffff8801beca58e0)
>> The buggy address belongs to the page:
>> page:000000005180a80a count:1 mapcount:0 mapping:0000000058aa9a5c index:0x0
>> compound_mapcount: 0
>> flags: 0x2fffc0000008100(slab|head)
>> raw: 02fffc0000008100 ffff8801beca40c0 0000000000000000 000000010000000b
>> raw: ffff8801d31e8a48 ffff8801d31e8a48 ffff8801d3f6a380 0000000000000000
>> page dumped because: kasan: bad access detected
>>
>> Memory state around the buggy address:
>>  ffff8801beca5680: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>>  ffff8801beca5700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>
>>> ffff8801beca5780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>
>>                       ^
>>  ffff8801beca5800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>  ffff8801beca5880: fb fb fb fb fb fb fb fb fb fb fb fb 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@...glegroups.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
>> To mark this as a duplicate of another syzbot report, please reply with:
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