Message-ID: <20200224183003.GB109047@gmail.com>
Date:   Mon, 24 Feb 2020 10:30:03 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     syzbot <syzbot+1024a649601aa4214ff6@...kaller.appspotmail.com>
Cc:     gregkh@...uxfoundation.org, jslaby@...e.com,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: KASAN: use-after-free Read in get_work_pool_id

On Fri, Feb 21, 2020 at 10:58:12AM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    11a48a5a Linux 5.6-rc2
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16554ee6e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b1248cc89e4dba4
> dashboard link: https://syzkaller.appspot.com/bug?extid=1024a649601aa4214ff6
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=112d5aa1e00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16f739d9e00000
> 
> Bisection is inconclusive: the bug happens on the oldest tested release.
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10cbc36ee00000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=12cbc36ee00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=14cbc36ee00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+1024a649601aa4214ff6@...kaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: use-after-free in atomic64_read include/asm-generic/atomic-instrumented.h:836 [inline]
> BUG: KASAN: use-after-free in atomic_long_read include/asm-generic/atomic-long.h:28 [inline]
> BUG: KASAN: use-after-free in get_work_pool_id+0x1c/0xe0 kernel/workqueue.c:732
> Read of size 8 at addr ffff8880a2d36008 by task syz-executor507/9562
> 
> CPU: 1 PID: 9562 Comm: syz-executor507 Not tainted 5.6.0-rc2-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x197/0x210 lib/dump_stack.c:118
>  print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
>  __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506
>  kasan_report+0x12/0x20 mm/kasan/common.c:641
>  check_memory_region_inline mm/kasan/generic.c:185 [inline]
>  check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
>  __kasan_check_read+0x11/0x20 mm/kasan/common.c:95
>  atomic64_read include/asm-generic/atomic-instrumented.h:836 [inline]
>  atomic_long_read include/asm-generic/atomic-long.h:28 [inline]
>  get_work_pool_id+0x1c/0xe0 kernel/workqueue.c:732
>  mark_work_canceling kernel/workqueue.c:743 [inline]
>  __cancel_work_timer+0xfa/0x540 kernel/workqueue.c:3120
>  cancel_work_sync+0x18/0x20 kernel/workqueue.c:3164
>  tty_buffer_cancel_work+0x16/0x20 drivers/tty/tty_buffer.c:613
>  release_tty+0x261/0x470 drivers/tty/tty_io.c:1520
>  tty_release_struct+0x3c/0x50 drivers/tty/tty_io.c:1629
>  tty_release+0xbcb/0xe90 drivers/tty/tty_io.c:1789
>  __fput+0x2ff/0x890 fs/file_table.c:280
>  ____fput+0x16/0x20 fs/file_table.c:313
>  task_work_run+0x145/0x1c0 kernel/task_work.c:113
>  exit_task_work include/linux/task_work.h:22 [inline]
>  do_exit+0xba9/0x2f50 kernel/exit.c:801
>  do_group_exit+0x135/0x360 kernel/exit.c:899
>  __do_sys_exit_group kernel/exit.c:910 [inline]
>  __se_sys_exit_group kernel/exit.c:908 [inline]
>  __x64_sys_exit_group+0x44/0x50 kernel/exit.c:908
>  do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x43ff38
> Code: Bad RIP value.
> RSP: 002b:00007fff706d7d78 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043ff38
> RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
> RBP: 00000000004bf950 R08: 00000000000000e7 R09: ffffffffffffffd0
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> R13: 00000000006d2180 R14: 0000000000000000 R15: 0000000000000000
> 
> Allocated by task 9562:
>  save_stack+0x23/0x90 mm/kasan/common.c:72
>  set_track mm/kasan/common.c:80 [inline]
>  __kasan_kmalloc mm/kasan/common.c:515 [inline]
>  __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:488
>  kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
>  kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3551
>  kmalloc include/linux/slab.h:555 [inline]
>  kzalloc include/linux/slab.h:669 [inline]
>  vc_allocate drivers/tty/vt/vt.c:1085 [inline]
>  vc_allocate+0x1fc/0x760 drivers/tty/vt/vt.c:1066
>  con_install+0x52/0x410 drivers/tty/vt/vt.c:3229
>  tty_driver_install_tty drivers/tty/tty_io.c:1228 [inline]
>  tty_init_dev drivers/tty/tty_io.c:1341 [inline]
>  tty_init_dev+0xf9/0x470 drivers/tty/tty_io.c:1318
>  tty_open_by_driver drivers/tty/tty_io.c:1987 [inline]
>  tty_open+0x4a5/0xbb0 drivers/tty/tty_io.c:2035
>  chrdev_open+0x245/0x6b0 fs/char_dev.c:414
>  do_dentry_open+0x4e6/0x1380 fs/open.c:797
>  vfs_open+0xa0/0xd0 fs/open.c:914
>  do_last fs/namei.c:3490 [inline]
>  path_openat+0x12ee/0x3490 fs/namei.c:3607
>  do_filp_open+0x192/0x260 fs/namei.c:3637
>  do_sys_openat2+0x5eb/0x7e0 fs/open.c:1149
>  do_sys_open+0xf2/0x180 fs/open.c:1165
>  ksys_open include/linux/syscalls.h:1386 [inline]
>  __do_sys_open fs/open.c:1171 [inline]
>  __se_sys_open fs/open.c:1169 [inline]
>  __x64_sys_open+0x7e/0xc0 fs/open.c:1169
>  do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 9566:
>  save_stack+0x23/0x90 mm/kasan/common.c:72
>  set_track mm/kasan/common.c:80 [inline]
>  kasan_set_free_info mm/kasan/common.c:337 [inline]
>  __kasan_slab_free+0x102/0x150 mm/kasan/common.c:476
>  kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
>  __cache_free mm/slab.c:3426 [inline]
>  kfree+0x10a/0x2c0 mm/slab.c:3757
>  vt_disallocate_all+0x2bd/0x3e0 drivers/tty/vt/vt_ioctl.c:323
>  vt_ioctl+0xc38/0x26d0 drivers/tty/vt/vt_ioctl.c:816
>  tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2660
>  vfs_ioctl fs/ioctl.c:47 [inline]
>  ksys_ioctl+0x123/0x180 fs/ioctl.c:763
>  __do_sys_ioctl fs/ioctl.c:772 [inline]
>  __se_sys_ioctl fs/ioctl.c:770 [inline]
>  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
>  do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> The buggy address belongs to the object at ffff8880a2d36000
>  which belongs to the cache kmalloc-2k of size 2048
> The buggy address is located 8 bytes inside of
>  2048-byte region [ffff8880a2d36000, ffff8880a2d36800)
> The buggy address belongs to the page:
> page:ffffea00028b4d80 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0
> flags: 0xfffe0000000200(slab)
> raw: 00fffe0000000200 ffffea00028bcbc8 ffffea0002915c88 ffff8880aa400e00
> raw: 0000000000000000 ffff8880a2d36000 0000000100000001 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff8880a2d35f00: 00 fc fc 00 00 00 00 00 fc fc 00 00 00 00 00 fc
>  ffff8880a2d35f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >ffff8880a2d36000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                       ^
>  ffff8880a2d36080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8880a2d36100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================

#syz dup: KASAN: use-after-free Write in release_tty

(Thread link: https://lkml.kernel.org/lkml/0000000000006663de0598d25ab1@google.com/)

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