KASAN: use-after-free Read in get_work_pool

Hello,

syzbot found the following crash on:

HEAD commit: fbc5fe7a Linux 4.14.157
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1027d59ce00000
kernel config: https://syzkaller.appspot.com/x/.config?x=253d29a660cb0d
dashboard link: https://syzkaller.appspot.com/bug?extid=6b501c1f0090a00786d1
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=163ea90ee00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1703fc32e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email protected]

audit: type=1400 audit(1575505903.980:36): avc: denied { map } for
pid=7004 comm="syz-executor412" path="/root/syz-executor412016431"
dev="sda1" ino=16483 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183
[inline]
BUG: KASAN: use-after-free in atomic64_read
arch/x86/include/asm/atomic64_64.h:22 [inline]
BUG: KASAN: use-after-free in atomic_long_read
include/asm-generic/atomic-long.h:45 [inline]
BUG: KASAN: use-after-free in get_work_pool+0x12f/0x150
kernel/workqueue.c:711
Read of size 8 at addr ffff88807e53ca08 by task syz-executor412/7014

CPU: 0 PID: 7014 Comm: syz-executor412 Not tainted 4.14.157-syzkaller #0
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+0x142/0x197 lib/dump_stack.c:58
print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
__read_once_size include/linux/compiler.h:183 [inline]
atomic64_read arch/x86/include/asm/atomic64_64.h:22 [inline]
atomic_long_read include/asm-generic/atomic-long.h:45 [inline]
get_work_pool+0x12f/0x150 kernel/workqueue.c:711
start_flush_work kernel/workqueue.c:2819 [inline]
flush_work+0x117/0x730 kernel/workqueue.c:2884
__cancel_work_timer+0x2f0/0x480 kernel/workqueue.c:2956
cancel_work_sync+0x18/0x20 kernel/workqueue.c:2992
tty_buffer_cancel_work+0x16/0x20 drivers/tty/tty_buffer.c:607
release_tty+0x3f4/0x7c0 drivers/tty/tty_io.c:1507
tty_release_struct+0x3c/0x50 drivers/tty/tty_io.c:1616
tty_release+0xaa3/0xd60 drivers/tty/tty_io.c:1776
__fput+0x275/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x114/0x190 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x7df/0x2ce0 kernel/exit.c:874
do_group_exit+0x111/0x330 kernel/exit.c:977
SYSC_exit_group kernel/exit.c:988 [inline]
SyS_exit_group+0x1d/0x20 kernel/exit.c:986
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x43ff38
RSP: 002b:00007ffc3e5864c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043ff38
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004bf950 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000000000064 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d2180 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7014:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc mm/kasan/kasan.c:551 [inline]
kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
kmem_cache_alloc_trace+0x152/0x790 mm/slab.c:3618
kmalloc include/linux/slab.h:488 [inline]
kzalloc include/linux/slab.h:661 [inline]
vc_allocate drivers/tty/vt/vt.c:772 [inline]
vc_allocate+0x148/0x580 drivers/tty/vt/vt.c:753
con_install+0x52/0x400 drivers/tty/vt/vt.c:2881
tty_driver_install_tty drivers/tty/tty_io.c:1225 [inline]
tty_init_dev drivers/tty/tty_io.c:1338 [inline]
tty_init_dev+0xea/0x3a0 drivers/tty/tty_io.c:1315
tty_open_by_driver drivers/tty/tty_io.c:1973 [inline]
tty_open+0x414/0xa10 drivers/tty/tty_io.c:2021
chrdev_open+0x207/0x590 fs/char_dev.c:423
do_dentry_open+0x73b/0xeb0 fs/open.c:777
vfs_open+0x105/0x220 fs/open.c:891
do_last fs/namei.c:3425 [inline]
path_openat+0x8bd/0x3f70 fs/namei.c:3566
do_filp_open+0x18e/0x250 fs/namei.c:3600
do_sys_open+0x2c5/0x430 fs/open.c:1084
SYSC_open fs/open.c:1102 [inline]
SyS_open+0x2d/0x40 fs/open.c:1097
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 7016:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xcc/0x270 mm/slab.c:3815
vt_disallocate_all+0x286/0x380 drivers/tty/vt/vt_ioctl.c:323
vt_ioctl+0x76b/0x2170 drivers/tty/vt/vt_ioctl.c:816
tty_ioctl+0x841/0x1320 drivers/tty/tty_io.c:2661
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff88807e53ca00
which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 8 bytes inside of
2048-byte region [ffff88807e53ca00, ffff88807e53d200)
The buggy address belongs to the page:
page:ffffea0001f94f00 count:1 mapcount:0 mapping:ffff88807e53c180 index:0x0
compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff88807e53c180 0000000000000000 0000000100000003
raw: ffffea0001f7ab20 ffffea00022649a0 ffff8880aa800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88807e53c900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807e53c980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88807e53ca00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88807e53ca80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807e53cb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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syzbot suspects this bug was fixed by commit:

commit b9eb60a0ef3971101c94f9cddb09708c2f900b35
Author: Eric Biggers <[email protected]>
Date: Sun Mar 22 03:43:04 2020 +0000

vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1427f733e00000
start commit: fbc5fe7a Linux 4.14.157
git tree: linux-4.14.y
If the result looks correct, please mark the bug fixed by replying with:

#syz fix: vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console

For information about bisection process see: https://goo.gl/tpsmEJ#bisection