WARNING in __flush_work

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: a03957ab Linux 4.19.38
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11dc1bcca00000
kernel config: https://syzkaller.appspot.com/x/.config?x=dd6b74381d776865
dashboard link: https://syzkaller.appspot.com/bug?extid=4eb909ad0ee2bbcbd6a3
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4eb909...@syzkaller.appspotmail.com

WARNING: CPU: 1 PID: 32099 at kernel/workqueue.c:2911
__flush_work+0x740/0x880 kernel/workqueue.c:2911
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 32099 Comm: kworker/1:3 Not tainted 4.19.38 #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: md_misc mddev_delayed_delete
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
panic+0x263/0x51d kernel/panic.c:185
kobject: 'loop2' (0000000061a430d3): kobject_uevent_env
kobject: 'loop2' (0000000061a430d3): fill_kobj_path: path
= '/devices/virtual/block/loop2'
__warn.cold+0x20/0x54 kernel/panic.c:540
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x204/0x360 arch/x86/kernel/traps.c:296
kobject: 'loop0' (000000008538d249): kobject_uevent_env
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:997
RIP: 0010:__flush_work+0x740/0x880 kernel/workqueue.c:2911
Code: 74 58 e8 63 59 25 00 fb 66 0f 1f 44 00 00 45 31 e4 e9 86 fd ff ff e8
4f 59 25 00 0f 0b 45 31 e4 e9 77 fd ff ff e8 40 59 25 00 <0f> 0b 45 31 e4
e9 68 fd ff ff e8 31 59 25 00 4c 89 ff 45 31 e4 e8
RSP: 0018:ffff8880430d7990 EFLAGS: 00010293
kobject: 'loop0' (000000008538d249): fill_kobj_path: path
= '/devices/virtual/block/loop0'
RAX: ffff8880a96a2680 RBX: dffffc0000000000 RCX: ffffffff8146100b
RDX: 0000000000000000 RSI: ffffffff814616b0 RDI: 0000000000000001
RBP: ffff8880430d7af8 R08: ffff8880a96a2680 R09: ffff8880a96a2f48
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88809b1a5690
kobject: 'loop2' (0000000061a430d3): kobject_uevent_env
R13: ffff8880430d7ad0 R14: 0000000000000001 R15: 0000000000000001
kobject: 'loop2' (0000000061a430d3): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop0' (000000008538d249): kobject_uevent_env
__cancel_work_timer+0x3bf/0x520 kernel/workqueue.c:3007
kobject: 'loop0' (000000008538d249): fill_kobj_path: path
= '/devices/virtual/block/loop0'
cancel_work_sync+0x18/0x20 kernel/workqueue.c:3043
blk_sync_queue+0x33/0x1c0 block/blk-core.c:408
blk_cleanup_queue+0x404/0x720 block/blk-core.c:807
md_free+0xcb/0x1b0 drivers/md/md.c:5223
kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put.cold+0x28f/0x2ec lib/kobject.c:708
kobject: 'loop2' (0000000061a430d3): kobject_uevent_env
mddev_delayed_delete+0x34/0x40 drivers/md/md.c:5251
process_one_work+0x98e/0x1760 kernel/workqueue.c:2153
worker_thread+0x98/0xe40 kernel/workqueue.c:2296
kobject: 'loop2' (0000000061a430d3): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kthread+0x357/0x430 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot will keep track of this bug report. See:
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[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: a03957ab Linux 4.19.38
git tree: linux-4.19.y

console output: https://syzkaller.appspot.com/x/log.txt?x=11d2ee48a00000

kernel config: https://syzkaller.appspot.com/x/.config?x=dd6b74381d776865
dashboard link: https://syzkaller.appspot.com/bug?extid=4eb909ad0ee2bbcbd6a3
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1441ba70a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ade4fca00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4eb909...@syzkaller.appspotmail.com

audit: type=1400 audit(1556790458.234:36): avc: denied { map } for
pid=8168 comm="syz-executor461" path="/root/syz-executor461427238"
dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
IPVS: ftp: loaded support on port[0] = 21
md: md0 stopped.
WARNING: CPU: 1 PID: 3214 at kernel/workqueue.c:2911

__flush_work+0x740/0x880 kernel/workqueue.c:2911
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3214 Comm: kworker/1:2 Not tainted 4.19.38 #6

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: md_misc mddev_delayed_delete
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
panic+0x263/0x51d kernel/panic.c:185

__warn.cold+0x20/0x54 kernel/panic.c:540
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x204/0x360 arch/x86/kernel/traps.c:296

do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:997
RIP: 0010:__flush_work+0x740/0x880 kernel/workqueue.c:2911
Code: 74 58 e8 63 59 25 00 fb 66 0f 1f 44 00 00 45 31 e4 e9 86 fd ff ff e8
4f 59 25 00 0f 0b 45 31 e4 e9 77 fd ff ff e8 40 59 25 00 <0f> 0b 45 31 e4
e9 68 fd ff ff e8 31 59 25 00 4c 89 ff 45 31 e4 e8

RSP: 0018:ffff88809bc3f990 EFLAGS: 00010293
RAX: ffff88809bc10640 RBX: dffffc0000000000 RCX: ffffffff8146100b

RDX: 0000000000000000 RSI: ffffffff814616b0 RDI: 0000000000000001

RBP: ffff88809bc3faf8 R08: ffff88809bc10640 R09: ffff88809bc10f08
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88809aca8690
R13: ffff88809bc3fad0 R14: 0000000000000001 R15: 0000000000000001
__cancel_work_timer+0x3bf/0x520 kernel/workqueue.c:3007

cancel_work_sync+0x18/0x20 kernel/workqueue.c:3043
blk_sync_queue+0x33/0x1c0 block/blk-core.c:408
blk_cleanup_queue+0x404/0x720 block/blk-core.c:807
md_free+0xcb/0x1b0 drivers/md/md.c:5223
kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put.cold+0x28f/0x2ec lib/kobject.c:708

mddev_delayed_delete+0x34/0x40 drivers/md/md.c:5251
process_one_work+0x98e/0x1760 kernel/workqueue.c:2153
worker_thread+0x98/0xe40 kernel/workqueue.c:2296

[syzbot]

syzbot suspects this bug was fixed by commit:

commit af48f7d79faeaa9f426b400c6ec332fe669553e0
Author: Thomas Zimmermann <tzimm...@suse.de>
Date: Mon Jul 15 18:05:57 2019 +0000

drm/udl: Replace drm_dev_unref with drm_dev_put

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14e2d0a6e00000
start commit: a03957ab Linux 4.19.38
git tree: linux-4.19.y

kernel config: https://syzkaller.appspot.com/x/.config?x=dd6b74381d776865
dashboard link: https://syzkaller.appspot.com/bug?extid=4eb909ad0ee2bbcbd6a3

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1441ba70a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ade4fca00000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: drm/udl: Replace drm_dev_unref with drm_dev_put

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