WARNING in kernfs

WARNING in kernfs_get (2)
Status: upstream: reported on 2020/09/08 18:19
Reported-by: syzbot+d41ab07507be715b63f5@syzkaller.appspotmail.com
First crash: 24d, last: 2d01h

similar bugs (4):
Kernel	Title	Repro	Bisected	Count	Last	Reported	Patched	Status
linux-4.19	WARNING in kernfs_get	C	fix	14	382d	522d	1/1	fixed on 2019/12/05 23:59
linux-4.14	WARNING in kernfs_get	C	fix	17	406d	526d	1/1	fixed on 2019/12/07 19:24
upstream	WARNING in kernfs_get	C	cause	316	421d	749d	14/17	fixed on 2019/11/20 22:01
android-414	WARNING in kernfs_get	syz		69	385d	537d	0/1	public: reported syz repro on 2019/04/10 15:44

Sample crash report:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 6869 at fs/kernfs/dir.c:494 kernfs_get.part.0+0x69/0x80 fs/kernfs/dir.c:494
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 6869 Comm: syz-executor.0 Not tainted 5.9.0-rc6-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+0x198/0x1fd lib/dump_stack.c:118
 panic+0x382/0x7fb kernel/panic.c:231
 __warn.cold+0x20/0x4b kernel/panic.c:600
 report_bug+0x1bd/0x210 lib/bug.c:198
 handle_bug+0x38/0x90 arch/x86/kernel/traps.c:234
 exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:254
 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:536
RIP: 0010:kernfs_get.part.0+0x69/0x80 fs/kernfs/dir.c:494
Code: 31 ff 89 ee e8 88 7a 8a ff 85 ed 74 18 e8 1f 7e 8a ff be 04 00 00 00 48 89 df e8 b2 23 cb ff f0 ff 03 5b 5d c3 e8 07 7e 8a ff <0f> 0b eb df 48 89 df e8 3b 51 cb ff eb c6 66 0f 1f 84 00 00 00 00
RSP: 0018:ffffc90005757b70 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888000158cf0 RCX: ffffffff81ebc018
RDX: ffff888056e54040 RSI: ffffffff81ebc039 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: ffff888000158cf3
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888000158cf0
R13: 0000000000000000 R14: ffff8880a0646630 R15: ffff8880a06465e0
 kernfs_get fs/kernfs/dir.c:493 [inline]
 kernfs_find_and_get_ns+0x44/0x60 fs/kernfs/dir.c:907
 kernfs_find_and_get include/linux/kernfs.h:548 [inline]
 sysfs_unmerge_group+0x5d/0x160 fs/sysfs/group.c:366
 dpm_sysfs_remove+0x62/0xb0 drivers/base/power/sysfs.c:797
 device_del+0x18b/0xd90 drivers/base/core.c:3080
 device_unregister+0x11/0x30 drivers/base/core.c:3135
 bdi_unregister+0x3e0/0x590 mm/backing-dev.c:877
 release_bdi+0xa1/0xc0 mm/backing-dev.c:893
 kref_put include/linux/kref.h:65 [inline]
 bdi_put+0x72/0xa0 mm/backing-dev.c:901
 generic_shutdown_super+0x2aa/0x370 fs/super.c:478
 kill_anon_super+0x36/0x60 fs/super.c:1108
 deactivate_locked_super+0x94/0x160 fs/super.c:335
 deactivate_super+0xad/0xd0 fs/super.c:366
 cleanup_mnt+0x3a3/0x530 fs/namespace.c:1118
 task_work_run+0xdd/0x190 kernel/task_work.c:141
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:165 [inline]
 exit_to_user_mode_prepare+0x1e1/0x200 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x7e/0x2e0 kernel/entry/common.c:267
 __do_fast_syscall_32+0x6c/0x90 arch/x86/entry/common.c:138
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7f7b549
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000090bed1c EFLAGS: 00000212 ORIG_RAX: 0000000000000034
RAX: 0000000000000000 RBX: 00000000090bedac RCX: 0000000000000002
RDX: 0000000009da8228 RSI: 0000000009da8270 RDI: 00000000080d8bbe
RBP: 00000000090bedac R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..

Crashes (2):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Maintainers
ci-upstream-kasan-gce-386	2020/09/27 03:54	upstream	eeddbe68	2d5ea0cb	.config	log	report			info	gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, tj@kernel.org
ci-upstream-linux-next-kasan-gce-root	2020/09/04 18:17	linux-next	7a695657	abf9ba4f	.config	log	report				gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, tj@kernel.org