possible deadlock in ep_free

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    0072a0c14d5b Merge tag 'media/v4.20-4' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14d2796d400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b9cc5a440391cbfd
dashboard link: https://syzkaller.appspot.com/bug?extid=296ea3811c64964727aa
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
userspace arch: i386

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+296ea3811c64964727aa@xxxxxxxxxxxxxxxxxxxxxxxxx


======================================================
WARNING: possible circular locking dependency detected
4.20.0-rc5+ #265 Not tainted
------------------------------------------------------
kworker/0:3/6216 is trying to acquire lock:
000000006d826351 (epmutex){+.+.}, at: ep_free+0xf6/0x300 fs/eventpoll.c:829

but task is already holding lock:
000000005098accc ((delayed_fput_work).work){+.+.}, at:  
process_one_work+0xb9a/0x1c40 kernel/workqueue.c:2128

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 ((delayed_fput_work).work){+.+.}:
       process_one_work+0xc0a/0x1c40 kernel/workqueue.c:2129
       worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
       kthread+0x35a/0x440 kernel/kthread.c:246
       ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

-> #3 ((wq_completion)"events"){+.+.}:
       flush_workqueue+0x30a/0x1e10 kernel/workqueue.c:2655
       flush_scheduled_work include/linux/workqueue.h:599 [inline]
       vim2m_stop_streaming+0x7c/0x2c0 drivers/media/platform/vim2m.c:811
       __vb2_queue_cancel+0x171/0xd20  
drivers/media/common/videobuf2/videobuf2-core.c:1823
       vb2_core_queue_release+0x26/0x80  
drivers/media/common/videobuf2/videobuf2-core.c:2229
       vb2_queue_release+0x15/0x20  
drivers/media/common/videobuf2/videobuf2-v4l2.c:837
       v4l2_m2m_ctx_release+0x2a/0x35  
drivers/media/v4l2-core/v4l2-mem2mem.c:931
       vim2m_release+0xe6/0x150 drivers/media/platform/vim2m.c:977
       v4l2_release+0x224/0x3a0 drivers/media/v4l2-core/v4l2-dev.c:456
       __fput+0x385/0xa30 fs/file_table.c:278
       ____fput+0x15/0x20 fs/file_table.c:309
       task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
       tracehook_notify_resume include/linux/tracehook.h:188 [inline]
       exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
       prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
       syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
       do_syscall_32_irqs_on arch/x86/entry/common.c:341 [inline]
       do_fast_syscall_32+0xcd5/0xfb2 arch/x86/entry/common.c:397
       entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

-> #2 (&dev->dev_mutex){+.+.}:
       __mutex_lock_common kernel/locking/mutex.c:925 [inline]
       __mutex_lock+0x166/0x16f0 kernel/locking/mutex.c:1072
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
       v4l2_m2m_fop_poll+0x98/0x120  
drivers/media/v4l2-core/v4l2-mem2mem.c:1105
       v4l2_poll+0x153/0x200 drivers/media/v4l2-core/v4l2-dev.c:350
       vfs_poll include/linux/poll.h:86 [inline]
       ep_item_poll.isra.15+0x15c/0x400 fs/eventpoll.c:892
       ep_insert+0x781/0x1dd0 fs/eventpoll.c:1464
       __do_sys_epoll_ctl fs/eventpoll.c:2121 [inline]
       __se_sys_epoll_ctl fs/eventpoll.c:2007 [inline]
       __ia32_sys_epoll_ctl+0xeda/0x1080 fs/eventpoll.c:2007
       do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
       do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397
       entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

-> #1 (&ep->mtx){+.+.}:
       __mutex_lock_common kernel/locking/mutex.c:925 [inline]
       __mutex_lock+0x166/0x16f0 kernel/locking/mutex.c:1072
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
       ep_free+0x160/0x300 fs/eventpoll.c:849
       ep_eventpoll_release+0x44/0x60 fs/eventpoll.c:869
       __fput+0x385/0xa30 fs/file_table.c:278
       ____fput+0x15/0x20 fs/file_table.c:309
       task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
       tracehook_notify_resume include/linux/tracehook.h:188 [inline]
       exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
       prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
       syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
       do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (epmutex){+.+.}:
       lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
       __mutex_lock_common kernel/locking/mutex.c:925 [inline]
       __mutex_lock+0x166/0x16f0 kernel/locking/mutex.c:1072
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
       ep_free+0xf6/0x300 fs/eventpoll.c:829
       ep_eventpoll_release+0x44/0x60 fs/eventpoll.c:869
       __fput+0x385/0xa30 fs/file_table.c:278
       delayed_fput+0x55/0x80 fs/file_table.c:304
       process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153
       worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
       kthread+0x35a/0x440 kernel/kthread.c:246
       ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

other info that might help us debug this:

Chain exists of:
  epmutex --> (wq_completion)"events" --> (delayed_fput_work).work

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock((delayed_fput_work).work);
                               lock((wq_completion)"events");
                               lock((delayed_fput_work).work);
  lock(epmutex);

 *** DEADLOCK ***

2 locks held by kworker/0:3/6216:
 #0: 000000000aab2aee ((wq_completion)"events"){+.+.}, at:  
__write_once_size include/linux/compiler.h:209 [inline]
 #0: 000000000aab2aee ((wq_completion)"events"){+.+.}, at:  
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: 000000000aab2aee ((wq_completion)"events"){+.+.}, at: atomic64_set  
include/asm-generic/atomic-instrumented.h:40 [inline]
 #0: 000000000aab2aee ((wq_completion)"events"){+.+.}, at: atomic_long_set  
include/asm-generic/atomic-long.h:59 [inline]
 #0: 000000000aab2aee ((wq_completion)"events"){+.+.}, at: set_work_data  
kernel/workqueue.c:617 [inline]
 #0: 000000000aab2aee ((wq_completion)"events"){+.+.}, at:  
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0: 000000000aab2aee ((wq_completion)"events"){+.+.}, at:  
process_one_work+0xb43/0x1c40 kernel/workqueue.c:2124
 #1: 000000005098accc ((delayed_fput_work).work){+.+.}, at:  
process_one_work+0xb9a/0x1c40 kernel/workqueue.c:2128

stack backtrace:
CPU: 0 PID: 6216 Comm: kworker/0:3 Not tainted 4.20.0-rc5+ #265
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events delayed_fput
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x244/0x39d lib/dump_stack.c:113
 print_circular_bug.isra.35.cold.54+0x1bd/0x27d  
kernel/locking/lockdep.c:1221
 check_prev_add kernel/locking/lockdep.c:1863 [inline]
 check_prevs_add kernel/locking/lockdep.c:1976 [inline]
 validate_chain kernel/locking/lockdep.c:2347 [inline]
 __lock_acquire+0x3399/0x4c20 kernel/locking/lockdep.c:3341
 lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
 __mutex_lock_common kernel/locking/mutex.c:925 [inline]
 __mutex_lock+0x166/0x16f0 kernel/locking/mutex.c:1072
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
 ep_free+0xf6/0x300 fs/eventpoll.c:829
 ep_eventpoll_release+0x44/0x60 fs/eventpoll.c:869
 __fput+0x385/0xa30 fs/file_table.c:278
 delayed_fput+0x55/0x80 fs/file_table.c:304
 process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153
 worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
 kthread+0x35a/0x440 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
audit: type=1326 audit(1543921229.079:66): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=265 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop1' (00000000b08eabe4): kobject_uevent_env
audit: type=1326 audit(1543921229.079:67): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop1' (00000000b08eabe4): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
audit: type=1326 audit(1543921229.079:68): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
audit: type=1326 audit(1543921229.079:69): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921229.079:70): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop0' (00000000c90ec763): kobject_uevent_env
audit: type=1326 audit(1543921229.079:71): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop0' (00000000c90ec763): fill_kobj_path: path  
= '/devices/virtual/block/loop0'
kobject: 'loop3' (00000000287e60d6): kobject_uevent_env
audit: type=1326 audit(1543921229.079:72): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop3' (00000000287e60d6): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
audit: type=1326 audit(1543921229.079:73): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
audit: type=1326 audit(1543921229.079:74): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop2' (00000000a9a0cc13): kobject_uevent_env
audit: type=1326 audit(1543921229.079:75): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop2' (00000000a9a0cc13): fill_kobj_path: path  
= '/devices/virtual/block/loop2'
audit: type=1326 audit(1543921229.079:76): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23841 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop1' (00000000b08eabe4): kobject_uevent_env
kobject: 'loop1' (00000000b08eabe4): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
kobject: 'loop2' (00000000a9a0cc13): kobject_uevent_env
kobject: 'loop2' (00000000a9a0cc13): fill_kobj_path: path  
= '/devices/virtual/block/loop2'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kobject: 'loop0' (00000000c90ec763): kobject_uevent_env
kobject: 'loop0' (00000000c90ec763): fill_kobj_path: path  
= '/devices/virtual/block/loop0'
kobject: 'loop1' (00000000b08eabe4): kobject_uevent_env
kobject: 'loop1' (00000000b08eabe4): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
kobject: 'loop4' (00000000b69c11d9): kobject_uevent_env
kobject: 'loop4' (00000000b69c11d9): fill_kobj_path: path  
= '/devices/virtual/block/loop4'
kobject: 'loop2' (00000000a9a0cc13): kobject_uevent_env
kobject: 'loop2' (00000000a9a0cc13): fill_kobj_path: path  
= '/devices/virtual/block/loop2'
kobject: 'loop0' (00000000c90ec763): kobject_uevent_env
kobject: 'loop0' (00000000c90ec763): fill_kobj_path: path  
= '/devices/virtual/block/loop0'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kobject: 'loop3' (00000000287e60d6): kobject_uevent_env
kobject: 'loop3' (00000000287e60d6): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
kobject: 'loop1' (00000000b08eabe4): kobject_uevent_env
kobject: 'loop1' (00000000b08eabe4): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
kobject: 'loop3' (00000000287e60d6): kobject_uevent_env
kobject: 'loop3' (00000000287e60d6): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kobject: 'loop1' (00000000b08eabe4): kobject_uevent_env
kobject: 'loop1' (00000000b08eabe4): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
kobject: 'loop0' (00000000c90ec763): kobject_uevent_env
kobject: 'loop0' (00000000c90ec763): fill_kobj_path: path  
= '/devices/virtual/block/loop0'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kauditd_printk_skb: 30514 callbacks suppressed
audit: type=1326 audit(1543921234.119:30591): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921234.149:30592): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921234.149:30593): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921234.149:30594): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921234.149:30595): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921234.149:30596): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921234.149:30597): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921234.149:30598): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921234.149:30599): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
audit: type=1326 audit(1543921234.149:30600): auid=4294967295 uid=0 gid=0  
ses=4294967295 subj==unconfined pid=23893 comm="syz-executor4"  
exe="/root/syz-executor4" sig=0 arch=40000003 syscall=240 compat=1  
ip=0xf7f68a29 code=0x50000
kobject: 'loop4' (00000000b69c11d9): kobject_uevent_env
kobject: 'loop4' (00000000b69c11d9): fill_kobj_path: path  
= '/devices/virtual/block/loop4'
kobject: 'loop0' (00000000c90ec763): kobject_uevent_env
kobject: 'loop0' (00000000c90ec763): fill_kobj_path: path  
= '/devices/virtual/block/loop0'
kobject: 'loop2' (00000000a9a0cc13): kobject_uevent_env
kobject: 'loop2' (00000000a9a0cc13): fill_kobj_path: path  
= '/devices/virtual/block/loop2'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kobject: 'loop1' (00000000b08eabe4): kobject_uevent_env
kobject: 'loop1' (00000000b08eabe4): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
kobject: 'loop3' (00000000287e60d6): kobject_uevent_env
kobject: 'loop3' (00000000287e60d6): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kobject: 'loop0' (00000000c90ec763): kobject_uevent_env
kobject: 'loop0' (00000000c90ec763): fill_kobj_path: path  
= '/devices/virtual/block/loop0'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kobject: 'loop1' (00000000b08eabe4): kobject_uevent_env
kobject: 'loop1' (00000000b08eabe4): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
kobject: 'loop3' (00000000287e60d6): kobject_uevent_env
kobject: 'loop3' (00000000287e60d6): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
kobject: 'loop4' (00000000b69c11d9): kobject_uevent_env
kobject: 'loop4' (00000000b69c11d9): fill_kobj_path: path  
= '/devices/virtual/block/loop4'
kobject: 'loop0' (00000000c90ec763): kobject_uevent_env
kobject: 'loop0' (00000000c90ec763): fill_kobj_path: path  
= '/devices/virtual/block/loop0'
kobject: 'loop1' (00000000b08eabe4): kobject_uevent_env
kobject: 'loop1' (00000000b08eabe4): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
kobject: 'loop2' (00000000a9a0cc13): kobject_uevent_env
kobject: 'loop2' (00000000a9a0cc13): fill_kobj_path: path  
= '/devices/virtual/block/loop2'
kobject: 'loop3' (00000000287e60d6): kobject_uevent_env
kobject: 'loop3' (00000000287e60d6): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kobject: 'loop3' (00000000287e60d6): kobject_uevent_env
kobject: 'loop3' (00000000287e60d6): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
kobject: 'loop2' (00000000a9a0cc13): kobject_uevent_env
kobject: 'loop2' (00000000a9a0cc13): fill_kobj_path: path  
= '/devices/virtual/block/loop2'
kobject: 'loop5' (0000000095b64449): kobject_uevent_env
kobject: 'loop5' (0000000095b64449): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kobject: 'loop0' (00000000c90ec763): kobject_uevent_env
kobject: 'loop0' (00000000c90ec763): fill_kobj_path: path  
= '/devices/virtual/block/loop0'


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