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Subject[syzbot] possible deadlock in blkdev_get_by_dev
From
Hello,

syzbot found the following issue on:

HEAD commit: fc74e0a40e4f Linux 5.16-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17d0e97eb00000
kernel config: https://syzkaller.appspot.com/x/.config?x=1a86c22260afac2f
dashboard link: https://syzkaller.appspot.com/bug?extid=a1db28a5dacdaf16ffde
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a1db28a5dacdaf16ffde@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.16.0-rc7-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.1/13014 is trying to acquire lock:
ffff88801b64d918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev.part.0+0x40e/0xc70 block/bdev.c:817

but task is already holding lock:
ffffffff8ba51e28 (system_transition_mutex/1){+.+.}-{3:3}, at: software_resume.part.0+0x19/0x1f0 kernel/power/hibernate.c:934

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (system_transition_mutex/1){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
software_resume.part.0+0x19/0x1f0 kernel/power/hibernate.c:934
software_resume kernel/power/hibernate.c:86 [inline]
resume_store+0x161/0x190 kernel/power/hibernate.c:1181
kobj_attr_store+0x50/0x80 lib/kobject.c:856
sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:136
kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write+0x429/0x660 fs/read_write.c:503
vfs_write+0x7cd/0xae0 fs/read_write.c:590
ksys_write+0x12d/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #6 (&of->mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
kernfs_seq_start+0x4b/0x260 fs/kernfs/file.c:112
seq_read_iter+0x2c6/0x1280 fs/seq_file.c:225
kernfs_fop_read_iter+0x44f/0x5f0 fs/kernfs/file.c:241
call_read_iter include/linux/fs.h:2156 [inline]
new_sync_read+0x421/0x6e0 fs/read_write.c:400
vfs_read+0x35c/0x600 fs/read_write.c:481
ksys_read+0x12d/0x250 fs/read_write.c:619
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #5 (&p->lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
seq_read_iter+0xdf/0x1280 fs/seq_file.c:182
call_read_iter include/linux/fs.h:2156 [inline]
generic_file_splice_read+0x453/0x6d0 fs/splice.c:311
do_splice_to+0x1bf/0x250 fs/splice.c:796
splice_direct_to_actor+0x2c2/0x8c0 fs/splice.c:870
do_splice_direct+0x1b3/0x280 fs/splice.c:979
do_sendfile+0xaf2/0x1250 fs/read_write.c:1245
__do_sys_sendfile64 fs/read_write.c:1310 [inline]
__se_sys_sendfile64 fs/read_write.c:1296 [inline]
__x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1296
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #4 (sb_writers#3){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1810 [inline]
sb_start_write include/linux/fs.h:1880 [inline]
file_start_write include/linux/fs.h:3008 [inline]
lo_write_bvec drivers/block/loop.c:242 [inline]
lo_write_simple drivers/block/loop.c:265 [inline]
do_req_filebacked drivers/block/loop.c:494 [inline]
loop_handle_cmd drivers/block/loop.c:1857 [inline]
loop_process_work+0x1499/0x1db0 drivers/block/loop.c:1897
process_one_work+0x9b2/0x1660 kernel/workqueue.c:2298
worker_thread+0x65d/0x1130 kernel/workqueue.c:2445
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

-> #3 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}:
process_one_work+0x921/0x1660 kernel/workqueue.c:2274
worker_thread+0x65d/0x1130 kernel/workqueue.c:2445
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

-> #2 ((wq_completion)loop4){+.+.}-{0:0}:
flush_workqueue+0x110/0x13a0 kernel/workqueue.c:2818
drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2983
destroy_workqueue+0x71/0x800 kernel/workqueue.c:4420
__loop_clr_fd+0x1de/0x1070 drivers/block/loop.c:1124
lo_release+0x1ac/0x1f0 drivers/block/loop.c:1761
blkdev_put_whole block/bdev.c:694 [inline]
blkdev_put+0x2de/0x950 block/bdev.c:957
deactivate_locked_super+0x94/0x160 fs/super.c:335
deactivate_super+0xad/0xd0 fs/super.c:366
cleanup_mnt+0x3a2/0x540 fs/namespace.c:1137
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #1 (&lo->lo_mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
lo_open+0x75/0x120 drivers/block/loop.c:1733
blkdev_get_whole+0x99/0x2d0 block/bdev.c:671
blkdev_get_by_dev.part.0+0x5c6/0xc70 block/bdev.c:826
blkdev_get_by_dev+0x6b/0x80 block/bdev.c:860
blkdev_open+0x154/0x2e0 block/fops.c:501
do_dentry_open+0x4b9/0x1240 fs/open.c:822
do_open fs/namei.c:3426 [inline]
path_openat+0x1cad/0x2750 fs/namei.c:3559
do_filp_open+0x1aa/0x400 fs/namei.c:3586
do_sys_openat2+0x16d/0x4d0 fs/open.c:1212
do_sys_open fs/open.c:1228 [inline]
__do_sys_openat fs/open.c:1244 [inline]
__se_sys_openat fs/open.c:1239 [inline]
__x64_sys_openat+0x13f/0x1f0 fs/open.c:1239
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (&disk->open_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3063 [inline]
check_prevs_add kernel/locking/lockdep.c:3186 [inline]
validate_chain kernel/locking/lockdep.c:3801 [inline]
__lock_acquire+0x2a2c/0x5470 kernel/locking/lockdep.c:5027
lock_acquire kernel/locking/lockdep.c:5637 [inline]
lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
blkdev_get_by_dev.part.0+0x40e/0xc70 block/bdev.c:817
blkdev_get_by_dev+0x6b/0x80 block/bdev.c:860
swsusp_check+0x97/0x2f0 kernel/power/swap.c:1520
software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:979
software_resume kernel/power/hibernate.c:86 [inline]
resume_store+0x161/0x190 kernel/power/hibernate.c:1181
kobj_attr_store+0x50/0x80 lib/kobject.c:856
sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:136
kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write+0x429/0x660 fs/read_write.c:503
vfs_write+0x7cd/0xae0 fs/read_write.c:590
ksys_write+0x12d/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Chain exists of:
&disk->open_mutex --> &of->mutex --> system_transition_mutex/1

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(system_transition_mutex/1);
lock(&of->mutex);
lock(system_transition_mutex/1);
lock(&disk->open_mutex);

*** DEADLOCK ***

5 locks held by syz-executor.1/13014:
#0: ffff888021bff9f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:1034
#1: ffff888022bf0460 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x12d/0x250 fs/read_write.c:643
#2: ffff888073515888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x287/0x500 fs/kernfs/file.c:287
#3: ffff888011918830 (kn->active#782){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2ab/0x500 fs/kernfs/file.c:288
#4: ffffffff8ba51e28 (system_transition_mutex/1){+.+.}-{3:3}, at: software_resume.part.0+0x19/0x1f0 kernel/power/hibernate.c:934

stack backtrace:
CPU: 0 PID: 13014 Comm: syz-executor.1 Not tainted 5.16.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2143
check_prev_add kernel/locking/lockdep.c:3063 [inline]
check_prevs_add kernel/locking/lockdep.c:3186 [inline]
validate_chain kernel/locking/lockdep.c:3801 [inline]
__lock_acquire+0x2a2c/0x5470 kernel/locking/lockdep.c:5027
lock_acquire kernel/locking/lockdep.c:5637 [inline]
lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
__mutex_lock_common kernel/locking/mutex.c:607 [inline]
__mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740
blkdev_get_by_dev.part.0+0x40e/0xc70 block/bdev.c:817
blkdev_get_by_dev+0x6b/0x80 block/bdev.c:860
swsusp_check+0x97/0x2f0 kernel/power/swap.c:1520
software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:979
software_resume kernel/power/hibernate.c:86 [inline]
resume_store+0x161/0x190 kernel/power/hibernate.c:1181
kobj_attr_store+0x50/0x80 lib/kobject.c:856
sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:136
kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write+0x429/0x660 fs/read_write.c:503
vfs_write+0x7cd/0xae0 fs/read_write.c:590
ksys_write+0x12d/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7eff8b85ae99
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007eff8a1d0168 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007eff8b96df60 RCX: 00007eff8b85ae99
RDX: 0000000000000012 RSI: 0000000020000080 RDI: 0000000000000004
RBP: 00007eff8b8b4ff1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff843e579f R14: 00007eff8a1d0300 R15: 0000000000022000
</TASK>
PM: Image not found (code -22)


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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