======================================================
WARNING: possible circular locking dependency detected
4.14.0-rc2+ #10 Not tainted
------------------------------------------------------
syzkaller821047/2981 is trying to acquire lock:
(&bdev->bd_mutex){+.+.}, at: [<ffffffff8232c60e>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:192
but task is already holding lock:
(&lo->lo_ctl_mutex#2){+.+.}, at: [<ffffffff83541ef9>] lo_compat_ioctl+0x109/0x140 drivers/block/loop.c:1533
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&lo->lo_ctl_mutex#2){+.+.}:
check_prevs_add kernel/locking/lockdep.c:2020 [inline]
validate_chain kernel/locking/lockdep.c:2469 [inline]
__lock_acquire+0x328f/0x4620 kernel/locking/lockdep.c:3498
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0x16f/0x19d0 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
lo_release+0x6b/0x180 drivers/block/loop.c:1587
__blkdev_put+0x602/0x7c0 fs/block_dev.c:1780
blkdev_put+0x85/0x4f0 fs/block_dev.c:1845
blkdev_close+0x91/0xc0 fs/block_dev.c:1852
__fput+0x333/0x7f0 fs/file_table.c:210
____fput+0x15/0x20 fs/file_table.c:244
task_work_run+0x199/0x270 kernel/task_work.c:112
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x296/0x310 arch/x86/entry/common.c:162
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath+0x42f/0x510 arch/x86/entry/common.c:266
entry_SYSCALL_64_fastpath+0xbc/0xbe
-> #0 (&bdev->bd_mutex){+.+.}:
check_prev_add+0x865/0x1520 kernel/locking/lockdep.c:1894
check_prevs_add kernel/locking/lockdep.c:2020 [inline]
validate_chain kernel/locking/lockdep.c:2469 [inline]
__lock_acquire+0x328f/0x4620 kernel/locking/lockdep.c:3498
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0x16f/0x19d0 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
blkdev_reread_part+0x1e/0x40 block/ioctl.c:192
loop_reread_partitions+0x12f/0x1a0 drivers/block/loop.c:614
loop_set_status+0x9ba/0xf60 drivers/block/loop.c:1156
loop_set_status_compat+0x92/0xf0 drivers/block/loop.c:1506
lo_compat_ioctl+0x114/0x140 drivers/block/loop.c:1534
compat_blkdev_ioctl+0x3ba/0x1850 block/compat_ioctl.c:405
C_SYSC_ioctl fs/compat_ioctl.c:1593 [inline]
compat_SyS_ioctl+0x1d7/0x3290 fs/compat_ioctl.c:1540
do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline]
do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391
entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&lo->lo_ctl_mutex#2);
lock(&bdev->bd_mutex);
lock(&lo->lo_ctl_mutex#2);
lock(&bdev->bd_mutex);
*** DEADLOCK ***
1 lock held by syzkaller821047/2981:
#0: (&lo->lo_ctl_mutex#2){+.+.}, at: [<ffffffff83541ef9>] lo_compat_ioctl+0x109/0x140 drivers/block/loop.c:1533
stack backtrace:
CPU: 0 PID: 2981 Comm: syzkaller821047 Not tainted 4.14.0-rc2+ #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:16 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:52
print_circular_bug+0x503/0x710 kernel/locking/lockdep.c:1259
check_prev_add+0x865/0x1520 kernel/locking/lockdep.c:1894
check_prevs_add kernel/locking/lockdep.c:2020 [inline]
validate_chain kernel/locking/lockdep.c:2469 [inline]
__lock_acquire+0x328f/0x4620 kernel/locking/lockdep.c:3498
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0x16f/0x19d0 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
blkdev_reread_part+0x1e/0x40 block/ioctl.c:192
loop_reread_partitions+0x12f/0x1a0 drivers/block/loop.c:614
loop_set_status+0x9ba/0xf60 drivers/block/loop.c:1156
loop_set_status_compat+0x92/0xf0 drivers/block/loop.c:1506
lo_compat_ioctl+0x114/0x140 drivers/block/loop.c:1534
compat_blkdev_ioctl+0x3ba/0x1850 block/compat_ioctl.c:405
C_SYSC_ioctl fs/compat_ioctl.c:1593 [inline]
compat_SyS_ioctl+0x1d7/0x3290 fs/compat_ioctl.c:1540
do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline]
do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391
entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124
RIP: 0023:0xf7f4bc79
RSP: 002b:00000000ff90868c EFLAGS: 00000286 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000004c02
RDX: 00000