====================================================== WARNING: possible circular locking dependency detected kobject: 'loop4' (0000000063e10a85): kobject_uevent_env 4.20.0+ #294 Not tainted ------------------------------------------------------ syz-executor0/22268 is trying to acquire lock: 00000000892ef6da (&bdev->bd_mutex){+.+.}, at: blkdev_reread_part+0x1e/0x40 block/ioctl.c:192 but task is already holding lock: 0000000044815bcb (&lo->lo_ctl_mutex#2){+.+.}, at: lo_compat_ioctl+0x11b/0x170 drivers/block/loop.c:1591 ------------[ cut here ]------------ which lock already depends on the new lock. downgrading a read lock WARNING: CPU: 1 PID: 22272 at kernel/locking/lockdep.c:3553 __lock_downgrade kernel/locking/lockdep.c:3553 [inline] WARNING: CPU: 1 PID: 22272 at kernel/locking/lockdep.c:3553 lock_downgrade+0x4d7/0x900 kernel/locking/lockdep.c:3816 the existing dependency chain (in reverse order) is: Kernel panic - not syncing: panic_on_warn set ... -> #2 (&lo->lo_ctl_mutex#2){+.+.}: CPU: 1 PID: 22272 Comm: blkid Not tainted 4.20.0+ #294 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x166/0x1700 kernel/locking/mutex.c:1072 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 Call Trace: __lo_release drivers/block/loop.c:1650 [inline] lo_release+0xa3/0x1f0 drivers/block/loop.c:1674 __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1d3/0x2c6 lib/dump_stack.c:113 __blkdev_put+0x4f6/0x830 fs/block_dev.c:1796 blkdev_put+0x98/0x540 fs/block_dev.c:1858 panic+0x2ad/0x55c kernel/panic.c:188 blkdev_close+0x8b/0xb0 fs/block_dev.c:1865 __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 __warn.cold.8+0x20/0x45 kernel/panic.c:540 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 report_bug+0x254/0x2d0 lib/bug.c:186 -> #1 (loop_index_mutex){+.+.}: fixup_bug arch/x86/kernel/traps.c:178 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x166/0x1700 kernel/locking/mutex.c:1072 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 lo_open+0x1b/0xb0 drivers/block/loop.c:1630 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973 __blkdev_get+0x360/0x13c0 fs/block_dev.c:1482 RIP: 0010:__lock_downgrade kernel/locking/lockdep.c:3553 [inline] RIP: 0010:lock_downgrade+0x4d7/0x900 kernel/locking/lockdep.c:3816 blkdev_get+0xc1/0xb50 fs/block_dev.c:1617 Code: 00 00 fc ff df 41 c6 44 05 00 f8 e9 1b ff ff ff 48 c7 c7 00 79 4b 88 4c 89 9d 58 ff ff ff 48 89 85 60 ff ff ff e8 d9 20 e7 ff <0f> 0b 48 8b 85 60 ff ff ff 4c 8d 4d d8 4c 89 e9 48 ba 00 00 00 00 blkdev_open+0x1fb/0x280 fs/block_dev.c:1775 RSP: 0018:ffff888056b0fb70 EFLAGS: 00010086 do_dentry_open+0x499/0x1250 fs/open.c:771 RAX: 0000000000000000 RBX: 1ffff1100ad61f74 RCX: 0000000000000000 vfs_open+0xa0/0xd0 fs/open.c:880 RDX: 0000000000000000 RSI: ffffffff8165c255 RDI: 0000000000000006 do_last fs/namei.c:3418 [inline] path_openat+0x12bc/0x5160 fs/namei.c:3534 RBP: ffff888056b0fc28 R08: ffff88805eb3e5c0 R09: fffffbfff12f2330 do_filp_open+0x255/0x380 fs/namei.c:3564 R10: fffffbfff12f2330 R11: ffffffff89791983 R12: ffffffff8b30a920 do_sys_open+0x568/0x700 fs/open.c:1063 R13: ffff888056b0fbc0 R14: 0000000000000001 R15: ffff88805eb3e5c0 __do_sys_open fs/open.c:1081 [inline] __se_sys_open fs/open.c:1076 [inline] __x64_sys_open+0x7e/0xc0 fs/open.c:1076 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&bdev->bd_mutex){+.+.}: lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3841 downgrade_write+0x76/0x270 kernel/locking/rwsem.c:147 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x166/0x1700 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 blkdev_reread_part+0x1e/0x40 block/ioctl.c:192 loop_reread_partitions+0x163/0x190 drivers/block/loop.c:644 loop_set_status+0xb95/0x1010 drivers/block/loop.c:1198 __do_munmap+0xcb0/0xf50 mm/mmap.c:2823 loop_set_status_compat+0xa4/0xf0 drivers/block/loop.c:1563 __vm_munmap+0x138/0x1f0 mm/mmap.c:2848 lo_compat_ioctl+0x13a/0x170 drivers/block/loop.c:1593 compat_blkdev_ioctl+0x3ca/0x1b30 block/compat_ioctl.c:406 __do_compat_sys_ioctl fs/compat_ioctl.c:1052 [inline] __se_compat_sys_ioctl fs/compat_ioctl.c:998 [inline] __ia32_compat_sys_ioctl+0x20e/0x630 fs/compat_ioctl.c:998 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline] do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397 __do_sys_munmap mm/mmap.c:2873 [inline] __se_sys_munmap mm/mmap.c:2870 [inline] __x64_sys_munmap+0x65/0x80 mm/mmap.c:2870 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 other info that might help us debug this: Chain exists of: &bdev->bd_mutex --> loop_index_mutex --> &lo->lo_ctl_mutex#2 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&lo->lo_ctl_mutex#2); lock(loop_index_mutex); entry_SYSCALL_64_after_hwframe+0x49/0xbe lock(&lo->lo_ctl_mutex#2); RIP: 0033:0x7f3f16001417 lock(&bdev->bd_mutex); Code: f0 ff ff 73 01 c3 48 8d 0d 8a ad 20 00 31 d2 48 29 c2 89 11 48 83 c8 ff eb eb 90 90 90 90 90 90 90 90 90 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8d 0d 5d ad 20 00 31 d2 48 29 c2 89 *** DEADLOCK *** RSP: 002b:00007ffc3aa134b8 EFLAGS: 00000203 ORIG_RAX: 000000000000000b 1 lock held by syz-executor0/22268: RAX: ffffffffffffffda RBX: 00007f3f1620c1c8 RCX: 00007f3f16001417 #0: 0000000044815bcb (&lo->lo_ctl_mutex#2){+.+.}, at: lo_compat_ioctl+0x11b/0x170 drivers/block/loop.c:1591 RDX: 0000000000101100 RSI: 00000000000033ef RDI: 00007f3f16204000 stack backtrace: RBP: 00007ffc3aa13620 R08: 0000000000000001 R09: 0000000000000007 R10: 00007f3f15ffba0b R11: 0000000000000203 R12: 00000000ed5abd64 R13: 00000208ed5abd64 R14: 00000208ed4c528e R15: 00007f3f16201740 CPU: 0 PID: 22268 Comm: syz-executor0 Not tainted 4.20.0+ #294 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+0x1d3/0x2c6 lib/dump_stack.c:113 print_circular_bug.isra.34.cold.56+0x1bd/0x27d kernel/locking/lockdep.c:1224 check_prev_add kernel/locking/lockdep.c:1866 [inline] check_prevs_add kernel/locking/lockdep.c:1979 [inline] validate_chain kernel/locking/lockdep.c:2350 [inline] __lock_acquire+0x3360/0x4c20 kernel/locking/lockdep.c:3338 lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3841 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x166/0x1700 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 blkdev_reread_part+0x1e/0x40 block/ioctl.c:192 loop_reread_partitions+0x163/0x190 drivers/block/loop.c:644 loop_set_status+0xb95/0x1010 drivers/block/loop.c:1198 loop_set_status_compat+0xa4/0xf0 drivers/block/loop.c:1563 lo_compat_ioctl+0x13a/0x170 drivers/block/loop.c:1593 compat_blkdev_ioctl+0x3ca/0x1b30 block/compat_ioctl.c:406 __do_compat_sys_ioctl fs/compat_ioctl.c:1052 [inline] __se_compat_sys_ioctl fs/compat_ioctl.c:998 [inline] __ia32_compat_sys_ioctl+0x20e/0x630 fs/compat_ioctl.c:998 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 RIP: 0023:0xf7f57849 Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 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:00000000f5f530cc EFLAGS: 00000296 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000004c02 RDX: 0000000020000500 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Kernel Offset: disabled Rebooting in 86400 seconds..