INIT: Entering runlevel: 2 [info] Using makefile-style concurrent boot in runlevel 2. [....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added 'ci-upstream-kasan-gce-386-2,10.128.0.31' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 41.635459] [ 41.637099] ====================================================== [ 41.643380] WARNING: possible circular locking dependency detected [ 41.649662] 4.14.0-rc2+ #10 Not tainted [ 41.653596] ------------------------------------------------------ [ 41.659880] syzkaller821047/2981 is trying to acquire lock: [ 41.665550] (&bdev->bd_mutex){+.+.}, at: [] blkdev_reread_part+0x1e/0x40 [ 41.674016] [ 41.674016] but task is already holding lock: [ 41.679950] (&lo->lo_ctl_mutex#2){+.+.}, at: [] lo_compat_ioctl+0x109/0x140 [ 41.688671] [ 41.688671] which lock already depends on the new lock. [ 41.688671] [ 41.696955] [ 41.696955] the existing dependency chain (in reverse order) is: [ 41.704537] [ 41.704537] -> #1 (&lo->lo_ctl_mutex#2){+.+.}: [ 41.710568] __lock_acquire+0x328f/0x4620 [ 41.715200] lock_acquire+0x1d5/0x580 [ 41.719485] __mutex_lock+0x16f/0x19d0 [ 41.723856] mutex_lock_nested+0x16/0x20 [ 41.728404] lo_release+0x6b/0x180 [ 41.732429] __blkdev_put+0x602/0x7c0 [ 41.736712] blkdev_put+0x85/0x4f0 [ 41.740735] blkdev_close+0x91/0xc0 [ 41.744847] __fput+0x333/0x7f0 [ 41.748610] ____fput+0x15/0x20 [ 41.752375] task_work_run+0x199/0x270 [ 41.756746] exit_to_usermode_loop+0x296/0x310 [ 41.761812] syscall_return_slowpath+0x42f/0x510 [ 41.767052] entry_SYSCALL_64_fastpath+0xbc/0xbe [ 41.772288] [ 41.772288] -> #0 (&bdev->bd_mutex){+.+.}: [ 41.777975] check_prev_add+0x865/0x1520 [ 41.782520] __lock_acquire+0x328f/0x4620 [ 41.787150] lock_acquire+0x1d5/0x580 [ 41.791434] __mutex_lock+0x16f/0x19d0 [ 41.795805] mutex_lock_nested+0x16/0x20 [ 41.800352] blkdev_reread_part+0x1e/0x40 [ 41.804988] loop_reread_partitions+0x12f/0x1a0 [ 41.810139] loop_set_status+0x9ba/0xf60 [ 41.814687] loop_set_status_compat+0x92/0xf0 [ 41.819665] lo_compat_ioctl+0x114/0x140 [ 41.824211] compat_blkdev_ioctl+0x3ba/0x1850 [ 41.829192] compat_SyS_ioctl+0x1d7/0x3290 [ 41.833911] do_fast_syscall_32+0x3f2/0xf05 [ 41.838719] entry_SYSENTER_compat+0x51/0x60 [ 41.843607] [ 41.843607] other info that might help us debug this: [ 41.843607] [ 41.851712] Possible unsafe locking scenario: [ 41.851712] [ 41.857734] CPU0 CPU1 [ 41.862367] ---- ---- [ 41.866997] lock(&lo->lo_ctl_mutex#2); [ 41.871025] lock(&bdev->bd_mutex); [ 41.877220] lock(&lo->lo_ctl_mutex#2); [ 41.883771] lock(&bdev->bd_mutex); [ 41.887445] [ 41.887445] *** DEADLOCK *** [ 41.887445] [ 41.893466] 1 lock held by syzkaller821047/2981: [ 41.898181] #0: (&lo->lo_ctl_mutex#2){+.+.}, at: [] lo_compat_ioctl+0x109/0x140 [ 41.907339] [ 41.907339] stack backtrace: [ 41.911800] CPU: 0 PID: 2981 Comm: syzkaller821047 Not tainted 4.14.0-rc2+ #10 [ 41.919124] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 41.928441] Call Trace: [ 41.930995] dump_stack+0x194/0x257 [ 41.934588] ? arch_local_irq_restore+0x53/0x53 [ 41.939225] print_circular_bug+0x503/0x710 [ 41.943528] ? print_circular_bug_entry+0xb0/0xb0 [ 41.948337] ? __read_once_size_nocheck.constprop.8+0x10/0x10 [ 41.954186] check_prev_add+0x865/0x1520 [ 41.958212] ? copy_trace+0x1d0/0x1d0 [ 41.961978] ? check_usage+0xb70/0xb70 [ 41.965829] ? unwind_next_frame.part.6+0x1ae/0xc70 [ 41.970808] ? unwind_dump+0x4c0/0x4c0 [ 41.974657] ? unwind_dump+0x4c0/0x4c0 [ 41.978511] ? hlock_class+0x140/0x140 [ 41.982362] ? copy_trace+0x1d0/0x1d0 [ 41.986127] __lock_acquire+0x328f/0x4620 [ 41.990246] ? __lock_acquire+0x328f/0x4620 [ 41.994534] ? copy_trace+0x1d0/0x1d0 [ 41.998300] ? debug_check_no_locks_freed+0x3d0/0x3d0 [ 42.003452] ? __read_once_size_nocheck.constprop.8+0x10/0x10 [ 42.009300] ? lo_compat_ioctl+0x114/0x140 [ 42.013498] ? loop_set_status_compat+0x92/0xf0 [ 42.018134] ? unwind_next_frame.part.6+0x1ae/0xc70 [ 42.023115] ? unwind_next_frame.part.6+0x1ae/0xc70 [ 42.028097] ? unwind_dump+0x4c0/0x4c0 [ 42.031955] ? unwind_dump+0x4c0/0x4c0 [ 42.035807] ? __unwind_start+0x169/0x330 [ 42.039921] ? unwind_get_return_address+0x61/0xa0 [ 42.044814] ? __save_stack_trace+0x61/0xd0 [ 42.049101] ? loop_set_status_compat+0x92/0xf0 [ 42.053732] ? save_stack_trace+0x16/0x20 [ 42.057846] ? __lock_acquire+0x732/0x4620 [ 42.062047] ? find_held_lock+0x39/0x1d0 [ 42.066074] ? check_noncircular+0x20/0x20 [ 42.070272] ? find_held_lock+0x39/0x1d0 [ 42.074298] ? check_noncircular+0x20/0x20 [ 42.078497] ? debug_check_no_locks_freed+0x3d0/0x3d0 [ 42.083649] ? debug_check_no_locks_freed+0x3d0/0x3d0 [ 42.088802] ? find_held_lock+0x39/0x1d0 [ 42.092828] lock_acquire+0x1d5/0x580 [ 42.096595] ? blkdev_reread_part+0x1e/0x40 [ 42.100881] ? lock_release+0xd70/0xd70 [ 42.104821] ? check_same_owner+0x320/0x320 [ 42.109105] ? lock_downgrade+0x990/0x990 [ 42.113218] ? __might_sleep+0x95/0x190 [ 42.117154] ? blkdev_reread_part+0x1e/0x40 [ 42.121439] __mutex_lock+0x16f/0x19d0 [ 42.125291] ? blkdev_reread_part+0x1e/0x40 [ 42.129578] ? blkdev_reread_part+0x1e/0x40 [ 42.133869] ? mutex_lock_io_nested+0x1880/0x1880 [ 42.138674] ? check_noncircular+0x20/0x20 [ 42.142875] ? print_usage_bug+0x480/0x480 [ 42.147077] ? depot_save_stack+0x3b5/0x490 [ 42.151369] ? find_held_lock+0x39/0x1d0 [ 42.155398] ? lock_downgrade+0x990/0x990 [ 42.159510] ? cpumask_next+0x24/0x30 [ 42.163275] ? __wake_up_common_lock+0x190/0x310 [ 42.167996] ? percpu_ref_switch_to_atomic_rcu+0x5d0/0x5d0 [ 42.173584] ? do_raw_spin_trylock+0x190/0x190 [ 42.178137] ? mark_held_locks+0xb2/0x100 [ 42.182248] ? _raw_spin_unlock_irqrestore+0x31/0xba [ 42.187315] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 42.192294] ? trace_hardirqs_on+0xd/0x10 [ 42.196404] ? __wake_up_common_lock+0x1c2/0x310 [ 42.201125] mutex_lock_nested+0x16/0x20 [ 42.205150] ? mutex_lock_nested+0x16/0x20 [ 42.209356] blkdev_reread_part+0x1e/0x40 [ 42.213467] loop_reread_partitions+0x12f/0x1a0 [ 42.218098] ? __loop_update_dio+0x640/0x640 [ 42.222472] loop_set_status+0x9ba/0xf60 [ 42.226496] loop_set_status_compat+0x92/0xf0 [ 42.230955] ? loop_set_status+0xf60/0xf60 [ 42.235158] ? selinux_file_ioctl+0x444/0x690 [ 42.239626] lo_compat_ioctl+0x114/0x140 [ 42.243650] ? lo_ioctl+0x1b80/0x1b80 [ 42.247414] compat_blkdev_ioctl+0x3ba/0x1850 [ 42.251875] ? bfq_create_group_hierarchy+0x180/0x180 [ 42.257030] ? security_file_ioctl+0x89/0xb0 [ 42.261403] compat_SyS_ioctl+0x1d7/0x3290 [ 42.265600] ? bfq_create_group_hierarchy+0x180/0x180 [ 42.270754] ? do_ioctl+0x60/0x60 [ 42.274173] ? do_fast_syscall_32+0x158/0xf05 [ 42.278634] ? do_ioctl+0x60/0x60 [ 42.282048] do_fast_syscall_32+0x3f2/0xf05 [ 42.286333] ? do_int80_syscall_32+0x940/0x940 [ 42.290886] ? kasan_check_read+0x11/0x20 [ 42.294997] ? syscall_return_slowpath+0x510/0x510 [ 42.299889] ? SyS_rt_sigaction+0x94/0x1b0 [ 42.304091] ? sysret32_from_system_call+0x5/0x3b [ 42.308899] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 42.313709] entry_SYSENTER_compat+0x51/0x60 [ 42.318081] RIP: 0023:0xf7f4bc79 [ 42.321410] RSP: 002b:00000000ff90868c EFLAGS: 00000286 ORIG_RAX: 0000000000000036 [ 42.329082] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000004c02 [ 42.336314] RDX: 00000