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 '10.128.0.11' (ECDSA) to the list of known hosts. 2018/04/14 14:31:21 parsed 1 programs 2018/04/14 14:31:21 executed programs: 0 syzkaller login: [ 20.306552] IPVS: Creating netns size=2536 id=1 [ 20.441841] [ 20.443505] ====================================================== [ 20.449802] [ INFO: possible circular locking dependency detected ] [ 20.456188] 4.9.93-g2ba4887 #2 Not tainted [ 20.460403] ------------------------------------------------------- [ 20.466790] syz-executor0/3747 is trying to acquire lock: [ 20.472394] (&bdev->bd_mutex){+.+.+.}, at: [] blkdev_reread_part+0x1e/0x40 [ 20.481431] but task is already holding lock: [ 20.486347] (&lo->lo_ctl_mutex#2){+.+.+.}, at: [] lo_compat_ioctl+0x110/0x140 [ 20.496938] which lock already depends on the new lock. [ 20.496938] [ 20.503956] [ 20.503956] the existing dependency chain (in reverse order) is: [ 20.511561] -> #2 (&lo->lo_ctl_mutex#2){+.+.+.}: [ 20.517116] lock_acquire+0x130/0x3e0 [ 20.521426] mutex_lock_nested+0xc0/0x870 [ 20.526083] lo_release+0x85/0x160 [ 20.530130] __blkdev_put+0x636/0x840 [ 20.534430] blkdev_put+0x85/0x560 [ 20.538472] blkdev_close+0x8b/0xb0 [ 20.543427] __fput+0x263/0x700 [ 20.547214] ____fput+0x15/0x20 [ 20.550999] task_work_run+0x10c/0x180 [ 20.555389] exit_to_usermode_loop+0xfc/0x120 [ 20.560397] do_syscall_64+0x364/0x490 [ 20.565051] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 20.570654] -> #1 (loop_index_mutex){+.+.+.}: [ 20.576018] lock_acquire+0x130/0x3e0 [ 20.581622] mutex_lock_nested+0xc0/0x870 [ 20.586626] lo_open+0x1b/0xa0 [ 20.590582] __blkdev_get+0x263/0xd60 [ 20.594878] blkdev_get+0x2da/0x920 [ 20.599000] blkdev_open+0x1a5/0x250 [ 20.603218] do_dentry_open+0x703/0xc80 [ 20.607686] vfs_open+0x11c/0x210 [ 20.611643] path_openat+0x758/0x3590 [ 20.615946] do_filp_open+0x197/0x270 [ 20.620245] do_sys_open+0x30d/0x5c0 [ 20.624452] SyS_open+0x2d/0x40 [ 20.628231] do_syscall_64+0x1a6/0x490 [ 20.632618] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 20.638218] -> #0 (&bdev->bd_mutex){+.+.+.}: [ 20.643621] __lock_acquire+0x3019/0x4070 [ 20.649332] lock_acquire+0x130/0x3e0 [ 20.653735] mutex_lock_nested+0xc0/0x870 [ 20.658553] blkdev_reread_part+0x1e/0x40 [ 20.663203] loop_reread_partitions+0x7c/0x90 [ 20.668468] loop_set_status+0x9c7/0xfc0 [ 20.673120] loop_set_status_compat+0x9a/0xf0 [ 20.678107] lo_compat_ioctl+0x11b/0x140 [ 20.682834] compat_blkdev_ioctl+0x3a5/0x3ad0 [ 20.687912] compat_SyS_ioctl+0x126/0x1fe0 [ 20.692914] do_fast_syscall_32+0x2f7/0x870 [ 20.698668] entry_SYSENTER_compat+0x90/0xa2 [ 20.703575] [ 20.703575] other info that might help us debug this: [ 20.703575] [ 20.711947] Chain exists of: &bdev->bd_mutex --> loop_index_mutex --> &lo->lo_ctl_mutex#2 [ 20.721506] Possible unsafe locking scenario: [ 20.721506] [ 20.728095] CPU0 CPU1 [ 20.732819] ---- ---- [ 20.737496] lock(&lo->lo_ctl_mutex#2); [ 20.742147] lock(loop_index_mutex); [ 20.750202] lock(&lo->lo_ctl_mutex#2); [ 20.757207] lock(&bdev->bd_mutex); [ 20.761221] [ 20.761221] *** DEADLOCK *** [ 20.761221] [ 20.767261] 1 lock held by syz-executor0/3747: [ 20.771919] #0: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [] lo_compat_ioctl+0x110/0x140 [ 20.782079] [ 20.782079] stack backtrace: [ 20.786726] CPU: 0 PID: 3747 Comm: syz-executor0 Not tainted 4.9.93-g2ba4887 #2 [ 20.794150] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 20.804121] ffff8801bbbef788 ffffffff81d9aa29 ffffffff8538b820 ffffffff853b5610 [ 20.812179] ffffffff8538ac50 ffff8801bd3c08e0 ffff8801bd3c0000 ffff8801bbbef7d0 [ 20.820285] ffffffff8142399d 0000000000000001 00000000bd3c0000 0000000000000001 [ 20.828396] Call Trace: [ 20.830957] [] dump_stack+0xc1/0x128 [ 20.836296] [] print_circular_bug.cold.51+0x1bd/0x27d [ 20.843109] [] __lock_acquire+0x3019/0x4070 [ 20.849320] [] ? save_stack_trace+0x16/0x20 [ 20.856144] [] ? save_stack+0x43/0xd0 [ 20.861575] [] ? kasan_slab_free+0x72/0xc0 [ 20.867455] [] ? debug_check_no_locks_freed+0x210/0x210 [ 20.874446] [] ? __lock_acquire+0x654/0x4070 [ 20.880480] [] ? __lock_is_held+0xa2/0xf0 [ 20.886255] [] lock_acquire+0x130/0x3e0 [ 20.891857] [] ? blkdev_reread_part+0x1e/0x40 [ 20.897977] [] ? blkdev_reread_part+0x1e/0x40 [ 20.904100] [] mutex_lock_nested+0xc0/0x870 [ 20.910044] [] ? blkdev_reread_part+0x1e/0x40 [ 20.916163] [] ? mutex_trylock+0x3e0/0x3e0 [ 20.923396] [] ? _raw_spin_unlock_irqrestore+0x5a/0x70 [ 20.930312] [] ? trace_hardirqs_on_caller+0x38b/0x590 [ 20.937132] [] blkdev_reread_part+0x1e/0x40 [ 20.943088] [] loop_reread_partitions+0x7c/0x90 [ 20.949378] [] loop_set_status+0x9c7/0xfc0 [ 20.955243] [] loop_set_status_compat+0x9a/0xf0 [ 20.961541] [] ? loop_set_status+0xfc0/0xfc0 [ 20.969268] [] lo_compat_ioctl+0x11b/0x140 [ 20.975135] [] ? lo_ioctl+0x1aa0/0x1aa0 [ 20.980749] [] compat_blkdev_ioctl+0x3a5/0x3ad0 [ 20.987047] [] ? debug_check_no_obj_freed+0x2ec/0x930 [ 20.993955] [] ? cfq_dispatch_requests+0x2ef0/0x2ef0 [ 21.000696] [] ? compat_SyS_futex+0x1e1/0x2f0 [ 21.006821] [] ? security_file_ioctl+0x8f/0xc0 [ 21.014999] [] compat_SyS_ioctl+0x126/0x1fe0 [ 21.021032] [] ? cfq_dispatch_requests+0x2ef0/0x2ef0 [ 21.027767] [] ? do_ioctl+0x60/0x60 [ 21.033039] [] do_fast_syscall_32+0x2f7/0x870 [ 21.039156] [] ? trace_hardirqs_off_thunk+0x1a/0x1