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 '10.128.0.51' (ECDSA) to the list of known hosts. 2018/04/13 01:54:06 parsed 1 programs 2018/04/13 01:54:06 executed programs: 0 syzkaller login: [ 27.186181] IPVS: Creating netns size=2536 id=1 [ 27.314471] [ 27.316149] ====================================================== [ 27.322443] [ INFO: possible circular locking dependency detected ] [ 27.328825] 4.9.93-gf6bec4e #1 Not tainted [ 27.333034] ------------------------------------------------------- [ 27.339416] syz-executor0/3783 is trying to acquire lock: [ 27.344926] (&bdev->bd_mutex){+.+.+.}, at: [] blkdev_reread_part+0x1e/0x40 [ 27.353936] but task is already holding lock: [ 27.358578] (&lo->lo_ctl_mutex#2){+.+.+.}, at: [] lo_compat_ioctl+0x110/0x140 [ 27.367981] which lock already depends on the new lock. [ 27.367981] [ 27.374969] [ 27.374969] the existing dependency chain (in reverse order) is: [ 27.382567] -> #2 (&lo->lo_ctl_mutex#2){+.+.+.}: [ 27.388181] lock_acquire+0x130/0x3e0 [ 27.392495] mutex_lock_nested+0xc0/0x870 [ 27.397144] lo_release+0x85/0x160 [ 27.401191] __blkdev_put+0x636/0x840 [ 27.405496] blkdev_put+0x85/0x560 [ 27.409532] blkdev_close+0x8b/0xb0 [ 27.413657] __fput+0x263/0x700 [ 27.417436] ____fput+0x15/0x20 [ 27.421212] task_work_run+0x10c/0x180 [ 27.425600] exit_to_usermode_loop+0xfc/0x120 [ 27.430593] do_syscall_64+0x364/0x490 [ 27.434979] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.440577] -> #1 (loop_index_mutex){+.+.+.}: [ 27.445735] lock_acquire+0x130/0x3e0 [ 27.450034] mutex_lock_nested+0xc0/0x870 [ 27.454679] lo_open+0x1b/0xa0 [ 27.458368] __blkdev_get+0x263/0xd60 [ 27.462666] blkdev_get+0x2da/0x920 [ 27.466787] blkdev_open+0x1a5/0x250 [ 27.470997] do_dentry_open+0x703/0xc80 [ 27.475469] vfs_open+0x11c/0x210 [ 27.479421] path_openat+0x758/0x3590 [ 27.483715] do_filp_open+0x197/0x270 [ 27.488011] do_sys_open+0x310/0x5c0 [ 27.492220] SyS_open+0x2d/0x40 [ 27.495999] do_syscall_64+0x1a6/0x490 [ 27.500382] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.505977] -> #0 (&bdev->bd_mutex){+.+.+.}: [ 27.511029] __lock_acquire+0x301c/0x4080 [ 27.515675] lock_acquire+0x130/0x3e0 [ 27.519972] mutex_lock_nested+0xc0/0x870 [ 27.524627] blkdev_reread_part+0x1e/0x40 [ 27.529829] loop_reread_partitions+0x7c/0x90 [ 27.534820] loop_set_status+0x9c7/0xfc0 [ 27.539378] loop_set_status_compat+0x9a/0xf0 [ 27.544372] lo_compat_ioctl+0x11b/0x140 [ 27.548938] compat_blkdev_ioctl+0x3a5/0x3ad0 [ 27.553932] compat_SyS_ioctl+0x126/0x1fe0 [ 27.558669] do_fast_syscall_32+0x2f7/0x870 [ 27.563495] entry_SYSENTER_compat+0x90/0xa2 [ 27.568397] [ 27.568397] other info that might help us debug this: [ 27.568397] [ 27.576518] Chain exists of: &bdev->bd_mutex --> loop_index_mutex --> &lo->lo_ctl_mutex#2 [ 27.586139] Possible unsafe locking scenario: [ 27.586139] [ 27.592171] CPU0 CPU1 [ 27.596816] ---- ---- [ 27.601471] lock(&lo->lo_ctl_mutex#2); [ 27.605901] lock(loop_index_mutex); [ 27.612470] lock(&lo->lo_ctl_mutex#2); [ 27.619384] lock(&bdev->bd_mutex); [ 27.623327] [ 27.623327] *** DEADLOCK *** [ 27.623327] [ 27.629367] 1 lock held by syz-executor0/3783: [ 27.633921] #0: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [] lo_compat_ioctl+0x110/0x140 [ 27.643889] [ 27.643889] stack backtrace: [ 27.648364] CPU: 1 PID: 3783 Comm: syz-executor0 Not tainted 4.9.93-gf6bec4e #1 [ 27.655784] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.665119] ffff8801b6b97788 ffffffff81d9c299 ffffffff8538b670 ffffffff853b5b20 [ 27.673147] ffffffff8538aaa0 ffff8801b82f20e0 ffff8801b82f1800 ffff8801b6b977d0 [ 27.681159] ffffffff814241ad 0000000000000001 00000000b82f1800 0000000000000001 [ 27.689166] Call Trace: [ 27.691735] [] dump_stack+0xc1/0x128 [ 27.697077] [] print_circular_bug.cold.51+0x1bd/0x27d [ 27.703896] [] __lock_acquire+0x301c/0x4080 [ 27.709846] [] ? save_stack_trace+0x16/0x20 [ 27.715799] [] ? save_stack+0x43/0xd0 [ 27.721236] [] ? kasan_slab_free+0x72/0xc0 [ 27.727100] [] ? debug_check_no_locks_freed+0x210/0x210 [ 27.734099] [] ? __lock_acquire+0x654/0x4080 [ 27.740139] [] ? __lock_is_held+0xa2/0xf0 [ 27.745925] [] lock_acquire+0x130/0x3e0 [ 27.751530] [] ? blkdev_reread_part+0x1e/0x40 [ 27.757656] [] ? blkdev_reread_part+0x1e/0x40 [ 27.763780] [] mutex_lock_nested+0xc0/0x870 [ 27.769733] [] ? blkdev_reread_part+0x1e/0x40 [ 27.775862] [] ? mutex_trylock+0x3e0/0x3e0 [ 27.781733] [] ? _raw_spin_unlock_irqrestore+0x5a/0x70 [ 27.788643] [] ? trace_hardirqs_on_caller+0x38b/0x590 [ 27.795465] [] blkdev_reread_part+0x1e/0x40 [ 27.801414] [] loop_reread_partitions+0x7c/0x90 [ 27.807713] [] loop_set_status+0x9c7/0xfc0 [ 27.813577] [] loop_set_status_compat+0x9a/0xf0 [ 27.819871] [] ? loop_set_status+0xfc0/0xfc0 [ 27.825907] [] lo_compat_ioctl+0x11b/0x140 [ 27.831766] [] ? lo_ioctl+0x1aa0/0x1aa0 [ 27.837372] [] compat_blkdev_ioctl+0x3a5/0x3ad0 [ 27.843671] [] ? cfq_dispatch_requests+0x2ef0/0x2ef0 [ 27.850404] [] ? compat_SyS_futex+0x1e1/0x2f0 [ 27.856529] [] ? security_file_ioctl+0x8f/0xc0 [ 27.862740] [] compat_SyS_