INFO: task syz-executor.5:2113 blocked for more than 140 seconds. Not tainted 4.4.174+ #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D ffff8801c6b6faf8 25248 2113 1 0x00000004 ffff8801c6b6faf8 ffff8801d4b00000 8fb0261ac6d2a1e7 ffff8801d4b00000 0000000000000002 ffff8801d4b00800 ffff8801db61f180 ffff8801db61f1a8 ffff8801db61e898 ffff880000215f00 ffff8801d4b00000 ffffed0038d6d001 Call Trace: [] schedule+0x99/0x1d0 kernel/sched/core.c:3355 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621 [] __lo_release drivers/block/loop.c:1653 [inline] [] lo_release+0x84/0x1b0 drivers/block/loop.c:1676 [] __blkdev_put+0x461/0x840 fs/block_dev.c:1535 [] blkdev_put+0x88/0x560 fs/block_dev.c:1600 [] blkdev_close+0x8b/0xb0 fs/block_dev.c:1607 [] __fput+0x246/0x710 fs/file_table.c:208 [] ____fput+0x16/0x20 fs/file_table.c:244 [] task_work_run+0x202/0x2b0 kernel/task_work.c:115 [] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [] exit_to_usermode_loop+0x14a/0x170 arch/x86/entry/common.c:188 [] prepare_exit_to_usermode arch/x86/entry/common.c:221 [inline] [] syscall_return_slowpath+0x25b/0x2e0 arch/x86/entry/common.c:286 [] int_ret_from_sys_call+0x25/0xa3 3 locks held by syz-executor.5/2113: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_put+0xbb/0x840 fs/block_dev.c:1516 #1: (loop_index_mutex){+.+.+.}, at: [] lo_release+0x1e/0x1b0 drivers/block/loop.c:1675 #2: (loop_ctl_mutex#2){+.+.+.}, at: [] __lo_release drivers/block/loop.c:1653 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [] lo_release+0x84/0x1b0 drivers/block/loop.c:1676 Sending NMI to all CPUs: NMI backtrace for cpu 0 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.174+ #4 task: ffffffff82e151c0 task.stack: ffffffff82e00000 RIP: 0010:[] [] native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:53 RSP: 0018:ffffffff82e07db0 EFLAGS: 00000246 RAX: 0000000000000007 RBX: ffffffff8319bf68 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff82e15a84 RBP: ffffffff82e07de0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffffffff82e08000 R14: dffffc0000000000 R15: ffffffff82e00000 FS: 0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fc01f11a000 CR3: 00000000b9231000 CR4: 00000000001606b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 Stack: ffffffff81020b16 ffffffff82e00000 0000000000000000 ffffffff82e08000 dffffc0000000000 ffffffff82e00000 ffffffff82e07df0 ffffffff81022d50 ffffffff82e07e08 ffffffff811eb4c8 0000000000000000 ffffffff82e07ed0 Call Trace: [] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:423 [] default_idle_call+0x48/0x70 kernel/sched/idle.c:93 [] cpuidle_idle_call kernel/sched/idle.c:157 [inline] [] cpu_idle_loop kernel/sched/idle.c:253 [inline] [] cpu_startup_entry+0x6d1/0x810 kernel/sched/idle.c:301 [] rest_init+0x190/0x199 init/main.c:410 [] start_kernel+0x64a/0x67e init/main.c:682 [] x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:196 [] x86_64_start_kernel+0x137/0x15a arch/x86/kernel/head64.c:185 Code: 2e 0f 1f 84 00 00 00 00 00 fa c3 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 fb c3 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 fb f4 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 f4 c3 0f 1f 40 00 66 NMI backtrace for cpu 1 CPU: 1 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4 task: ffff8801da7d97c0 task.stack: ffff8800001d0000 RIP: 0010:[] [] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:62 [inline] RIP: 0010:[] [] flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69 RSP: 0018:ffff8800001d7c88 EFLAGS: 00000046 RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000 RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300 RBP: ffff8800001d7cb8 R08: 0000000000000018 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246 R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002 FS: 0000000000000000(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f29245ca000 CR3: 00000000b9231000 CR4: 00000000001606b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34 000000000001b6c0 0000000000000008 ffff8800001d7cd8 ffffffff81092bee 0000000000000008 ffffffff82924260 ffff8800001d7d30 ffffffff81ab8252 Call Trace: [] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33 [] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae lib/nmi_backtrace.c:85 [] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 [] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog.cold+0xd3/0xee kernel/hung_task.c:238 [] kthread+0x273/0x310 kernel/kthread.c:211 [] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537 Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00 02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1