INFO: task syz-executor.5:2095 blocked for more than 140 seconds. Not tainted 4.9.169+ #41 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D25528 2095 1 0x00000004 ffff8801cf8e0000 ffff8801d3bc0b00 ffff8801db621000 ffff8801d3abdf00 ffff8801db621018 ffff8801ac80f988 ffffffff8280152e ffffffff828110ca 0000000000000000 00ffffff842a76c8 ffff8801db6218f0 1ffff10035901f20 Call Trace: [<00000000c2e2cd96>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000a1fa4e4c>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<0000000017813f6d>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<0000000017813f6d>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000440524d0>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 [<000000004495e470>] loop_reread_partitions+0x7c/0x90 drivers/block/loop.c:638 [<000000005d9e764a>] loop_clr_fd+0x7dd/0xa60 drivers/block/loop.c:1082 [<00000000e5c2223d>] lo_ioctl+0x7b6/0x1a10 drivers/block/loop.c:1415 [<00000000909bd6be>] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [<00000000909bd6be>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590 [<000000001e2235b9>] block_ioctl+0xde/0x120 fs/block_dev.c:1696 [<00000000300c9ea1>] vfs_ioctl fs/ioctl.c:43 [inline] [<00000000300c9ea1>] file_ioctl fs/ioctl.c:493 [inline] [<00000000300c9ea1>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<0000000033d3e173>] SYSC_ioctl fs/ioctl.c:694 [inline] [<0000000033d3e173>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<000000001cd1d67b>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<00000000c8b5a7c6>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Showing all locks held in the system: 2 locks held by khungtaskd/24: #0: (rcu_read_lock){......}, at: [<00000000a18afe8d>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [<00000000a18afe8d>] watchdog+0x13c/0xae0 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [<00000000636053fb>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by getty/2020: #0: (&tty->ldisc_sem){++++++}, at: [<0000000007b9a3a7>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [<0000000050cc8e33>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.5/2095: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000002f4c0844>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000440524d0>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by syz-executor.0/2096: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000fd5baaa1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000898b7d74>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.2/2099: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000fd5baaa1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000898b7d74>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 1 lock held by syz-executor.1/2100: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000fd5baaa1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by syz-executor.3/2102: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000fd5baaa1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000898b7d74>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.4/5556: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000fd5baaa1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000898b7d74>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 1 lock held by blkid/10076: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000447d35ff>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 3 locks held by blkid/10077: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000ae8998a6>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<0000000039d8033b>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<00000000c50c6370>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<00000000c50c6370>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 2 locks held by blkid/10082: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000fd5baaa1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000898b7d74>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.169+ #41 ffff8801d98d7cc8 ffffffff81b4f7f1 0000000000000001 0000000000000000 0000000000000001 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5aa8c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<0000000000204166>] __dump_stack lib/dump_stack.c:15 [inline] [<0000000000204166>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<0000000070975d79>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<000000000a527313>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000002615c98d>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000140bb66d>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000140bb66d>] check_hung_task kernel/hung_task.c:125 [inline] [<00000000140bb66d>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [<00000000140bb66d>] watchdog+0x661/0xae0 kernel/hung_task.c:239 [<00000000afb68600>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000f8f25756>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff828105a2