INFO: task syz-executor.3:2137 blocked for more than 140 seconds. Not tainted 4.9.170+ #47 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D25528 2137 2125 0x00000000 ffff8801cfbf8000 0000000000000000 ffff8801db721000 ffff8801da6b2f80 ffff8801db721018 ffff8801a854f988 ffffffff8280185e ffffffff828113fa 0000000000000001 00ffffff84328f08 ffff8801db7218f0 1ffff100350a9f20 Call Trace: [<000000002549eaa9>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000f57cbe49>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000245f0008>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000245f0008>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<000000002a23dd3c>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 [<000000002c2cdfac>] loop_reread_partitions+0x7c/0x90 drivers/block/loop.c:638 [<00000000567adffe>] loop_clr_fd+0x7dd/0xa60 drivers/block/loop.c:1082 [<0000000086b04630>] lo_ioctl+0x7b6/0x1a10 drivers/block/loop.c:1415 [<0000000092fe73ed>] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [<0000000092fe73ed>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590 [<00000000197a1d21>] block_ioctl+0xde/0x120 fs/block_dev.c:1696 [<0000000018988104>] vfs_ioctl fs/ioctl.c:43 [inline] [<0000000018988104>] file_ioctl fs/ioctl.c:493 [inline] [<0000000018988104>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<0000000063a6eca2>] SYSC_ioctl fs/ioctl.c:694 [inline] [<0000000063a6eca2>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<0000000029887dfc>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<000000003a1bdc67>] 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: [<0000000024129657>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<0000000024129657>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<00000000b12277f8>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 1 lock held by rsyslogd/1912: #0: (&f->f_pos_lock){+.+.+.}, at: [<000000002cde1cf3>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2040: #0: (&tty->ldisc_sem){++++++}, at: [<000000002aa414f9>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [<0000000083fd4b88>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.3/2137: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000004d94d606>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000002a23dd3c>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by syz-executor.0/5450: #0: (&tty->ldisc_sem){++++++}, at: [<000000002aa414f9>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [<0000000083fd4b88>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 3 locks held by syz-executor.5/16819: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000b5acd393>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<0000000050fb3554>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<00000000c3697123>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<00000000c3697123>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 1 lock held by blkid/20385: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000a7659ceb>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by blkid/20386: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000a7659ceb>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000032974187>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.170+ #47 ffff8801d98d7cc8 ffffffff81b4fb21 0000000000000000 0000000000000000 0000000000000000 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5adbc 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<000000005ecdf54c>] __dump_stack lib/dump_stack.c:15 [inline] [<000000005ecdf54c>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000a4d3c061>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000dec87c07>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000001e283b40>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000002e373a93>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000002e373a93>] check_hung_task kernel/hung_task.c:126 [inline] [<000000002e373a93>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<000000002e373a93>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<0000000027863d4e>] kthread+0x278/0x310 kernel/kthread.c:211 [<000000001fac9ac3>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff828108d2