INFO: task syz-executor.1:3023 blocked for more than 140 seconds. Not tainted 4.9.205-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D25544 3023 1 0x00000004 0000000000000083 ffff8801a89f97c0 ffff8801a9379b80 ffff8801db61ffc0 ffff8801d521df00 ffff8801db61ffd8 ffff8801acee7688 ffffffff8280a6ae 0000000041b58ab3 ffffffff82e2ad80 00ffffff81205320 ffff8801db6208b0 Call Trace: [<00000000e521e442>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000522ba665>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<0000000039a16c80>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<0000000039a16c80>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000133b0655>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 [<00000000b3d5482c>] __blkdev_get+0x268/0xeb0 fs/block_dev.c:1287 [<0000000085f74c47>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424 [<00000000ffed691f>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579 [<000000009cc26ca8>] do_dentry_open+0x422/0xd20 fs/open.c:791 [<000000002a063bf0>] vfs_open+0x105/0x230 fs/open.c:904 [<00000000883567cf>] do_last fs/namei.c:3457 [inline] [<00000000883567cf>] path_openat+0xbf5/0x2f60 fs/namei.c:3581 [<00000000db1990db>] do_filp_open+0x1a1/0x280 fs/namei.c:3615 [<0000000079adc170>] do_sys_open+0x2f0/0x610 fs/open.c:1097 [<000000007925c3be>] SYSC_open fs/open.c:1115 [inline] [<000000007925c3be>] SyS_open+0x2d/0x40 fs/open.c:1110 [<0000000060a02751>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<00000000a97f77db>] 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: [<00000000a5b0d5c9>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000a5b0d5c9>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.?..}, at: [<000000005c167a75>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 1 lock held by rsyslogd/1900: #0: (&f->f_pos_lock){+.+.+.}, at: [<00000000d41b7d9d>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2030: #0: (&tty->ldisc_sem){++++++}, at: [<00000000ec4338d4>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [<00000000099c5b0a>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.1/3023: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000009388dd5b>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000133b0655>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.0/8609: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<000000002a4baa1a>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000f4359f23>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by syz-executor.4/8616: #0: (loop_index_mutex){+.+.+.}, at: [<000000007b6f566e>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<00000000b7199ca0>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1988 1 lock held by syz-executor.4/8627: #0: (loop_index_mutex){+.+.+.}, at: [<000000007b6f566e>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 1 lock held by syz-executor.4/8630: #0: (loop_index_mutex){+.+.+.}, at: [<000000007b6f566e>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 1 lock held by syz-executor.3/8618: #0: (loop_index_mutex){+.+.+.}, at: [<000000007b6f566e>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 1 lock held by syz-executor.3/8629: #0: (loop_index_mutex){+.+.+.}, at: [<000000007b6f566e>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 1 lock held by syz-executor.3/8631: #0: (loop_index_mutex){+.+.+.}, at: [<000000007b6f566e>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 2 locks held by blkid/8617: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000009388dd5b>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000133b0655>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.205-syzkaller #0 ffff8801d98d7cc8 ffffffff81b55e6b 0000000000000001 0000000000000000 0000000000000001 ffffffff8109a001 dffffc0000000000 ffff8801d98d7d00 ffffffff81b6110c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<00000000c067ccd3>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000c067ccd3>] dump_stack+0xcb/0x130 lib/dump_stack.c:56 [<00000000f2df14e5>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000da3efcb8>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000a7ebf040>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000130d44e0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000130d44e0>] check_hung_task kernel/hung_task.c:126 [inline] [<00000000130d44e0>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<00000000130d44e0>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<0000000003537271>] kthread+0x278/0x310 kernel/kthread.c:211 [<0000000059043b3e>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff82819801