INFO: task syz-executor.2:18887 blocked for more than 143 seconds. Not tainted 5.6.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D28848 18887 9506 0x00004004 Call Trace: schedule+0xd0/0x2a0 kernel/sched/core.c:4154 schedule_timeout+0x6db/0xba0 kernel/time/timer.c:1871 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x26a/0x3c0 kernel/sched/completion.c:136 flush_workqueue+0x40a/0x14c0 kernel/workqueue.c:2827 nbd_start_device_ioctl drivers/block/nbd.c:1311 [inline] __nbd_ioctl drivers/block/nbd.c:1386 [inline] nbd_ioctl+0x7ae/0xb7c drivers/block/nbd.c:1426 __blkdev_driver_ioctl block/ioctl.c:321 [inline] blkdev_ioctl+0x25b/0x660 block/ioctl.c:717 block_ioctl+0xe9/0x130 fs/block_dev.c:1983 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x11a/0x180 fs/ioctl.c:763 __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl fs/ioctl.c:770 [inline] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c4a9 Code: Bad RIP value. RSP: 002b:00007f326fb7cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f326fb7d6d4 RCX: 000000000045c4a9 RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003 RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000402 R14: 00000000004c6645 R15: 000000000076bfcc Showing all locks held in the system: 1 lock held by khungtaskd/1139: #0: ffffffff897accc0 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5331 1 lock held by rsyslogd/9366: #0: ffff888099ef1b60 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xe3/0x100 fs/file.c:821 2 locks held by getty/9456: #0: ffff8880a3661090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc90001a2b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 2 locks held by getty/9457: #0: ffff8880995c6090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc900019bb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 2 locks held by getty/9458: #0: ffff8880a6b19090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc900019fb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 2 locks held by getty/9459: #0: ffff888099009090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc90001a0b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 2 locks held by getty/9460: #0: ffff888095f4f090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc90001a4b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 2 locks held by getty/9461: #0: ffff888097120090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc90001a3b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 2 locks held by getty/9462: #0: ffff88809ec76090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc9000198b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 2 locks held by kworker/u5:2/11028: #0: ffff888047287d28 ((wq_completion)knbd2-recv){+.+.}, at: __write_once_size include/linux/compiler.h:226 [inline] #0: ffff888047287d28 ((wq_completion)knbd2-recv){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888047287d28 ((wq_completion)knbd2-recv){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:855 [inline] #0: ffff888047287d28 ((wq_completion)knbd2-recv){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:40 [inline] #0: ffff888047287d28 ((wq_completion)knbd2-recv){+.+.}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff888047287d28 ((wq_completion)knbd2-recv){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline] #0: ffff888047287d28 ((wq_completion)knbd2-recv){+.+.}, at: process_one_work+0x82a/0x1690 kernel/workqueue.c:2235 #1: ffffc9000495fdd0 ((work_completion)(&args->work)){+.+.}, at: process_one_work+0x85e/0x1690 kernel/workqueue.c:2239 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1139 Comm: khungtaskd Not tainted 5.6.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x188/0x20d lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x231/0x27e lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline] watchdog+0xa8c/0x1010 kernel/hung_task.c:289 kthread+0x357/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 4330 Comm: udevd Not tainted 5.6.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:ep_poll+0x3b3/0xe60 fs/eventpoll.c:1812 Code: ff ff ff ff ff ff ff 7f e8 ea 68 94 ff 4c 8b 44 24 38 48 89 94 24 c8 00 00 00 48 89 84 24 c0 00 00 00 4c 89 c7 e8 4d 31 f1 ff <4c> 8b bc 24 c0 00 00 00 48 bf 03 7d c1 25 02 00 00 00 48 89 44 24 RSP: 0018:ffffc90001b47cf8 EFLAGS: 00000296 RAX: 00000000002dc6bf RBX: ffff8880a827cc00 RCX: 0000000000000000 RDX: dffffc0000000000 RSI: ffffffff81be5d8b RDI: 0000000000000006 RBP: ffffc90001b47eb0 R08: ffff88809326e3c0 R09: 0000000000000000 R10: ffffed1012704308 R11: 0000000000000000 R12: 1ffff92000368fa9 R13: ffff8880a827cd10 R14: 7fffffffffffffff R15: 0000000000000003 FS: 00007f32eaadb7a0(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000071d6b4 CR3: 00000000a0c3a000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: do_epoll_wait+0x209/0x260 fs/eventpoll.c:2298 __do_sys_epoll_wait fs/eventpoll.c:2308 [inline] __se_sys_epoll_wait fs/eventpoll.c:2305 [inline] __x64_sys_epoll_wait+0x93/0xf0 fs/eventpoll.c:2305 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f32ea1ef943 Code: 00 31 d2 48 29 c2 64 89 11 48 83 c8 ff eb ea 90 90 90 90 90 90 90 90 83 3d b5 dc 2a 00 00 75 13 49 89 ca b8 e8 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 34 c3 48 83 ec 08 e8 3b c4 00 00 48 89 04 24 RSP: 002b:00007ffff15b0d08 EFLAGS: 00000246 ORIG_RAX: 00000000000000e8 RAX: ffffffffffffffda RBX: 0000000000000bb8 RCX: 00007f32ea1ef943 RDX: 0000000000000008 RSI: 00007ffff15b0e00 RDI: 000000000000000a RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000bb8 R11: 0000000000000246 R12: 0000000000000003 R13: 0000000000000000 R14: 0000000001137980 R15: 0000000001136250