INFO: task syz-executor0:8260 blocked for more than 120 seconds. Not tainted 4.17.0+ #86 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor0 D23912 8260 4589 0x00000004 Call Trace: context_switch kernel/sched/core.c:2856 [inline] __schedule+0x801/0x1e30 kernel/sched/core.c:3498 schedule+0xef/0x430 kernel/sched/core.c:3542 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3600 __mutex_lock_common kernel/locking/mutex.c:834 [inline] __mutex_lock+0xe38/0x17f0 kernel/locking/mutex.c:894 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:909 __fdget_pos+0x1a9/0x1e0 fs/file.c:766 fdget_pos include/linux/file.h:67 [inline] ksys_read+0x77/0x250 fs/read_write.c:573 __do_sys_read fs/read_write.c:588 [inline] __se_sys_read fs/read_write.c:586 [inline] __x64_sys_read+0x73/0xb0 fs/read_write.c:586 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x455a09 Code: Bad RIP value. RSP: 002b:00007f2543594c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007f25435956d4 RCX: 0000000000455a09 RDX: 0000000000000058 RSI: 00000000200004c0 RDI: 0000000000000013 RBP: 000000000072bf50 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000566 R14: 00000000006fd230 R15: 0000000000000001 Showing all locks held in the system: 3 locks held by kworker/u4:5/273: 2 locks held by khungtaskd/896: #0: 00000000e4a73d1a (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: 00000000e4a73d1a (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249 #1: 00000000e4a73d1a (rcu_read_lock){....}, at: debug_show_all_locks+0xc8/0x40c kernel/locking/lockdep.c:4461 1 lock held by rsyslogd/4419: 2 locks held by getty/4511: #0: 00000000315034a8 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000251427a6 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4512: #0: 0000000005d6d686 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000ed4811b1 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4513: #0: 00000000239f5cba (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000052f7c017 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4514: #0: 000000002ef7aec7 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000d3ad561e (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4515: #0: 00000000b7f12351 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000007803bbe7 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4516: #0: 000000008525ce04 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000004b90da57 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4517: #0: 000000004d5bc967 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000acdedb22 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 4 locks held by syz-executor0/8188: 1 lock held by syz-executor0/8260: #0: 00000000c929fd25 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1a9/0x1e0 fs/file.c:766 1 lock held by syz-executor0/8262: #0: 00000000c929fd25 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1a9/0x1e0 fs/file.c:766 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 896 Comm: khungtaskd Not tainted 4.17.0+ #86 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+0x1b9/0x294 lib/dump_stack.c:113 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0xc10/0xf60 kernel/hung_task.c:249 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 273 Comm: kworker/u4:5 Not tainted 4.17.0+ #86 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: writeback wb_workfn (flush-7:0) RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline] RIP: 0010:check_kcov_mode kernel/kcov.c:69 [inline] RIP: 0010:__sanitizer_cov_trace_pc+0x26/0x50 kernel/kcov.c:101 Code: 5d c3 66 90 55 65 48 8b 04 25 40 ee 01 00 65 8b 15 ff 94 88 7e 48 89 e5 81 e2 00 01 1f 00 48 8b 75 08 75 2b 8b 90 78 12 00 00 <83> fa 02 75 20 48 8b 88 80 12 00 00 8b 80 7c 12 00 00 48 8b 11 48 RSP: 0018:ffff8801d8d96340 EFLAGS: 00000246 RAX: ffff8801d8d76700 RBX: ffff8801b447a2d8 RCX: ffffffff81cf9b17 RDX: 0000000000000000 RSI: ffffffff81d0e88d RDI: ffff8801b447a2d8 RBP: ffff8801d8d96340 R08: ffff8801d8d76700 R09: ffffed003b5c46d6 R10: 0000000000000003 R11: 0000000000000003 R12: 0000000000000000 R13: 0000000000000040 R14: 0000000000000001 R15: ffffea0006db9760 FS: 0000000000000000(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffff600400 CR3: 00000001b36fd000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: I_BDEV+0xd/0x20 fs/block_dev.c:53 init_page_buffers+0x1cb/0x510 fs/buffer.c:891 grow_dev_page fs/buffer.c:947 [inline] grow_buffers fs/buffer.c:1009 [inline] __getblk_slow fs/buffer.c:1036 [inline] __getblk_gfp+0x8e9/0xaf0 fs/buffer.c:1313 __bread_gfp+0x2d/0x310 fs/buffer.c:1347 sb_bread include/linux/buffer_head.h:307 [inline] __fat_write_inode+0x33f/0xb40 fs/fat/inode.c:845 fat_write_inode+0x97/0x180 fs/fat/inode.c:894 write_inode fs/fs-writeback.c:1183 [inline] __writeback_single_inode+0xf18/0x15c0 fs/fs-writeback.c:1382 writeback_sb_inodes+0x6f0/0x11a0 fs/fs-writeback.c:1587 __writeback_inodes_wb+0x1b0/0x320 fs/fs-writeback.c:1656 wb_writeback+0x9e4/0xf50 fs/fs-writeback.c:1765 wb_check_background_flush fs/fs-writeback.c:1833 [inline] wb_do_writeback fs/fs-writeback.c:1921 [inline] wb_workfn+0xd08/0x1740 fs/fs-writeback.c:1949 process_one_work+0xc64/0x1b70 kernel/workqueue.c:2153 worker_thread+0x181/0x13a0 kernel/workqueue.c:2296 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.296 msecs