Hello, syzkaller hit the following crash on 82bcf1def3b5f1251177ad47c44f7e17af039b4b git://git.cmpxchg.org/linux-mmots.git/master compiler: gcc (GCC) 7.1.1 20170620 .config is attached Raw console output is attached. C reproducer is attached syzkaller reproducer is attached. See https://goo.gl/kgGztJ for information about syzkaller reproducers INFO: task syzkaller265413:3189 blocked for more than 120 seconds. Not tainted 4.15.0-rc2-mm1+ #39 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syzkaller265413 D24320 3189 3150 0x80000000 Call Trace: context_switch kernel/sched/core.c:2800 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3376 schedule+0xf5/0x430 kernel/sched/core.c:3435 schedule_timeout+0x43a/0x560 kernel/time/timer.c:1776 do_wait_for_common kernel/sched/completion.c:91 [inline] __wait_for_common kernel/sched/completion.c:112 [inline] wait_for_common kernel/sched/completion.c:123 [inline] wait_for_completion+0x44b/0x7b0 kernel/sched/completion.c:144 exit_aio+0x47f/0x530 fs/aio.c:903 __mmput kernel/fork.c:968 [inline] mmput+0x1b1/0x6c0 kernel/fork.c:992 exit_mm kernel/exit.c:544 [inline] do_exit+0x90a/0x1ae0 kernel/exit.c:856 do_group_exit+0x149/0x400 kernel/exit.c:972 SYSC_exit_group kernel/exit.c:983 [inline] SyS_exit_group+0x1d/0x20 kernel/exit.c:981 entry_SYSCALL_64_fastpath+0x1f/0x96 RIP: 0033:0x440a99 RSP: 002b:00007ffc5abebf68 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000440a99 RDX: 0000000000440a99 RSI: 0000000000000058 RDI: 0000000000000000 RBP: 000000000001cbc8 R08: 000000005abec108 R09: 0000000000401fd0 R10: 000000005abec108 R11: 0000000000000202 R12: 0000000000000000 R13: 0000000000401fd0 R14: 0000000000000000 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/673: #0: (rcu_read_lock){....}, at: [<00000000a9ed5249>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000a9ed5249>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<0000000036eecee2>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554 2 locks held by getty/3117: #0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3118: #0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3119: #0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3120: #0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3121: #0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3122: #0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3123: #0: (&tty->ldisc_sem){++++}, at: [<000000008d3f9495>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fafb010f>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 673 Comm: khungtaskd Not tainted 4.15.0-rc2-mm1+ #39 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x122/0x180 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+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x37a/0x440 kernel/kthread.c:238 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54 --- This bug is generated by a dumb bot. 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