INFO: task syz-executor2:5983 blocked for more than 140 seconds. Not tainted 4.20.0-rc6+ #150 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor2 D14328 5983 1 0x80000004 Call Trace: context_switch kernel/sched/core.c:2831 [inline] __schedule+0x8cf/0x21d0 kernel/sched/core.c:3472 schedule+0xfe/0x460 kernel/sched/core.c:3516 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3574 __mutex_lock_common kernel/locking/mutex.c:1002 [inline] __mutex_lock+0xaff/0x16f0 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 acct_get kernel/acct.c:161 [inline] slow_acct_process kernel/acct.c:577 [inline] acct_process+0x48b/0x875 kernel/acct.c:605 do_exit+0x1b89/0x26d0 kernel/exit.c:857 do_group_exit+0x177/0x440 kernel/exit.c:970 get_signal+0x8b0/0x1980 kernel/signal.c:2517 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816 exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x41135a Code: 65 0f 57 c0 f2 48 0f 2a c3 f2 0f 59 c1 f2 0f 10 0d 1b 05 57 00 f2 0f 59 c8 f2 0f 58 d1 f2 0f 10 05 23 06 57 00 f2 0f 5c d0 0f <57> c0 66 0f 2e d0 76 2f 0f 57 c0 0f 57 c9 f2 48 0f 2a c8 f2 0f 10 RSP: 002b:00007ffed5527df8 EFLAGS: 00000246 ORIG_RAX: 000000000000003d RAX: fffffffffffffe00 RBX: 00000000022fc9b3 RCX: 000000000041135a RDX: 0000000040000000 RSI: 00007ffed5527e30 RDI: ffffffffffffffff RBP: 0000000000000ad0 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000022fc940 R13: 0000000000000004 R14: 0000000000000382 R15: 0000000000000002 Showing all locks held in the system: 1 lock held by khungtaskd/1019: #0: 000000002828c9e2 (rcu_read_lock){....}, at: debug_show_all_locks+0xd0/0x424 kernel/locking/lockdep.c:4379 2 locks held by getty/5920: #0: 00000000bc8f6068 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 00000000a5677486 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/5921: #0: 00000000bc37aadb (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 000000000d9e4de6 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/5922: #0: 0000000022b0f217 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 00000000b883d3f5 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/5923: #0: 00000000a63bf6ec (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 0000000033e72870 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/5924: #0: 000000001b9d6a86 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 000000009719cecf (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/5925: #0: 00000000ad71f8a7 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 000000004f74d835 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/5926: #0: 000000005a16cea6 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 000000008120d351 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 1 lock held by syz-executor2/5983: #0: 00000000c166f0ae (&acct->lock#2){+.+.}, at: acct_get kernel/acct.c:161 [inline] #0: 00000000c166f0ae (&acct->lock#2){+.+.}, at: slow_acct_process kernel/acct.c:577 [inline] #0: 00000000c166f0ae (&acct->lock#2){+.+.}, at: acct_process+0x48b/0x875 kernel/acct.c:605 1 lock held by syz-executor5/21249: #0: 000000007d924c65 (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds+0x53/0x120 fs/exec.c:1404 1 lock held by syz-executor0/23473: #0: 000000001e1e8715 (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds+0x53/0x120 fs/exec.c:1404 1 lock held by syz-executor0/23492: #0: 0000000011bcd1b8 (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds+0x53/0x120 fs/exec.c:1404 3 locks held by syz-executor2/26508: #0: 00000000c166f0ae (&acct->lock#2){+.+.}, at: acct_get kernel/acct.c:161 [inline] #0: 00000000c166f0ae (&acct->lock#2){+.+.}, at: slow_acct_process kernel/acct.c:577 [inline] #0: 00000000c166f0ae (&acct->lock#2){+.+.}, at: acct_process+0x48b/0x875 kernel/acct.c:605 #1: 000000005c723bfb (sb_writers#3){.+.+}, at: file_start_write_trylock include/linux/fs.h:2817 [inline] #1: 000000005c723bfb (sb_writers#3){.+.+}, at: do_acct_process+0x1338/0x1660 kernel/acct.c:517 #2: 00000000b5d83ef4 (&sb->s_type->i_mutex_key#9){++++}, at: inode_trylock include/linux/fs.h:777 [inline] #2: 00000000b5d83ef4 (&sb->s_type->i_mutex_key#9){++++}, at: ext4_file_write_iter+0x2a1/0x1420 fs/ext4/file.c:232 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1019 Comm: khungtaskd Not tainted 4.20.0-rc6+ #150 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+0x244/0x39d lib/dump_stack.c:113 nmi_cpu_backtrace.cold.2+0x5c/0xa1 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1e8/0x22a 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:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline] watchdog+0xb51/0x1060 kernel/hung_task.c:289 kthread+0x35a/0x440 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:57