INFO: task syz-executor4:6335 blocked for more than 140 seconds. Not tainted 4.20.0 #166 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor4 D15032 6335 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2831 [inline] __schedule+0x86c/0x1ed0 kernel/sched/core.c:3472 schedule+0xfe/0x460 kernel/sched/core.c:3516 __rwsem_down_write_failed_common+0xbbc/0x15e0 kernel/locking/rwsem-xadd.c:577 rwsem_down_write_failed+0xe/0x10 kernel/locking/rwsem-xadd.c:606 call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117 __down_write arch/x86/include/asm/rwsem.h:142 [inline] down_write+0xa5/0x130 kernel/locking/rwsem.c:72 inode_lock include/linux/fs.h:757 [inline] vfs_unlink+0xd1/0x510 fs/namei.c:3990 do_unlinkat+0x6cc/0xa30 fs/namei.c:4062 __do_sys_unlink fs/namei.c:4109 [inline] __se_sys_unlink fs/namei.c:4107 [inline] __x64_sys_unlink+0x42/0x50 fs/namei.c:4107 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4573b7 Code: 00 66 90 b8 58 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 9d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 57 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 7d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffc2ab84378 EFLAGS: 00000246 ORIG_RAX: 0000000000000057 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004573b7 RDX: 00007ffc2ab84390 RSI: 00007ffc2ab84390 RDI: 00007ffc2ab84420 RBP: 00000000000029cc R08: 0000000000000000 R09: 000000000000000c R10: 0000000000000005 R11: 0000000000000246 R12: 00007ffc2ab854b0 R13: 000000000176d940 R14: 0000000000000000 R15: 0000000000000004 Showing all locks held in the system: 1 lock held by khungtaskd/1020: #0: 0000000003c384d6 (rcu_read_lock){....}, at: debug_show_all_locks+0xd0/0x424 kernel/locking/lockdep.c:4379 1 lock held by rsyslogd/6030: #0: 0000000033947381 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1bb/0x200 fs/file.c:766 2 locks held by getty/6152: #0: 00000000e6380163 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 0000000011a5531b (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/6153: #0: 00000000c86ca5f8 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 00000000abcc5d33 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/6154: #0: 00000000a4f1e49b (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 000000002de8787b (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/6155: #0: 0000000058cc35b0 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 00000000a6ab6b19 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/6156: #0: 00000000b5e3f141 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 000000001c7606d2 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/6157: #0: 00000000fa4e670c (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 000000004558f0bc (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 2 locks held by getty/6158: #0: 00000000b1b01ca7 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 00000000451e9760 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154 3 locks held by syz-executor4/6335: #0: 00000000aaa651ca (sb_writers#4){.+.+}, at: sb_start_write include/linux/fs.h:1597 [inline] #0: 00000000aaa651ca (sb_writers#4){.+.+}, at: mnt_want_write+0x3f/0xc0 fs/namespace.c:360 #1: 000000009242dac7 (&type->i_mutex_dir_key#3/1){+.+.}, at: inode_lock_nested include/linux/fs.h:792 [inline] #1: 000000009242dac7 (&type->i_mutex_dir_key#3/1){+.+.}, at: do_unlinkat+0x3d8/0xa30 fs/namei.c:4048 #2: 000000008e4e4bf5 (&sb->s_type->i_mutex_key#9){++++}, at: inode_lock include/linux/fs.h:757 [inline] #2: 000000008e4e4bf5 (&sb->s_type->i_mutex_key#9){++++}, at: vfs_unlink+0xd1/0x510 fs/namei.c:3990 2 locks held by syz-executor4/29410: #0: 00000000aaa651ca (sb_writers#4){.+.+}, at: file_start_write include/linux/fs.h:2810 [inline] #0: 00000000aaa651ca (sb_writers#4){.+.+}, at: vfs_write+0x42a/0x560 fs/read_write.c:548 #1: 000000008e4e4bf5 (&sb->s_type->i_mutex_key#9){++++}, at: inode_trylock include/linux/fs.h:777 [inline] #1: 000000008e4e4bf5 (&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: 1020 Comm: khungtaskd Not tainted 4.20.0 #166 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+0x1d3/0x2c6 lib/dump_stack.c:113 nmi_cpu_backtrace.cold.4+0x63/0xa2 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1c2/0x22c 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