INFO: task syz-executor1:22547 blocked for more than 140 seconds. Not tainted 4.9.117-g8b21e85 #19 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor1 D28136 22547 3872 0x00000004 ffff8801d088c800 0000000000000000 ffff8801bbc12f40 ffff8801d9a6b000 ffff8801db321c18 ffff8801cb697ae8 ffffffff839ebd0d ffffffff81235687 0000000000000000 ffff8801d088d0c0 0000000600000007 ffff8801db3224e8 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3553 [] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline] [] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555 [] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105 [] __down_write arch/x86/include/asm/rwsem.h:125 [inline] [] down_write+0x5c/0xa0 kernel/locking/rwsem.c:54 [] inode_lock include/linux/fs.h:766 [inline] [] chmod_common+0x171/0x450 fs/open.c:543 [] SYSC_fchmod fs/open.c:568 [inline] [] SyS_fchmod+0xb3/0x110 fs/open.c:561 [] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282 [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Showing all locks held in the system: 2 locks held by khungtaskd/519: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x11c/0xa20 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336 2 locks held by getty/3753: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+...}, at: [] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142 2 locks held by syz-executor1/22494: #0: (sb_writers#20){.+.+.+}, at: [] sb_start_write include/linux/fs.h:1573 [inline] #0: (sb_writers#20){.+.+.+}, at: [] mnt_want_write+0x3f/0xb0 fs/namespace.c:391 #1: (&sb->s_type->i_mutex_key#27){++++++}, at: [] inode_lock include/linux/fs.h:766 [inline] #1: (&sb->s_type->i_mutex_key#27){++++++}, at: [] chmod_common+0x171/0x450 fs/open.c:543 2 locks held by syz-executor1/22547: #0: (sb_writers#20){.+.+.+}, at: [] sb_start_write include/linux/fs.h:1573 [inline] #0: (sb_writers#20){.+.+.+}, at: [] mnt_want_write+0x3f/0xb0 fs/namespace.c:391 #1: (&sb->s_type->i_mutex_key#27){++++++}, at: [] inode_lock include/linux/fs.h:766 [inline] #1: (&sb->s_type->i_mutex_key#27){++++++}, at: [] chmod_common+0x171/0x450 fs/open.c:543 1 lock held by syz-executor1/22549: #0: (sb_writers#20){.+.+.+}, at: [] sb_start_write include/linux/fs.h:1573 [inline] #0: (sb_writers#20){.+.+.+}, at: [] mnt_want_write+0x3f/0xb0 fs/namespace.c:391 2 locks held by syz-executor1/22550: #0: (sb_writers#20){.+.+.+}, at: [] sb_start_write include/linux/fs.h:1573 [inline] #0: (sb_writers#20){.+.+.+}, at: [] mnt_want_write_file+0x68/0x110 fs/namespace.c:449 #1: (&sb->s_type->i_mutex_key#27){++++++}, at: [] inode_lock include/linux/fs.h:766 [inline] #1: (&sb->s_type->i_mutex_key#27){++++++}, at: [] vfs_removexattr+0x79/0x1a0 fs/xattr.c:392 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.117-g8b21e85 #19 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d84dfd08 ffffffff81eb4be9 0000000000000000 0000000000000001 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d84dfd40 ffffffff81ebfee7 0000000000000001 0000000000000000 0000000000000003 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60 [] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x6b4/0xa20 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff839fb816