syzbot

INFO: task syz-executor.5:22514 blocked for more than 140 seconds.
      Not tainted 4.9.155+ #27
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D29480 22514  21827 0x00000004
 ffff8801a5a90000 0000000000000000 ffff8801db721000 ffff8801da6b2f80
 ffff8801db721018 ffff8801982f77b0 ffffffff82806806 dffffc0000000000
 ffff8801982f7788 ffffffff81207081 00ffffff8281194f ffff8801db7218f0
Call Trace:
 [<ffffffff82807d92>] schedule+0x92/0x1c0 kernel/sched/core.c:3553
 [<ffffffff82811bb3>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff82811bb3>] rwsem_down_write_failed+0x3a3/0x750 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81b79027>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff8281095c>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff8281095c>] down_write+0x5c/0xa0 kernel/locking/rwsem.c:54
 [<ffffffff81505280>] inode_lock include/linux/fs.h:768 [inline]
 [<ffffffff81505280>] do_truncate2+0x130/0x210 fs/open.c:61
 [<ffffffff8153f28e>] handle_truncate fs/namei.c:3031 [inline]
 [<ffffffff8153f28e>] do_last fs/namei.c:3466 [inline]
 [<ffffffff8153f28e>] path_openat+0x12ae/0x2f60 fs/namei.c:3581
 [<ffffffff81543d21>] do_filp_open+0x1a1/0x280 fs/namei.c:3615
 [<ffffffff815080c0>] do_sys_open+0x2f0/0x610 fs/open.c:1072
 [<ffffffff81508487>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff81508487>] SyS_open fs/open.c:1085 [inline]
 [<ffffffff81508487>] SYSC_creat fs/open.c:1110 [inline]
 [<ffffffff81508487>] SyS_creat+0x27/0x30 fs/open.c:1108
 [<ffffffff810056bd>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<ffffffff82816a93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131bbab>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131bbab>] watchdog+0x11b/0xa40 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff813fea8f>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336
2 locks held by getty/2022:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82814b83>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81d3982e>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
2 locks held by syz-executor.4/18581:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82814b83>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81d3982e>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
2 locks held by syz-executor.5/22514:
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff81577c8f>] sb_start_write include/linux/fs.h:1575 [inline]
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff81577c8f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [<ffffffff81505280>] inode_lock include/linux/fs.h:768 [inline]
 #1:  (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [<ffffffff81505280>] do_truncate2+0x130/0x210 fs/open.c:61

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.155+ #27
 ffff8801d9907cd0 ffffffff81b47871 0000000000000001 0000000000000000
 0000000000000001 ffffffff81097301 00000000003fff5d ffff8801d9907d08
 ffffffff81b52afc 0000000000000001 0000000000000000 0000000000000001
Call Trace:
 [<ffffffff81b47871>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b47871>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff81b52afc>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81b52a84>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<ffffffff81097494>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8131c087>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8131c087>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8131c087>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8131c087>] watchdog+0x5f7/0xa40 kernel/hung_task.c:239
 [<ffffffff81142028>] kthread+0x278/0x310 kernel/kthread.c:211
 [<ffffffff82816c5c>] 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
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.155+ #27
task: ffffffff8302d180 task.stack: ffffffff83000000
RIP: 0010:[<ffffffff8124376a>] 
c [<ffffffff8124376a>] debug_lockdep_rcu_enabled.part.0+0x2a/0x60 kernel/rcu/update.c:265
RSP: 0018:ffff8801db607c98  EFLAGS: 00000803
RAX: dffffc0000000000 RBX: ffffffff8302d180 RCX: 1ffffffff063ed60
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8302da2c
RBP: ffff8801db607ca0 R08: 0000000000000000 R09: ffff8801db621100
R10: ffff88021fffd010 R11: 0000012d5b9c9e92 R12: 0000000000000000
R13: ffff8801db6210a0 R14: ffff8801db621170 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c4268b1000 CR3: 00000001d066d000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000955
c ffff8801db607cb0
c ffffffff81243811
c ffff8801db607db0
c
 ffffffff811914cf
c ffffffff81babb7c
c ffffffff81babb7c
c ffffffff831f6b00
c
 0000000000000001
c ffff8801db61c5d0
c ffff8801db61cb00
c dffffc0000000000
c
Call Trace:
 <IRQ> 
d [<ffffffff81243811>] debug_lockdep_rcu_enabled+0x71/0xa0 kernel/rcu/update.c:264
 [<ffffffff811914cf>] trace_sched_contrib_scale_f include/trace/events/sched.h:590 [inline]
 [<ffffffff811914cf>] __update_load_avg kernel/sched/fair.c:2873 [inline]
 [<ffffffff811914cf>] update_cfs_rq_load_avg kernel/sched/fair.c:3291 [inline]
 [<ffffffff811914cf>] update_blocked_averages+0x1e7f/0x4f70 kernel/sched/fair.c:8218
 [<ffffffff811d1264>] rebalance_domains+0xf4/0x960 kernel/sched/fair.c:10092
 [<ffffffff811d1dc0>] run_rebalance_domains+0x2f0/0x500 kernel/sched/fair.c:10349
 [<ffffffff8281be7d>] __do_softirq+0x22d/0x964 kernel/softirq.c:288
 [<ffffffff810eecd9>] invoke_softirq kernel/softirq.c:368 [inline]
 [<ffffffff810eecd9>] irq_exit+0x119/0x160 kernel/softirq.c:409
 [<ffffffff8281994e>] smp_reschedule_interrupt+0x6e/0x90 arch/x86/kernel/smp.c:270
 [<ffffffff828187ad>] reschedule_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:671
 <EOI> 
d [<ffffffff82815692>] ? native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:56
 [<ffffffff81068160>] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:428
 [<ffffffff82815ae6>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff811f1233>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff811f1233>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff811f1233>] cpu_startup_entry+0x283/0x3a0 kernel/sched/idle.c:303
 [<ffffffff82804124>] rest_init+0x18b/0x194 init/main.c:409
 [<ffffffff83420948>] start_kernel+0x619/0x64d init/main.c:664
 [<ffffffff8341f29a>] x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:196
 [<ffffffff8341f3d3>] x86_64_start_kernel+0x137/0x15a arch/x86/kernel/head64.c:177
Code: 
c90 
c48 
cb8 
c00 
c00 
c00 
c00 
c00 
cfc 
cff 
cdf 
c55 
c48 
c89 
ce5 
c53 
c65 
c48 
c8b 
c1c 
c25 
c00 
c7e 
c01 
c00 
c48 
c8d 
cbb 
cac 
c08 
c00 
c00 
c48 
c89 
cfa 
c48 
cc1 
cea 
c03 
c0f 
cb6 
c14 
c02 
c<48> 
c89 
cf8 
c83 
ce0 
c07 
c83 
cc0 
c03 
c38 
cd0 
c7c 
c04 
c84 
cd2 
c75 
c10 
c8b 
c93 
cac 
c08 
c