INFO: task syz-executor.4:20254 blocked for more than 140 seconds.
      Not tainted 4.9.194+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D28736 20254   2092 0x00000004
 0000000000000087 ffff880191ddaf80 ffff8801d00c2680 ffff8801db721000
 ffff8801d10f8000 ffff8801db721018 ffff88017a9e7c90 ffffffff8281af8e
 ffffffff8282635c ffff8801ca512aa8 00ff88017a9e7be0 ffff8801db7218f0
Call Trace:
 [<000000001ccdfc0f>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<000000003ebef871>] rwsem_down_read_failed+0x258/0x3e0 kernel/locking/rwsem-xadd.c:283
 [<00000000dbff86e2>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<000000007cfe8db8>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<000000007cfe8db8>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<00000000fc53b3ed>] __do_page_fault+0x7bd/0xa60 arch/x86/mm/fault.c:1337
 [<000000006d264c70>] do_page_fault+0x28/0x30 arch/x86/mm/fault.c:1464
 [<0000000004ab8a8f>] page_fault+0x25/0x30 arch/x86/entry/entry_64.S:956

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<00000000ccca6621>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<00000000ccca6621>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<0000000018653fed>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336
2 locks held by getty/2018:
 #0:  (&tty->ldisc_sem){++++++}, at: [<00000000e921ae24>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<00000000f924bcf9>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.4/20254:
 #0:  (&mm->mmap_sem){++++++}, at: [<00000000fc53b3ed>] __do_page_fault+0x7bd/0xa60 arch/x86/mm/fault.c:1337
1 lock held by syz-executor.4/20255:
 #0:  (&mm->mmap_sem){++++++}, at: [<00000000256a49fc>] exit_mm kernel/exit.c:480 [inline]
 #0:  (&mm->mmap_sem){++++++}, at: [<00000000256a49fc>] do_exit+0x3bb/0x2aa0 kernel/exit.c:829

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

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.194+ #0
 ffff8801d98d7cc8 ffffffff81b67001 0000000000000000 0000000000000000
 0000000000000000 ffffffff81099d01 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b7229c 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<000000008a636b4b>] __dump_stack lib/dump_stack.c:15 [inline]
 [<000000008a636b4b>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<000000003b5c420c>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<00000000c4cc29a1>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<000000005ffb2fbd>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<00000000be9556ff>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<00000000be9556ff>] check_hung_task kernel/hung_task.c:126 [inline]
 [<00000000be9556ff>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline]
 [<00000000be9556ff>] watchdog+0x670/0xaf0 kernel/hung_task.c:263
 [<00000000604cc517>] kthread+0x278/0x310 kernel/kthread.c:211
 [<000000000f7d40af>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 2091 Comm: kworker/u4:3 Not tainted 4.9.194+ #0
Workqueue: writeback wb_workfn
c (flush-8:0)
c
task: 00000000ecc5d165 task.stack: 00000000a367531e
RIP: 0010:[<ffffffff810ae34a>] 
c [<0000000039a32fcb>] unwind_next_frame.part.0+0x1a/0x1a0 arch/x86/kernel/unwind_frame.c:60
RSP: 0018:ffff8801aa5decb0  EFLAGS: 00000202
RAX: dffffc0000000000 RBX: ffff8801aa5ded80 RCX: 0000000000000011
RDX: 0000000000000001 RSI: ffffffff8143dbfc RDI: ffff8801aa5decf8
RBP: ffff8801aa5decd0 R08: 0000000000000001 R09: ffff8801aa5ded20
R10: ffffed00354bbda6 R11: ffff8801aa5ded37 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8801aa5deca8 R15: ffff8801d9fa4140
FS:  0000000000000000(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa0f05ef000 CR3: 000000018e3a9000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000000
c 0000000000000000
c ffff8801d0ab4740
c ffff8801d9fa4140
c
 ffff8801aa5dece8
c ffffffff810ae502
c 0000000000000000
c ffff8801aa5ded60
c
 ffffffff81078b1a
c 0000000000000001
c ffff8801aa5d8000
c ffff8801aa5e0000
c
Call Trace:
 [<0000000074c1b0dc>] unwind_next_frame+0x32/0x50 arch/x86/kernel/unwind_frame.c:64
 [<000000006f4b1d7d>] __save_stack_trace+0x7a/0xf0 arch/x86/kernel/stacktrace.c:42
 [<000000000de3cfeb>] save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 [<00000000c49ee0c1>] save_stack mm/kasan/kasan.c:512 [inline]
 [<00000000c49ee0c1>] set_track mm/kasan/kasan.c:524 [inline]
 [<00000000c49ee0c1>] kasan_kmalloc.part.0+0x62/0xf0 mm/kasan/kasan.c:616
 [<00000000333cc13b>] kasan_kmalloc+0xb7/0xd0 mm/kasan/kasan.c:601
 [<00000000dc3187f1>] kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:554
 [<000000005b542306>] slab_post_alloc_hook mm/slab.h:417 [inline]
 [<000000005b542306>] slab_alloc_node mm/slub.c:2715 [inline]
 [<000000005b542306>] slab_alloc mm/slub.c:2723 [inline]
 [<000000005b542306>] kmem_cache_alloc+0xd5/0x2b0 mm/slub.c:2728
 [<000000009eab22f5>] mempool_alloc_slab+0x47/0x60 mm/mempool.c:449
 [<00000000c0c66156>] mempool_alloc+0x149/0x360 mm/mempool.c:329
 [<0000000004db0e59>] bio_alloc_bioset+0x3fb/0x7d0 block/bio.c:474
 [<00000000c25265e5>] bio_alloc include/linux/bio.h:393 [inline]
 [<00000000c25265e5>] submit_bh_wbc.isra.0+0xf3/0x590 fs/buffer.c:3083
 [<00000000281120c5>] __block_write_full_page+0x447/0x800 fs/buffer.c:1790
 [<00000000e489d554>] block_write_full_page+0x245/0x2b0 fs/buffer.c:2978
 [<0000000032f3da4c>] blkdev_writepage+0x25/0x30 fs/block_dev.c:326
 [<00000000e5a98491>] __writepage+0x63/0xc0 mm/page-writeback.c:2300
 [<00000000f0ba1eca>] write_cache_pages+0x577/0xe60 mm/page-writeback.c:2232
 [<000000002cc92209>] generic_writepages mm/page-writeback.c:2324 [inline]
 [<000000002cc92209>] generic_writepages+0xe6/0x160 mm/page-writeback.c:2313
 [<00000000acee8462>] blkdev_writepages+0x1e/0x30 fs/block_dev.c:1772
 [<00000000b1781fcd>] do_writepages+0xfc/0x1e0 mm/page-writeback.c:2338
 [<000000001b207cb6>] __writeback_single_inode+0xd9/0x1040 fs/fs-writeback.c:1364
 [<000000003e5fc60c>] writeback_sb_inodes+0x50f/0xea0 fs/fs-writeback.c:1628
 [<0000000074b42304>] __writeback_inodes_wb+0xc3/0x210 fs/fs-writeback.c:1697
 [<000000003165ec4c>] wb_writeback+0x637/0xbd0 fs/fs-writeback.c:1806
 [<000000009df834e1>] wb_check_background_flush fs/fs-writeback.c:1887 [inline]
 [<000000009df834e1>] wb_do_writeback fs/fs-writeback.c:1946 [inline]
 [<000000009df834e1>] wb_workfn+0x791/0xe70 fs/fs-writeback.c:1974
 [<0000000023b70119>] process_one_work+0x88b/0x1600 kernel/workqueue.c:2114
 [<00000000f2520882>] worker_thread+0x5df/0x11d0 kernel/workqueue.c:2251
 [<00000000604cc517>] kthread+0x278/0x310 kernel/kthread.c:211
 [<000000000f7d40af>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375
Code: 
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