syzbot

INFO: task syz-executor6:18276 blocked for more than 120 seconds.
      Not tainted 4.9.107-gdb2c520 #49
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor6   D28672 18276   3883 0x00000004
 ffff88019701e000 ffff8801b7471500 ffff88018f94c540 ffff8801783d0000
 ffff8801db221c18 ffff880184a2f4a0 ffffffff839e8c1d 1ffff10030945e88
 ffffffff85542240 0000000041b58ab3 00ffffff843c2388 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea21f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839f6631>] schedule_timeout+0x861/0xf70 kernel/time/timer.c:1768
 [<ffffffff839e83fa>] io_schedule_timeout+0x1ba/0x390 kernel/sched/core.c:5180
 [<ffffffff839eb669>] io_schedule include/linux/sched.h:460 [inline]
 [<ffffffff839eb669>] bit_wait_io+0x19/0xa0 kernel/sched/wait.c:582
 [<ffffffff839eadb3>] __wait_on_bit+0x93/0x120 kernel/sched/wait.c:383
 [<ffffffff81433e80>] wait_on_page_bit+0x130/0x140 mm/filemap.c:802
 [<ffffffff8143fd67>] wait_on_page_locked include/linux/pagemap.h:517 [inline]
 [<ffffffff8143fd67>] __lock_page_or_retry+0x1f7/0x280 mm/filemap.c:975
 [<ffffffff81440393>] lock_page_or_retry include/linux/pagemap.h:481 [inline]
 [<ffffffff81440393>] filemap_fault+0x5a3/0x1130 mm/filemap.c:2140
 [<ffffffff814c147d>] __do_fault+0x22d/0x500 mm/memory.c:2827
 [<ffffffff814d0bae>] do_read_fault mm/memory.c:3174 [inline]
 [<ffffffff814d0bae>] do_fault mm/memory.c:3309 [inline]
 [<ffffffff814d0bae>] handle_pte_fault mm/memory.c:3510 [inline]
 [<ffffffff814d0bae>] __handle_mm_fault mm/memory.c:3597 [inline]
 [<ffffffff814d0bae>] handle_mm_fault+0x160e/0x28e0 mm/memory.c:3634
 [<ffffffff814bde66>] faultin_page mm/gup.c:386 [inline]
 [<ffffffff814bde66>] __get_user_pages+0x556/0x1180 mm/gup.c:588
 [<ffffffff814bf94a>] populate_vma_page_range+0x19a/0x230 mm/gup.c:1106
 [<ffffffff814bfbeb>] __mm_populate+0x20b/0x350 mm/gup.c:1156
 [<ffffffff81497ba5>] mm_populate include/linux/mm.h:2041 [inline]
 [<ffffffff81497ba5>] vm_mmap_pgoff+0x195/0x1b0 mm/util.c:333
 [<ffffffff814e0392>] SYSC_mmap_pgoff mm/mmap.c:1523 [inline]
 [<ffffffff814e0392>] SyS_mmap_pgoff+0x342/0x550 mm/mmap.c:1481
 [<ffffffff8105e0f6>] SYSC_mmap arch/x86/kernel/sys_x86_64.c:96 [inline]
 [<ffffffff8105e0f6>] SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:87
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9b13>] 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: [<ffffffff8136662c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136662c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425cb7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3678:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d7fac>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3774:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7cc2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211fc62>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.107-gdb2c520 #49
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8627d08 ffffffff81eb3da9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b96a0 ffff8801d8627d40
 ffffffff81ebf0a7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb3da9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3da9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf0a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf03a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b97a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366bc4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366bc4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366bc4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366bc4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9cdc>] 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 0xffffffff839f8726