Message-ID: <CACT4Y+a_8mnZQ_VQvHuYBXrUk9G0PhyZRTSx8JtX+f8-hG-Kvw@mail.gmail.com>
Date:   Tue, 12 Dec 2017 17:51:45 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot 
        <bot+d32d1ce36ec857115b638b70c3e23772f10d7462@...kaller.appspotmail.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        syzkaller-bugs@...glegroups.com, Jens Axboe <axboe@...nel.dk>,
        Ming Lei <tom.leiming@...il.com>,
        Omar Sandoval <osandov@...com>, Hannes Reinecke <hare@...e.de>,
        shli@...com
Subject: Re: INFO: task hung in pagecache_get_page

On Tue, Dec 5, 2017 at 9:11 PM, syzbot
<bot+d32d1ce36ec857115b638b70c3e23772f10d7462@...kaller.appspotmail.com>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> 2391f0b4808e3d5af348324d69f5f45c56a26836
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
>
> Unfortunately, I don't have any reproducer for this bug yet.
>
>
> unregister_netdevice: waiting for   to become free. Usage count = 2
> INFO: task syz-executor0:23858 blocked for more than 120 seconds.
>       Not tainted 4.15.0-rc2+ #207
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> syz-executor0   D24384 23858   3346 0x00000004
> Call Trace:
>  context_switch kernel/sched/core.c:2799 [inline]
>  __schedule+0x8eb/0x2060 kernel/sched/core.c:3375
>  schedule+0xf5/0x430 kernel/sched/core.c:3434
>  io_schedule+0x1c/0x70 kernel/sched/core.c:5042
>  wait_on_page_bit_common mm/filemap.c:1100 [inline]
>  __lock_page+0x585/0x740 mm/filemap.c:1273
>  lock_page include/linux/pagemap.h:483 [inline]
>  pagecache_get_page+0x672/0xba0 mm/filemap.c:1554
>  find_lock_page include/linux/pagemap.h:297 [inline]
>  truncate_inode_pages_range+0xc05/0x1f90 mm/truncate.c:400
>  blkdev_fallocate+0x1ff/0x3b0 fs/block_dev.c:1991
>  vfs_fallocate+0x342/0x700 fs/open.c:319
>  SYSC_fallocate fs/open.c:342 [inline]
>  SyS_fallocate+0x53/0x90 fs/open.c:336
>  entry_SYSCALL_64_fastpath+0x1f/0x96
> RIP: 0033:0x4529d9
> RSP: 002b:00007f2587578c58 EFLAGS: 00000212 ORIG_RAX: 000000000000011d
> RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 00000000004529d9
> RDX: 0000000000000000 RSI: 0000000000000011 RDI: 0000000000000019
> RBP: 0000000000000408 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000044400004 R11: 0000000000000212 R12: 00000000006f3160
> R13: 00000000ffffffff R14: 00007f25875796d4 R15: 0000000000000000
>
> Showing all locks held in the system:
> 2 locks held by khungtaskd/674:
>  #0:  (rcu_read_lock){....}, at: [<00000000e30adf30>]
> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
>  #0:  (rcu_read_lock){....}, at: [<00000000e30adf30>] watchdog+0x1c5/0xd60
> kernel/hung_task.c:249
>  #1:  (tasklist_lock){.?.?}, at: [<000000009ab1356f>]
> debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
> 2 locks held by getty/3053:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000002fbbac43>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a3f10257>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3054:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000002fbbac43>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a3f10257>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> unregister_netdevice: waiting for   to become free. Usage count = 2
> 2 locks held by getty/3055:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000002fbbac43>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a3f10257>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3056:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000002fbbac43>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a3f10257>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3057:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000002fbbac43>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a3f10257>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3058:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000002fbbac43>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a3f10257>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 3 locks held by kworker/u4:6/3916:
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<000000008938d852>]
> __write_once_size include/linux/compiler.h:212 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<000000008938d852>]
> atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<000000008938d852>]
> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<000000008938d852>]
> set_work_data kernel/workqueue.c:618 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<000000008938d852>]
> set_work_pool_and_clear_pending kernel/workqueue.c:645 [inline]
>  #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<000000008938d852>]
> process_one_work+0xad4/0x1be0 kernel/workqueue.c:2083
>  #1:  (net_cleanup_work){+.+.}, at: [<00000000f13a63c1>]
> process_one_work+0xb2f/0x1be0 kernel/workqueue.c:2087
>  #2:  (net_mutex){+.+.}, at: [<00000000a76af5a4>] cleanup_net+0x247/0xb60
> net/core/net_namespace.c:450
> 2 locks held by getty/23956:
>  #0:  (&tty->ldisc_sem){++++}, at: [<000000002fbbac43>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a3f10257>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
>
> =============================================
>
> NMI backtrace for cpu 1
> CPU: 1 PID: 674 Comm: khungtaskd Not tainted 4.15.0-rc2+ #207
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>  nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
>  nmi_trigger_cpumask_backtrace+0x122/0x180 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:138 [inline]
>  check_hung_task kernel/hung_task.c:132 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
>  watchdog+0x90c/0xd60 kernel/hung_task.c:249
>  kthread+0x37a/0x440 kernel/kthread.c:238
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441
> Sending NMI from CPU 1 to CPUs 0:
> NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10
> arch/x86/include/asm/irqflags.h:54

+loop maintainers

#syz dup: INFO: task hung in lo_ioctl


> ---
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> See https://goo.gl/tpsmEJ for details.
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