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Date:   Sat, 24 Sep 2022 23:25:06 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     syzbot <syzbot+0e9dc403e57033a74b1d@syzkaller.appspotmail.com>
Cc:     akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] INFO: task hung in __filemap_get_folio
Message-ID: <Yy+DwlrnuBOKudoY@casper.infradead.org>
References: <0000000000002709ae05e5b6474c@google.com>
 <000000000000fc539605e95c95be@google.com>
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On Fri, Sep 23, 2022 at 11:45:46AM -0700, syzbot wrote:
> syzbot has found a reproducer for the following issue on:

No, it hasn't.  This is a different bug.  The other one is a bug in
NTFS.  This is ... something else?  Maybe nbd?  maybe fuse?

> HEAD commit:    bf682942cd26 Merge tag 'scsi-fixes' of git://git.kernel.or..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12096640880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7db7ad17eb14cb7
> dashboard link: https://syzkaller.appspot.com/bug?extid=0e9dc403e57033a74b1d
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116e80ff080000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11bfbbcf080000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+0e9dc403e57033a74b1d@syzkaller.appspotmail.com
> 
> INFO: task udevd:3638 blocked for more than 143 seconds.
>       Not tainted 6.0.0-rc6-syzkaller-00210-gbf682942cd26 #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:udevd           state:D stack:26248 pid: 3638 ppid:  2972 flags:0x00004006
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5182 [inline]
>  __schedule+0xadf/0x52b0 kernel/sched/core.c:6494
>  schedule+0xda/0x1b0 kernel/sched/core.c:6570
>  io_schedule+0xba/0x130 kernel/sched/core.c:8714
>  folio_wait_bit_common+0x3dd/0xa90 mm/filemap.c:1298
>  __folio_lock mm/filemap.c:1664 [inline]
>  folio_lock include/linux/pagemap.h:939 [inline]
>  folio_lock include/linux/pagemap.h:935 [inline]
>  __filemap_get_folio+0xc6d/0xed0 mm/filemap.c:1936
>  truncate_inode_pages_range+0x37c/0x1510 mm/truncate.c:378
>  kill_bdev block/bdev.c:75 [inline]
>  blkdev_flush_mapping+0x140/0x2f0 block/bdev.c:661
>  blkdev_put_whole+0xd1/0xf0 block/bdev.c:692
>  blkdev_put+0x226/0x770 block/bdev.c:952
>  blkdev_close+0x64/0x80 block/fops.c:499
>  __fput+0x277/0x9d0 fs/file_table.c:320
>  task_work_run+0xdd/0x1a0 kernel/task_work.c:177
>  exit_task_work include/linux/task_work.h:38 [inline]
>  do_exit+0xad5/0x29b0 kernel/exit.c:795
>  do_group_exit+0xd2/0x2f0 kernel/exit.c:925
>  get_signal+0x238c/0x2610 kernel/signal.c:2857
>  arch_do_signal_or_restart+0x82/0x2300 arch/x86/kernel/signal.c:869
>  exit_to_user_mode_loop kernel/entry/common.c:166 [inline]
>  exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:201
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
>  syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294
>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7fea11178697
> RSP: 002b:00007ffc3c7fb710 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
> RAX: 0000000000000008 RBX: 000055b3e78469c0 RCX: 00007fea11178697
> RDX: 00000000000a0800 RSI: 000055b3e7818920 RDI: 00000000ffffff9c
> RBP: 000055b3e7818920 R08: 0000000000000001 R09: 00007ffc3c816080
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000a0800
> R13: 000055b3e7819a80 R14: 00007ffc3c7fb7bc R15: 000055b3e780b2c0
>  </TASK>
> INFO: task syz-executor127:3645 blocked for more than 143 seconds.
>       Not tainted 6.0.0-rc6-syzkaller-00210-gbf682942cd26 #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor127 state:D stack:28376 pid: 3645 ppid:  3635 flags:0x00000004
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5182 [inline]
>  __schedule+0xadf/0x52b0 kernel/sched/core.c:6494
>  schedule+0xda/0x1b0 kernel/sched/core.c:6570
>  schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6629
>  __mutex_lock_common kernel/locking/mutex.c:679 [inline]
>  __mutex_lock+0xa44/0x1350 kernel/locking/mutex.c:747
>  blkdev_get_by_dev.part.0+0x9b/0xb90 block/bdev.c:812
>  blkdev_get_by_dev+0x6b/0x80 block/bdev.c:855
>  blkdev_open+0x13c/0x2c0 block/fops.c:485
>  do_dentry_open+0x4a4/0x13a0 fs/open.c:880
>  do_open fs/namei.c:3557 [inline]
>  path_openat+0x1c92/0x28f0 fs/namei.c:3691
>  do_filp_open+0x1b6/0x400 fs/namei.c:3718
>  do_sys_openat2+0x16d/0x4c0 fs/open.c:1313
>  do_sys_open fs/open.c:1329 [inline]
>  __do_sys_openat fs/open.c:1345 [inline]
>  __se_sys_openat fs/open.c:1340 [inline]
>  __x64_sys_openat+0x13f/0x1f0 fs/open.c:1340
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7ff1e173a4d7
> RSP: 002b:00007ffdf8c863c0 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ff1e173a4d7
> RDX: 0000000000000000 RSI: 00007ffdf8c86440 RDI: 00000000ffffff9c
> RBP: 00007ffdf8c86440 R08: 000000000000ffff R09: 00007ffdf8c862d0
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 431bde82d7b634db R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
> 
> Showing all locks held in the system:
> 1 lock held by rcu_tasks_kthre/12:
>  #0: ffffffff8bf85db0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x26/0xc70 kernel/rcu/tasks.h:507
> 1 lock held by rcu_tasks_trace/13:
>  #0: ffffffff8bf85ab0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x26/0xc70 kernel/rcu/tasks.h:507
> 1 lock held by khungtaskd/28:
>  #0: ffffffff8bf86900 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6492
> 1 lock held by klogd/2961:
>  #0: ffff8880b9a3a018 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2b/0x120 kernel/sched/core.c:544
> 2 locks held by getty/3287:
>  #0: ffff88801caa6098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:244
>  #1: ffffc90001c482f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xef0/0x13e0 drivers/tty/n_tty.c:2177
> 1 lock held by udevd/3638:
>  #0: ffff88801e6644c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xbc/0x770 block/bdev.c:910
> 1 lock held by syz-executor127/3645:
>  #0: ffff88801e6644c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev.part.0+0x9b/0xb90 block/bdev.c:812
> 
> =============================================
> 
> NMI backtrace for cpu 1
> CPU: 1 PID: 28 Comm: khungtaskd Not tainted 6.0.0-rc6-syzkaller-00210-gbf682942cd26 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  nmi_cpu_backtrace.cold+0x46/0x14f lib/nmi_backtrace.c:111
>  nmi_trigger_cpumask_backtrace+0x206/0x250 lib/nmi_backtrace.c:62
>  trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
>  watchdog+0xc18/0xf50 kernel/hung_task.c:369
>  kthread+0x2e4/0x3a0 kernel/kthread.c:376
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
>  </TASK>
> Sending NMI from CPU 1 to CPUs 0:
> NMI backtrace for cpu 0
> CPU: 0 PID: 41 Comm: kworker/u4:2 Not tainted 6.0.0-rc6-syzkaller-00210-gbf682942cd26 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
> Workqueue: events_unbound toggle_allocation_gate
> RIP: 0010:check_wait_context kernel/locking/lockdep.c:4741 [inline]
> RIP: 0010:__lock_acquire+0x574/0x56d0 kernel/locking/lockdep.c:5003
> Code: 00 00 45 89 fe 41 83 ee 01 0f 88 7c 13 00 00 49 b9 00 00 00 00 00 fc ff df 49 63 c6 48 8d 04 80 49 8d ac c5 99 0a 00 00 eb 12 <41> 83 ee 01 48 83 ed 28 41 83 fe ff 0f 84 15 0b 00 00 48 8d 5d df
> RSP: 0018:ffffc90000d2f738 EFLAGS: 00000046
> RAX: 0000000000000000 RBX: ffff8880174d0af8 RCX: 0000000000000001
> RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffffff908e8dd9
> RBP: ffff8880174d0b19 R08: 0000000000000000 R09: dffffc0000000000
> R10: fffffbfff211c32a R11: 0000000000000000 R12: ffff8880174d0bc0
> R13: ffff8880174d0080 R14: 0000000000000000 R15: 0000000000000005
> FS:  0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000056317ad90680 CR3: 000000000bc8e000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  lock_acquire kernel/locking/lockdep.c:5666 [inline]
>  lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
>  __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
>  _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
>  spin_lock include/linux/spinlock.h:349 [inline]
>  __get_locked_pte+0x154/0x270 mm/memory.c:1838
>  get_locked_pte include/linux/mm.h:2089 [inline]
>  __text_poke+0x1b3/0x8e0 arch/x86/kernel/alternative.c:1123
>  text_poke arch/x86/kernel/alternative.c:1208 [inline]
>  text_poke_bp_batch+0x147/0x6c0 arch/x86/kernel/alternative.c:1487
>  text_poke_flush arch/x86/kernel/alternative.c:1660 [inline]
>  text_poke_flush arch/x86/kernel/alternative.c:1657 [inline]
>  text_poke_finish+0x16/0x30 arch/x86/kernel/alternative.c:1667
>  arch_jump_label_transform_apply+0x13/0x20 arch/x86/kernel/jump_label.c:146
>  jump_label_update+0x32f/0x410 kernel/jump_label.c:801
>  static_key_disable_cpuslocked+0x152/0x1b0 kernel/jump_label.c:207
>  static_key_disable+0x16/0x20 kernel/jump_label.c:215
>  toggle_allocation_gate mm/kfence/core.c:825 [inline]
>  toggle_allocation_gate+0x183/0x390 mm/kfence/core.c:803
>  process_one_work+0x991/0x1610 kernel/workqueue.c:2289
>  worker_thread+0x665/0x1080 kernel/workqueue.c:2436
>  kthread+0x2e4/0x3a0 kernel/kthread.c:376
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
>  </TASK>
> INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.080 msecs
>