Date:   Sat, 19 Jan 2019 20:03:43 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+cfa5d826b19395f1940e@...kaller.appspotmail.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.com>
Cc:     hirofumi@...l.parknet.co.jp, LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: INFO: task hung in fat_fallocate

On Sun, Apr 29, 2018 at 7:03 PM syzbot
<syzbot+cfa5d826b19395f1940e@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot hit the following crash on upstream commit
> bf8f5de17442bba5f811e7e724980730e079ee11 (Sat Apr 28 17:05:04 2018 +0000)
> MAINTAINERS: add myself as maintainer of AFFS
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=cfa5d826b19395f1940e
>
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=5087555854794752
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=7043958930931867332
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)

This mentions __getblk_gfp. Is it the same as "INFO: task hung in
generic_file_write_iter":
https://syzkaller.appspot.com/bug?id=b3c7e1440aa8ece16bf557dbac427fdff1dad9d6
and fixed with "blockdev: Fix livelocks on loop device"?


> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+cfa5d826b19395f1940e@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
>
> INFO: task syz-executor0:10251 blocked for more than 120 seconds.
>        Not tainted 4.17.0-rc2+ #22
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> syz-executor0   D25408 10251   7326 0x00000004
> Call Trace:
>   context_switch kernel/sched/core.c:2848 [inline]
>   __schedule+0x801/0x1e30 kernel/sched/core.c:3490
>   schedule+0xef/0x430 kernel/sched/core.c:3549
>   __rwsem_down_write_failed_common+0x919/0x15d0
> kernel/locking/rwsem-xadd.c:566
>   rwsem_down_write_failed+0xe/0x10 kernel/locking/rwsem-xadd.c:595
>   call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117
>   __down_write arch/x86/include/asm/rwsem.h:142 [inline]
>   down_write+0xa2/0x120 kernel/locking/rwsem.c:72
>   inode_lock include/linux/fs.h:713 [inline]
>   fat_fallocate+0x12d/0x320 fs/fat/file.c:249
>   vfs_fallocate+0x4b4/0x8d0 fs/open.c:319
>   ksys_fallocate+0x56/0x90 fs/open.c:342
>   __do_sys_fallocate fs/open.c:350 [inline]
>   __se_sys_fallocate fs/open.c:348 [inline]
>   __x64_sys_fallocate+0x97/0xf0 fs/open.c:348
>   do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x455979
> RSP: 002b:00007fe1b4f97c68 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
> RAX: ffffffffffffffda RBX: 00007fe1b4f986d4 RCX: 0000000000455979
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000016
> RBP: 000000000072bf50 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000001fffff R11: 0000000000000246 R12: 00000000ffffffff
> R13: 000000000000007e R14: 00000000006f3c70 R15: 0000000000000001
>
> Showing all locks held in the system:
> 2 locks held by kworker/u4:2/40:
>   #0: 0000000014018ef5 ((wq_completion)"writeback"){+.+.}, at:
> __write_once_size include/linux/compiler.h:215 [inline]
>   #0: 0000000014018ef5 ((wq_completion)"writeback"){+.+.}, at:
> arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>   #0: 0000000014018ef5 ((wq_completion)"writeback"){+.+.}, at: atomic64_set
> include/asm-generic/atomic-instrumented.h:40 [inline]
>   #0: 0000000014018ef5 ((wq_completion)"writeback"){+.+.}, at:
> atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
>   #0: 0000000014018ef5 ((wq_completion)"writeback"){+.+.}, at: set_work_data
> kernel/workqueue.c:617 [inline]
>   #0: 0000000014018ef5 ((wq_completion)"writeback"){+.+.}, at:
> set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
>   #0: 0000000014018ef5 ((wq_completion)"writeback"){+.+.}, at:
> process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
>   #1: 0000000042b710aa ((work_completion)(&(&wb->dwork)->work)){+.+.}, at:
> process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
> 2 locks held by khungtaskd/892:
>   #0: 0000000003100faf (rcu_read_lock){....}, at:
> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
>   #0: 0000000003100faf (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60
> kernel/hung_task.c:249
>   #1: 00000000110d22d7 (tasklist_lock){.+.+}, at:
> debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470
> 2 locks held by getty/4526:
>   #0: 00000000a0a0ce51 (&tty->ldisc_sem){++++}, at:
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>   #1: 0000000031b704da (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
> 2 locks held by getty/4527:
>   #0: 000000002be52f05 (&tty->ldisc_sem){++++}, at:
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>   #1: 00000000ddbf69c5 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
> 2 locks held by getty/4528:
>   #0: 000000006105deca (&tty->ldisc_sem){++++}, at:
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>   #1: 00000000bd3b5b98 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
> 2 locks held by getty/4529:
>   #0: 00000000d184409b (&tty->ldisc_sem){++++}, at:
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>   #1: 00000000d73f7bb9 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
> 2 locks held by getty/4530:
>   #0: 00000000096b0714 (&tty->ldisc_sem){++++}, at:
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>   #1: 00000000915cba6f (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
> 2 locks held by getty/4531:
>   #0: 00000000aba38cd7 (&tty->ldisc_sem){++++}, at:
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>   #1: 00000000db8a6329 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
> 2 locks held by getty/4532:
>   #0: 000000008ed47fa0 (&tty->ldisc_sem){++++}, at:
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>   #1: 00000000aeac4f11 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
> 2 locks held by syz-executor0/10251:
>   #0: 00000000175b9bfc (sb_writers#17){.+.+}, at: file_start_write
> include/linux/fs.h:2718 [inline]
>   #0: 00000000175b9bfc (sb_writers#17){.+.+}, at: vfs_fallocate+0x5be/0x8d0
> fs/open.c:318
>   #1: 00000000ae4afbc4 (&sb->s_type->i_mutex_key#19){+.+.}, at: inode_lock
> include/linux/fs.h:713 [inline]
>   #1: 00000000ae4afbc4 (&sb->s_type->i_mutex_key#19){+.+.}, at:
> fat_fallocate+0x12d/0x320 fs/fat/file.c:249
> 2 locks held by syz-executor0/10255:
>   #0: 00000000175b9bfc (sb_writers#17){.+.+}, at: sb_start_write
> include/linux/fs.h:1550 [inline]
>   #0: 00000000175b9bfc (sb_writers#17){.+.+}, at:
> do_sys_ftruncate+0x290/0x560 fs/open.c:200
>   #1: 00000000ae4afbc4 (&sb->s_type->i_mutex_key#19){+.+.}, at: inode_lock
> include/linux/fs.h:713 [inline]
>   #1: 00000000ae4afbc4 (&sb->s_type->i_mutex_key#19){+.+.}, at:
> do_truncate+0x197/0x2a0 fs/open.c:61
>
> =============================================
>
> NMI backtrace for cpu 0
> CPU: 0 PID: 892 Comm: khungtaskd Not tainted 4.17.0-rc2+ #22
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x1b9/0x294 lib/dump_stack.c:113
>   nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103
>   nmi_trigger_cpumask_backtrace+0x151/0x192 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+0xc10/0xf60 kernel/hung_task.c:249
>   kthread+0x345/0x410 kernel/kthread.c:238
>   ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
> Sending NMI from CPU 0 to CPUs 1:
> NMI backtrace for cpu 1
> CPU: 1 PID: 10226 Comm: syz-executor0 Not tainted 4.17.0-rc2+ #22
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:783
> [inline]
> RIP: 0010:lock_acquire+0x257/0x520 kernel/locking/lockdep.c:3923
> RSP: 0018:ffff8801b3126a08 EFLAGS: 00000286
> RAX: dffffc0000000000 RBX: 1ffff10036624d46 RCX: 0000000000000000
> RDX: 1ffffffff11a315d RSI: ffff8801af0fe978 RDI: 0000000000000286
> RBP: ffff8801b3126af8 R08: 0000000000000008 R09: 0000000000000003
> R10: ffff8801af0fe9f0 R11: ffff8801af0fe140 R12: ffff8801af0fe140
> R13: 0000000000000002 R14: 0000000000000000 R15: 0000000000000000
> FS:  00007fe1b4fb9700(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffffffff600400 CR3: 00000001af5f9000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   rcu_lock_acquire include/linux/rcupdate.h:246 [inline]
>   rcu_read_lock include/linux/rcupdate.h:632 [inline]
>   find_get_entry+0x11a/0xb90 mm/filemap.c:1428
>   pagecache_get_page+0x116/0xe20 mm/filemap.c:1541
>   find_or_create_page include/linux/pagemap.h:322 [inline]
>   grow_dev_page fs/buffer.c:940 [inline]
>   grow_buffers fs/buffer.c:1009 [inline]
>   __getblk_slow fs/buffer.c:1036 [inline]
>   __getblk_gfp+0x39e/0xaf0 fs/buffer.c:1313
>   __bread_gfp+0x2d/0x310 fs/buffer.c:1347
>   sb_bread include/linux/buffer_head.h:309 [inline]
>   __fat_write_inode+0x33f/0xb40 fs/fat/inode.c:845
>   fat_write_inode+0x97/0x180 fs/fat/inode.c:894
>   write_inode fs/fs-writeback.c:1183 [inline]
>   __writeback_single_inode+0xf18/0x15c0 fs/fs-writeback.c:1382
>   writeback_single_inode+0x364/0x510 fs/fs-writeback.c:1436
>   sync_inode fs/fs-writeback.c:2470 [inline]
>   sync_inode_metadata+0x10b/0x160 fs/fs-writeback.c:2490
>   __generic_file_fsync+0x16f/0x200 fs/libfs.c:988
>   generic_file_fsync+0x77/0x120 fs/libfs.c:1018
>   fat_file_fsync+0x77/0x180 fs/fat/file.c:165
>   vfs_fsync_range+0x140/0x220 fs/sync.c:197
>   generic_write_sync include/linux/fs.h:2689 [inline]
>   generic_file_write_iter+0x5f1/0x850 mm/filemap.c:3296
>   call_write_iter include/linux/fs.h:1784 [inline]
>   new_sync_write fs/read_write.c:474 [inline]
>   __vfs_write+0x64d/0x960 fs/read_write.c:487
>   vfs_write+0x1f8/0x560 fs/read_write.c:549
>   ksys_write+0xf9/0x250 fs/read_write.c:598
>   __do_sys_write fs/read_write.c:610 [inline]
>   __se_sys_write fs/read_write.c:607 [inline]
>   __x64_sys_write+0x73/0xb0 fs/read_write.c:607
>   do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x455979
> RSP: 002b:00007fe1b4fb8c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007fe1b4fb96d4 RCX: 0000000000455979
> RDX: 0000000000000022 RSI: 0000000020000100 RDI: 0000000000000013
> RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 00000000000006cc R14: 00000000006fd3c0 R15: 0000000000000000
> Code: 00 00 00 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 5e 02 00 00 48 83 3d
> 60 6e 74 07 00 0f 84 c8 01 00 00 48 8b bd 20 ff ff ff 57 9d <0f> 1f 44 00
> 00 48 b8 00 00 00 00 00 fc ff df 48 01 c3 48 c7 03
> INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.207
> msecs
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
> into any tree, please reply to this email with:
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> To mark this as a duplicate of another syzbot report, please reply with:
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