linux-kernel - Re: [syzbot] [kernfs?] INFO: task hung in fdget

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Message-ID: <cu7oc32pbuz42gsd3bsmwjns54bqhtlpdi5xlimnjx4rebp3yz@fps6oycum3rf>
Date: Tue, 22 Jul 2025 13:31:03 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: syzbot <syzbot+0ee1ef35cf7e70ce55d7@...kaller.appspotmail.com>
Cc: brauner@...nel.org, gregkh@...uxfoundation.org, jack@...e.cz, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, 
	tj@...nel.org, viro@...iv.linux.org.uk
Subject: Re: [syzbot] [kernfs?] INFO: task hung in fdget_pos

On Wed, Oct 09, 2024 at 03:20:22AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    fc20a3e57247 Merge tag 'for-linus-6.12a-rc2-tag' of git://..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=110fb307980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9775e9a1af839423
> dashboard link: https://syzkaller.appspot.com/bug?extid=0ee1ef35cf7e70ce55d7
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11d0a79f980000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/64ef5d6cfda3/disk-fc20a3e5.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/42c0ee676795/vmlinux-fc20a3e5.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/a3072d6383ea/bzImage-fc20a3e5.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/a8f928c45431/mount_0.gz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+0ee1ef35cf7e70ce55d7@...kaller.appspotmail.com
> 
> INFO: task syz.2.17:5434 blocked for more than 159 seconds.
>       Not tainted 6.12.0-rc1-syzkaller-00330-gfc20a3e57247 #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz.2.17        state:D stack:27424 pid:5434  tgid:5432  ppid:5316   flags:0x00000004
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5315 [inline]
>  __schedule+0x1843/0x4ae0 kernel/sched/core.c:6675
>  __schedule_loop kernel/sched/core.c:6752 [inline]
>  schedule+0x14b/0x320 kernel/sched/core.c:6767
>  schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6824
>  __mutex_lock_common kernel/locking/mutex.c:684 [inline]
>  __mutex_lock+0x6a7/0xd70 kernel/locking/mutex.c:752
>  fdget_pos+0x24e/0x320 fs/file.c:1160
>  ksys_read+0x7e/0x2b0 fs/read_write.c:703
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f993c77dff9
> RSP: 002b:00007f993d54e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> RAX: ffffffffffffffda RBX: 00007f993c936058 RCX: 00007f993c77dff9
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
> RBP: 00007f993c7f0296 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000001 R14: 00007f993c936058 R15: 00007fffb8436518
>  </TASK>
> INFO: task syz.3.18:5439 blocked for more than 167 seconds.
>       Not tainted 6.12.0-rc1-syzkaller-00330-gfc20a3e57247 #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz.3.18        state:D stack:27424 pid:5439  tgid:5436  ppid:5317   flags:0x00000004
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5315 [inline]
>  __schedule+0x1843/0x4ae0 kernel/sched/core.c:6675
>  __schedule_loop kernel/sched/core.c:6752 [inline]
>  schedule+0x14b/0x320 kernel/sched/core.c:6767
>  schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6824
>  __mutex_lock_common kernel/locking/mutex.c:684 [inline]
>  __mutex_lock+0x6a7/0xd70 kernel/locking/mutex.c:752
>  fdget_pos+0x24e/0x320 fs/file.c:1160
>  ksys_read+0x7e/0x2b0 fs/read_write.c:703
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f1134d7dff9
> RSP: 002b:00007f1135adc038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> RAX: ffffffffffffffda RBX: 00007f1134f36058 RCX: 00007f1134d7dff9
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
> RBP: 00007f1134df0296 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000001 R14: 00007f1134f36058 R15: 00007ffe6e122188
>  </TASK>
> INFO: task syz.4.19:5441 blocked for more than 168 seconds.
>       Not tainted 6.12.0-rc1-syzkaller-00330-gfc20a3e57247 #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz.4.19        state:D stack:27424 pid:5441  tgid:5438  ppid:5327   flags:0x00000004
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5315 [inline]
>  __schedule+0x1843/0x4ae0 kernel/sched/core.c:6675
>  __schedule_loop kernel/sched/core.c:6752 [inline]
>  schedule+0x14b/0x320 kernel/sched/core.c:6767
>  schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6824
>  __mutex_lock_common kernel/locking/mutex.c:684 [inline]
>  __mutex_lock+0x6a7/0xd70 kernel/locking/mutex.c:752
>  fdget_pos+0x24e/0x320 fs/file.c:1160
>  ksys_read+0x7e/0x2b0 fs/read_write.c:703
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f4c9ad7dff9
> RSP: 002b:00007f4c9bc43038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
> 
> If you want to overwrite report's subsystems, reply with:

Someone assigned this to bcachefs, and it's clearly not:

#syz set subsystems: fs kernfs