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Date:   Mon, 08 Nov 2021 03:24:26 -0800
Message-ID: <00000000000047624505d0453c58@google.com>
Subject: [syzbot] WARNING in kernfs_remove_by_name_ns (3)
From:   syzbot <syzbot+93cbdd0ab421adc5275d@syzkaller.appspotmail.com>
To:     gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, tj@kernel.org
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Precedence: bulk

Hello,

syzbot found the following issue on:

HEAD commit:    ce840177930f Merge tag 'defconfig-5.16' of git://git.kerne..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1516eb12b00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=647adc5a101c9bf3
dashboard link: https://syzkaller.appspot.com/bug?extid=93cbdd0ab421adc5275d
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+93cbdd0ab421adc5275d@syzkaller.appspotmail.com

------------[ cut here ]------------
kernfs: can not remove 'nr_tags', no directory
WARNING: CPU: 0 PID: 352 at fs/kernfs/dir.c:1535 kernfs_remove_by_name_ns+0x96/0xa0 fs/kernfs/dir.c:1535
Modules linked in:
CPU: 0 PID: 352 Comm: syz-executor.0 Not tainted 5.15.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:kernfs_remove_by_name_ns+0x96/0xa0 fs/kernfs/dir.c:1535
Code: 83 ff 48 c7 c7 20 7a b5 8b 41 bc fe ff ff ff e8 f0 d9 67 ff eb d9 e8 49 f9 83 ff 4c 89 e6 48 c7 c7 a0 64 9d 89 e8 a1 35 01 07 <0f> 0b 41 bc fe ff ff ff eb bb 41 57 41 56 41 55 49 89 d5 41 54 49
RSP: 0018:ffffc90004c8fa68 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffffffff8c206628 RCX: 0000000000000000
RDX: ffff88806f28ba00 RSI: ffffffff815f39c8 RDI: fffff52000991f3f
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000037c24
R10: ffffffff815ed7ae R11: 0000000000000000 R12: ffffffff89e2ae80
R13: 0000000000000000 R14: ffffffff89e2ada0 R15: dffffc0000000000
FS:  00007fe5eef0f700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7b90e723a4 CR3: 00000001e5ed8000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 kernfs_remove_by_name include/linux/kernfs.h:598 [inline]
 remove_files+0x96/0x1c0 fs/sysfs/group.c:28
 sysfs_remove_group+0x87/0x170 fs/sysfs/group.c:289
 sysfs_remove_groups fs/sysfs/group.c:313 [inline]
 sysfs_remove_groups+0x5c/0xa0 fs/sysfs/group.c:305
 __kobject_del+0x89/0x200 lib/kobject.c:611
 kobject_del lib/kobject.c:643 [inline]
 kobject_del+0x3c/0x60 lib/kobject.c:635
 blk_mq_unregister_hctx block/blk-mq-sysfs.c:183 [inline]
 blk_mq_unregister_hctx block/blk-mq-sysfs.c:172 [inline]
 blk_mq_sysfs_unregister+0x227/0x300 block/blk-mq-sysfs.c:302
 __blk_mq_update_nr_hw_queues block/blk-mq.c:4102 [inline]
 blk_mq_update_nr_hw_queues+0x48c/0xd30 block/blk-mq.c:4142
 nbd_start_device+0x1f2/0xdd0 drivers/block/nbd.c:1357
 nbd_start_device_ioctl drivers/block/nbd.c:1407 [inline]
 __nbd_ioctl drivers/block/nbd.c:1481 [inline]
 nbd_ioctl+0x5f3/0xb10 drivers/block/nbd.c:1521
 blkdev_ioctl+0x37a/0x800 block/ioctl.c:597
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl fs/ioctl.c:860 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
 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+0x44/0xae
RIP: 0033:0x7fe5f19baae9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe5eef0f188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe5f1ace020 RCX: 00007fe5f19baae9
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000005
RBP: 00007fe5f1a14f25 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd3b00747f R14: 00007fe5eef0f300 R15: 0000000000022000
 </TASK>


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