Re: [syzbot] general protection fault in blk_mq_free_rqs

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in kernfs_remove_by_name_ns

------------[ cut here ]------------
kernfs: can not remove 'nr_tags', no directory
WARNING: CPU: 0 PID: 5711 at fs/kernfs/dir.c:1662 kernfs_remove_by_name_ns+0x102/0x120 fs/kernfs/dir.c:1662
Modules linked in:
CPU: 0 PID: 5711 Comm: syz-executor.0 Not tainted 6.6.0-syzkaller-15957-g826c484166f0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
RIP: 0010:kernfs_remove_by_name_ns+0x102/0x120 fs/kernfs/dir.c:1662
Code: 05 54 ff e8 d0 bc 74 ff bb fe ff ff ff 89 d8 5b 5d 41 5c 41 5d c3 e8 bd bc 74 ff 4c 89 e6 48 c7 c7 a0 b0 20 8a e8 9e 1f 3b ff <0f> 0b eb d5 e8 05 1e c8 ff e9 60 ff ff ff e8 fb 1d c8 ff e9 27 ff
RSP: 0018:ffffc90003577a48 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8149ce16
RDX: ffff888019661dc0 RSI: ffffffff8149ce23 RDI: 0000000000000001
RBP: ffffffff8cd13840 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffffffff8a6a1200
R13: 0000000000000000 R14: ffffffff8a6a1120 R15: 0000000000000002
FS:  00007ff8f2c4e6c0(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff8f1b9d0b0 CR3: 0000000074800000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 kernfs_remove_by_name include/linux/kernfs.h:623 [inline]
 remove_files+0x96/0x1c0 fs/sysfs/group.c:28
 sysfs_remove_group+0x87/0x170 fs/sysfs/group.c:292
 sysfs_remove_groups fs/sysfs/group.c:316 [inline]
 sysfs_remove_groups+0x5c/0xa0 fs/sysfs/group.c:308
 __kobject_del+0x83/0x1e0 lib/kobject.c:592
 kobject_del lib/kobject.c:624 [inline]
 kobject_del+0x3b/0x60 lib/kobject.c:616
 blk_mq_unregister_hctx block/blk-mq-sysfs.c:155 [inline]
 blk_mq_unregister_hctx block/blk-mq-sysfs.c:144 [inline]
 blk_mq_sysfs_unregister_hctxs+0x24a/0x2d0 block/blk-mq-sysfs.c:283
 __blk_mq_update_nr_hw_queues block/blk-mq.c:4727 [inline]
 blk_mq_update_nr_hw_queues+0x8a3/0x1350 block/blk-mq.c:4773
 nbd_start_device+0x157/0xd70 drivers/block/nbd.c:1362
 nbd_start_device_ioctl drivers/block/nbd.c:1412 [inline]
 __nbd_ioctl drivers/block/nbd.c:1487 [inline]
 nbd_ioctl+0x553/0xcc0 drivers/block/nbd.c:1527
 blkdev_ioctl+0x2f2/0x750 block/ioctl.c:633
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl fs/ioctl.c:857 [inline]
 __x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7ff8f1a7ad39
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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff8f2c4e0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff8f1b9bf80 RCX: 00007ff8f1a7ad39
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000007
RBP: 00007ff8f2c4e120 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 000000000000000b R14: 00007ff8f1b9bf80 R15: 00007fffa28dad08
 </TASK>


Tested on:

commit:         826c4841 Merge tag '6.7-rc-smb3-server-part2' of git:/..
git tree:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=129ef91f680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=58c022b9cf7593c8
dashboard link: https://syzkaller.appspot.com/bug?extid=7295389ef2000630244b
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.