[syzbot] [kernfs?] WARNING in __kernfs_new_node

[syzbot <syzbot+ed4cf6ba7dd6164eb4ff@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    ec039126b7fa Add linux-next specific files for 20260611
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1733d9ee580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d0d1fa2afcbce17c
dashboard link: https://syzkaller.appspot.com/bug?extid=ed4cf6ba7dd6164eb4ff
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/be809c32a471/disk-ec039126.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/13ea1053e3b5/vmlinux-ec039126.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1bcdab47ddc8/bzImage-ec039126.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ed4cf6ba7dd6164eb4ff@syzkaller.appspotmail.com

------------[ cut here ]------------
!atomic_read(&kn->count)
WARNING: fs/kernfs/dir.c:560 at kernfs_get fs/kernfs/dir.c:560 [inline], CPU#0: kworker/0:2/820
WARNING: fs/kernfs/dir.c:560 at __kernfs_new_node+0x8b8/0xa70 fs/kernfs/dir.c:704, CPU#0: kworker/0:2/820
Modules linked in:
CPU: 0 UID: 0 PID: 820 Comm: kworker/0:2 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: events request_firmware_work_func
RIP: 0010:kernfs_get fs/kernfs/dir.c:560 [inline]
RIP: 0010:__kernfs_new_node+0x8b8/0xa70 fs/kernfs/dir.c:704
Code: 08 e9 44 fb ff ff e8 77 2d 59 ff e8 e2 c6 27 ff e9 8f fa ff ff e8 68 2d 59 ff e8 a3 e0 c6 fe e9 26 fb ff ff e8 59 2d 59 ff 90 <0f> 0b 90 e9 d1 fc ff ff e8 db 55 d1 08 89 f9 80 e1 07 80 c1 03 38
RSP: 0018:ffffc90003bbf440 EFLAGS: 00010293
RAX: ffffffff826c9e47 RBX: 0000000000000000 RCX: ffff88802655dd00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003bbf598 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed10064cbc1f R12: ffff88803265e0f0
R13: 1ffff92000777e94 R14: dffffc0000000000 R15: ffff88805cc1b3c0
FS:  0000000000000000(0000) GS:ffff888125a6b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c272190 CR3: 000000003404a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 kernfs_new_node fs/kernfs/dir.c:751 [inline]
 kernfs_create_dir_ns+0xfe/0x230 fs/kernfs/dir.c:1120
 sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:73 [inline]
 kobject_add_internal+0x631/0xd10 lib/kobject.c:240
 kobject_add_varg lib/kobject.c:374 [inline]
 kobject_add+0x163/0x240 lib/kobject.c:426
 class_dir_create_and_add drivers/base/core.c:3300 [inline]
 get_device_parent+0x31d/0x3a0 drivers/base/core.c:3351
 device_add+0x2e1/0xb90 drivers/base/core.c:3681
 fw_load_sysfs_fallback drivers/base/firmware_loader/fallback.c:86 [inline]
 fw_load_from_user_helper drivers/base/firmware_loader/fallback.c:162 [inline]
 firmware_fallback_sysfs+0x2e4/0xa30 drivers/base/firmware_loader/fallback.c:238
 _request_firmware+0x1052/0x1780 drivers/base/firmware_loader/main.c:898
 request_firmware_work_func+0xba/0x2e0 drivers/base/firmware_loader/main.c:1162
 process_one_work+0x98b/0x1630 kernel/workqueue.c:3326
 process_scheduled_works kernel/workqueue.c:3409 [inline]
 worker_thread+0xb49/0x1140 kernel/workqueue.c:3490
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


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