[syzbot] [btrfs?] WARNING in __alloc_workqueue (2)

[syzbot] [btrfs?] WARNING in __alloc_workqueue (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    a87737435cfa Add linux-next specific files for 20260608
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=178a7f2e580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=da47745f686dc823
dashboard link: https://syzkaller.appspot.com/bug?extid=f80c62f371ba6a1e7d79
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=170260ae580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=124f11b6580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/85d19fe6bb4e/disk-a8773743.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/30c683ce26e1/vmlinux-a8773743.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4db5027513d2/bzImage-a8773743.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f80c62f371ba6a1e7d79@syzkaller.appspotmail.com

usb 1-1: config 0 interface 0 altsetting 0 has an invalid descriptor for endpoint zero, skipping
usb 1-1: New USB device found, idVendor=0cf3, idProduct=9374, bcdDevice=bc.3b
usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 1-1: config 0 descriptor??
------------[ cut here ]------------
workqueue: ath6kl_wq is using neither WQ_PERCPU or WQ_UNBOUND. Setting WQ_PERCPU.
WARNING: kernel/workqueue.c:5856 at __alloc_workqueue+0x1d02/0x2070 kernel/workqueue.c:5855, CPU#0: kworker/0:3/5630
Modules linked in:
CPU: 0 UID: 0 PID: 5630 Comm: kworker/0:3 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: usb_hub_wq hub_event
RIP: 0010:__alloc_workqueue+0x1d07/0x2070 kernel/workqueue.c:5855
Code: e9 36 f9 ff ff e8 e9 89 37 00 e9 05 fb ff ff e8 df 89 37 00 e9 92 fb ff ff e8 d5 89 37 00 48 8d 3d 1e b7 43 0e 48 8b 74 24 20 <67> 48 0f b9 3a 81 cd 00 01 00 00 e9 88 e5 ff ff e8 b4 89 37 00 48
RSP: 0018:ffffc90004606bc8 EFLAGS: 00010293
RAX: ffffffff818e312b RBX: 0000000000000000 RCX: ffff8880342dbe00
RDX: 0000000000000000 RSI: ffff8880448f3d68 RDI: ffffffff8fd1e850
RBP: 0000000000000000 R08: ffff8880342dbe00 R09: 0000000000000002
R10: 0000000000000100 R11: 0000000000000102 R12: dffffc0000000000
R13: ffff8880448f3c00 R14: ffffc90004606ce0 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888125a76000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdb09f620f5 CR3: 0000000028f60000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 alloc_workqueue_va kernel/workqueue.c:5950 [inline]
 alloc_workqueue_noprof+0xe3/0x210 kernel/workqueue.c:5966
 ath6kl_usb_create drivers/net/wireless/ath/ath6kl/usb.c:639 [inline]
 ath6kl_usb_probe+0xaa/0x1580 drivers/net/wireless/ath/ath6kl/usb.c:1143
 usb_probe_interface+0x659/0xc70 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x267/0xaf0 drivers/base/dd.c:706
 __driver_probe_device+0x1e2/0x350 drivers/base/dd.c:868
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
 __device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
 bus_for_each_drv+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c8/0x450 drivers/base/dd.c:1098
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:620
 device_add+0x7ec/0xb90 drivers/base/core.c:3772
 usb_set_configuration+0x1a87/0x2110 drivers/usb/core/message.c:2268
 usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
 usb_probe_device+0x1c4/0x3b0 drivers/usb/core/driver.c:291
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x267/0xaf0 drivers/base/dd.c:706
 __driver_probe_device+0x1e2/0x350 drivers/base/dd.c:868
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
 __device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
 bus_for_each_drv+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c8/0x450 drivers/base/dd.c:1098
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:620
 device_add+0x7ec/0xb90 drivers/base/core.c:3772
 usb_new_device+0x9f8/0x16e0 drivers/usb/core/hub.c:2695
 hub_port_connect drivers/usb/core/hub.c:5567 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x2a49/0x4f60 drivers/usb/core/hub.c:5953
 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>
----------------
Code disassembly (best guess):
   0:	e9 36 f9 ff ff       	jmp    0xfffff93b
   5:	e8 e9 89 37 00       	call   0x3789f3
   a:	e9 05 fb ff ff       	jmp    0xfffffb14
   f:	e8 df 89 37 00       	call   0x3789f3
  14:	e9 92 fb ff ff       	jmp    0xfffffbab
  19:	e8 d5 89 37 00       	call   0x3789f3
  1e:	48 8d 3d 1e b7 43 0e 	lea    0xe43b71e(%rip),%rdi        # 0xe43b743
  25:	48 8b 74 24 20       	mov    0x20(%rsp),%rsi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	81 cd 00 01 00 00    	or     $0x100,%ebp
  35:	e9 88 e5 ff ff       	jmp    0xffffe5c2
  3a:	e8 b4 89 37 00       	call   0x3789f3
  3f:	48                   	rex.W


---
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