syzbot

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refcount_t: addition on 0; use-after-free.
WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x111/0x130 lib/refcount.c:25, CPU#0: kworker/0:0/9
Modules linked in:
CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: usb_hub_wq hub_event
RIP: 0010:refcount_warn_saturate+0x111/0x130 lib/refcount.c:25
Code: cc e8 43 b5 e2 fe 48 8d 3d 7c 24 25 08 67 48 0f b9 3a e8 32 b5 e2 fe 5b 5d e9 8b 52 a0 04 e8 26 b5 e2 fe 48 8d 3d 6f 24 25 08 <67> 48 0f b9 3a e8 15 b5 e2 fe 5b 5d c3 cc cc cc cc 48 89 df e8 a6
RSP: 0018:ffffc9000009ef28 EFLAGS: 00010283
RAX: 000000000003ddec RBX: ffff88810a3a1de8 RCX: ffffc900113a0000
RDX: 0000000000100000 RSI: ffffffff82d00d5a RDI: ffffffff8af531d0
RBP: 0000000000000002 R08: 0000000000000005 R09: 0000000000000004
R10: 0000000000000002 R11: 0000000000000000 R12: ffff88813bb78000
R13: ffff88810a3a1de8 R14: 0000000000000000 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8882686a8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000036c0 CR3: 0000000128d7e000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 __refcount_add include/linux/refcount.h:289 [inline]
 __refcount_inc include/linux/refcount.h:366 [inline]
 refcount_inc include/linux/refcount.h:383 [inline]
 get_task_struct include/linux/sched/task.h:116 [inline]
 kthread_stop+0x5cd/0x640 kernel/kthread.c:754
 rsi_kill_thread drivers/net/wireless/rsi/rsi_common.h:78 [inline]
 rsi_91x_deinit+0x102/0x1f0 drivers/net/wireless/rsi/rsi_91x_main.c:405
 rsi_probe+0xd27/0x1aa0 drivers/net/wireless/rsi/rsi_91x_usb.c:861
 usb_probe_interface+0x303/0x8f0 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:631 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:709
 __driver_probe_device+0x22e/0x480 drivers/base/dd.c:871
 driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:901
 __device_attach_driver+0x1df/0x340 drivers/base/dd.c:1029
 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1101
 device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1156
 bus_probe_device+0x64/0x160 drivers/base/bus.c:613
 device_add+0x1210/0x1950 drivers/base/core.c:3706
 usb_set_configuration+0xd97/0x1c60 drivers/usb/core/message.c:2268
 usb_generic_driver_probe+0xa1/0xe0 drivers/usb/core/generic.c:250
 usb_probe_device+0xef/0x400 drivers/usb/core/driver.c:291
 call_driver_probe drivers/base/dd.c:631 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:709
 __driver_probe_device+0x22e/0x480 drivers/base/dd.c:871
 driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:901
 __device_attach_driver+0x1df/0x340 drivers/base/dd.c:1029
 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1101
 device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1156
 bus_probe_device+0x64/0x160 drivers/base/bus.c:613
 device_add+0x1210/0x1950 drivers/base/core.c:3706
 usb_new_device.cold+0x685/0x115c 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+0x314d/0x4af0 drivers/usb/core/hub.c:5953
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302
 process_scheduled_works kernel/workqueue.c:3385 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x69a/0xc80 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:	cc                   	int3
   1:	e8 43 b5 e2 fe       	call   0xfee2b549
   6:	48 8d 3d 7c 24 25 08 	lea    0x825247c(%rip),%rdi        # 0x8252489
   d:	67 48 0f b9 3a       	ud1    (%edx),%rdi
  12:	e8 32 b5 e2 fe       	call   0xfee2b549
  17:	5b                   	pop    %rbx
  18:	5d                   	pop    %rbp
  19:	e9 8b 52 a0 04       	jmp    0x4a052a9
  1e:	e8 26 b5 e2 fe       	call   0xfee2b549
  23:	48 8d 3d 6f 24 25 08 	lea    0x825246f(%rip),%rdi        # 0x8252499
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e8 15 b5 e2 fe       	call   0xfee2b549
  34:	5b                   	pop    %rbx
  35:	5d                   	pop    %rbp
  36:	c3                   	ret
  37:	cc                   	int3
  38:	cc                   	int3
  39:	cc                   	int3
  3a:	cc                   	int3
  3b:	48 89 df             	mov    %rbx,%rdi
  3e:	e8                   	.byte 0xe8
  3f:	a6                   	cmpsb  %es:(%rdi),%ds:(%rsi)