general protection fault in pegasus_probe

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    1f22d15c usb: gadget: add raw-gadget interface
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=129ce77ae00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8ccee2968018adcb
dashboard link: https://syzkaller.appspot.com/bug?extid=41b0e2cc7adc40d57974
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+41b0e2cc7adc40d57974@xxxxxxxxxxxxxxxxxxxxxxxxx

kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
CPU: 1 PID: 3279 Comm: kworker/1:7 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
RIP: 0010:workqueue_sysfs_unregister kernel/workqueue.c:5689 [inline]
RIP: 0010:destroy_workqueue+0x2e/0x6b0 kernel/workqueue.c:4349
Code: 49 89 fe 41 55 41 54 55 53 48 83 ec 08 e8 1a 7e 23 00 49 8d be 08 01  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 e0 05 00 00 49 8b 9e 08 01 00 00 48 85 db 74 19
RSP: 0018:ffff8881aed87178 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000ec45000
RDX: 0000000000000021 RSI: ffffffff811affe6 RDI: 0000000000000108
RBP: ffff8881d16e0000 R08: ffff8881d34a3100 R09: fffffbfff11aeca6
R10: fffffbfff11aeca5 R11: ffffffff88d7652f R12: ffff8881c6aa0000
R13: 00000000fffffffb R14: 0000000000000000 R15: 0000000000000008
FS:  0000000000000000(0000) GS:ffff8881db500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000207e0000 CR3: 00000001d9871000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 pegasus_dec_workqueue drivers/net/usb/pegasus.c:1130 [inline]
 pegasus_dec_workqueue drivers/net/usb/pegasus.c:1126 [inline]
 pegasus_probe+0x1071/0x15d0 drivers/net/usb/pegasus.c:1225
 usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
 really_probe+0x281/0x6d0 drivers/base/dd.c:548
 driver_probe_device+0x104/0x210 drivers/base/dd.c:721
 __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
 bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
 __device_attach+0x217/0x360 drivers/base/dd.c:894
 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
 device_add+0x1480/0x1c20 drivers/base/core.c:2487
 usb_set_configuration+0xe67/0x1740 drivers/usb/core/message.c:2023
 generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
 usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
 really_probe+0x281/0x6d0 drivers/base/dd.c:548
 driver_probe_device+0x104/0x210 drivers/base/dd.c:721
 __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
 bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
 __device_attach+0x217/0x360 drivers/base/dd.c:894
 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
 device_add+0x1480/0x1c20 drivers/base/core.c:2487
 usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2537
 hub_port_connect drivers/usb/core/hub.c:5184 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5324 [inline]
 port_event drivers/usb/core/hub.c:5470 [inline]
 hub_event+0x1e59/0x3860 drivers/usb/core/hub.c:5552
 process_one_work+0x92b/0x1530 kernel/workqueue.c:2264
 process_scheduled_works kernel/workqueue.c:2326 [inline]
 worker_thread+0x7ab/0xe20 kernel/workqueue.c:2412
 kthread+0x318/0x420 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace b659e9aea6e4f6c5 ]---
RIP: 0010:workqueue_sysfs_unregister kernel/workqueue.c:5689 [inline]
RIP: 0010:destroy_workqueue+0x2e/0x6b0 kernel/workqueue.c:4349
Code: 49 89 fe 41 55 41 54 55 53 48 83 ec 08 e8 1a 7e 23 00 49 8d be 08 01  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 e0 05 00 00 49 8b 9e 08 01 00 00 48 85 db 74 19
RSP: 0018:ffff8881aed87178 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000ec45000
RDX: 0000000000000021 RSI: ffffffff811affe6 RDI: 0000000000000108
RBP: ffff8881d16e0000 R08: ffff8881d34a3100 R09: fffffbfff11aeca6
R10: fffffbfff11aeca5 R11: ffffffff88d7652f R12: ffff8881c6aa0000
R13: 00000000fffffffb R14: 0000000000000000 R15: 0000000000000008
FS:  0000000000000000(0000) GS:ffff8881db500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000207e0000 CR3: 00000001d9871000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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