general protection fault in cdev_del

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    69bbe8c7 usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=178e4526a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c309d28e15db39c5
dashboard link: https://syzkaller.appspot.com/bug?extid=67b2bd0e34f952d0321e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10dc5d54a00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17cae526a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+67b2bd0e34f952d0321e@xxxxxxxxxxxxxxxxxxxxxxxxx

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN PTI
CPU: 1 PID: 2486 Comm: kworker/1:2 Not tainted 5.2.0-rc1+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
RIP: 0010:cdev_del+0x22/0x90 fs/char_dev.c:592
Code: cf 0f 1f 80 00 00 00 00 55 48 89 fd 48 83 ec 08 e8 93 a5 d5 ff 48 8d  
7d 64 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48  
89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 4f 48
RSP: 0018:ffff8881d18e7218 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff8881d249a100 RCX: ffffffff820d879e
RDX: 000000000000000c RSI: ffffffff8167705d RDI: 0000000000000064
RBP: 0000000000000000 R08: ffff8881d18d1800 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8881d25c9100 R14: 0000000000000000 R15: ffff8881cc2a8070
FS:  0000000000000000(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f35af318000 CR3: 00000001cc182000 CR4: 00000000001406e0
Call Trace:
 tty_unregister_device drivers/tty/tty_io.c:3192 [inline]
 tty_unregister_device+0x10d/0x1a0 drivers/tty/tty_io.c:3187
 hso_serial_tty_unregister drivers/net/usb/hso.c:2245 [inline]
 hso_create_bulk_serial_device drivers/net/usb/hso.c:2682 [inline]
 hso_probe.cold+0xc8/0x120 drivers/net/usb/hso.c:2948
 usb_probe_interface+0x30b/0x7a0 drivers/usb/core/driver.c:361
 really_probe+0x287/0x660 drivers/base/dd.c:509
 driver_probe_device+0x104/0x210 drivers/base/dd.c:670
 __device_attach_driver+0x1c4/0x230 drivers/base/dd.c:777
 bus_for_each_drv+0x15e/0x1e0 drivers/base/bus.c:454
 __device_attach+0x217/0x360 drivers/base/dd.c:843
 bus_probe_device+0x1e6/0x290 drivers/base/bus.c:514
 device_add+0xae6/0x1700 drivers/base/core.c:2111
 usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
 generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
 usb_probe_device+0xa2/0x100 drivers/usb/core/driver.c:266
 really_probe+0x287/0x660 drivers/base/dd.c:509
 driver_probe_device+0x104/0x210 drivers/base/dd.c:670
 __device_attach_driver+0x1c4/0x230 drivers/base/dd.c:777
 bus_for_each_drv+0x15e/0x1e0 drivers/base/bus.c:454
 __device_attach+0x217/0x360 drivers/base/dd.c:843
 bus_probe_device+0x1e6/0x290 drivers/base/bus.c:514
 device_add+0xae6/0x1700 drivers/base/core.c:2111
 usb_new_device.cold+0x8c1/0x1016 drivers/usb/core/hub.c:2534
 hub_port_connect drivers/usb/core/hub.c:5089 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
 port_event drivers/usb/core/hub.c:5350 [inline]
 hub_event+0x1adc/0x35a0 drivers/usb/core/hub.c:5432
 process_one_work+0x90a/0x1580 kernel/workqueue.c:2268
 worker_thread+0x96/0xe20 kernel/workqueue.c:2414
 kthread+0x30e/0x420 kernel/kthread.c:254
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace 3b56fa5a205cba42 ]---
RIP: 0010:cdev_del+0x22/0x90 fs/char_dev.c:592
Code: cf 0f 1f 80 00 00 00 00 55 48 89 fd 48 83 ec 08 e8 93 a5 d5 ff 48 8d  
7d 64 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48  
89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 4f 48
RSP: 0018:ffff8881d18e7218 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff8881d249a100 RCX: ffffffff820d879e
RDX: 000000000000000c RSI: ffffffff8167705d RDI: 0000000000000064
RBP: 0000000000000000 R08: ffff8881d18d1800 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8881d25c9100 R14: 0000000000000000 R15: ffff8881cc2a8070
FS:  0000000000000000(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f35af318000 CR3: 00000001cc182000 CR4: 00000000001406e0


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