Crash on device disconnection

[MT00x]

The driver works quiet well until the USB device is disconnected, this cause a kernel error and reboot is needed to make device works again.

Kernel version: 4.14.79

usb 1-2: USB disconnect, device number 3
Internal error: Oops - undefined instruction: 0 [#1] ARM
Modules linked in: mt7601u mt7601Uap(O) rt2800usb rt2800lib rt2x00usb rt2x00lib mac80211 cfg80211 rfkill [last unloaded: mt7601u]
CPU: 0 PID: 203 Comm: kworker/0:1 Tainted: G           O    4.14.79 #1
Hardware name: Atmel AT91SAM9
Workqueue: usb_hub_wq hub_event
task: cf8f3820 task.stack: cf942000
PC is at free_netdev+0xc8/0xd0
LR is at pcpu_chunk_slot+0x3c/0x58
pc : [<c044552c>]    lr : [<c0185af8>]    psr: 80000013
sp : cf943ce8  ip : cf943c70  fp : cf943d04
r10: cf258274  r9 : cf258a00  r8 : bf2686cc
r7 : cf22e800  r6 : cde2683c  r5 : cde26800  r4 : cde267e4
r3 : 00000002  r2 : 00000000  r1 : 00008000  r0 : 0000000c
Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 0005317f  Table: 2f238000  DAC: 00000053
Process kworker/0:1 (pid: 203, stack limit = 0xcf942190)
Stack: (0xcf943ce8 to 0xcf944000)
3ce0:                   cde26800 d1002000 c072ab34 cf22e800 cf943d1c cf943d08
3d00: bf23c0e8 c0445474 00000000 d1002000 cf943d4c cf943d20 bf24a760 bf23c0d0
3d20: cf943d2c 00000000 c03780c0 cde26800 cf258220 cf258220 bf2686cc cf258200
3d40: cf943d8c cf943d50 c037a690 bf24a6bc ffffffed cf22e870 cf22e800 00000000
3d60: 00000034 cf258220 cf258254 bf2686cc 00000000 00000034 cf258a00 cf258274
3d80: cf943db4 cf943d90 c02f57a0 c037a628 cf258220 c091e0dc cf9e434c cf22e870
3da0: c0953b44 cf258a00 cf943dc4 cf943db8 c02f5858 c02f5650 cf943de4 cf943dc8
3dc0: c02f440c c02f5850 cf258220 cf258274 cf258228 cf22e870 cf943e24 cf943de8
3de0: c02f1250 c02f4330 c037eda4 c02f13d8 00000188 00000008 cf943e24 cf22e800
3e00: 00000000 00000001 cf170400 cf258200 cf258a00 00000100 cf943e4c cf943e28
3e20: c0378168 c02f109c 00000000 cf22e800 cf22e870 cf22e8a4 cf172200 cf258a00
3e40: cf943e84 cf943e50 c036f5bc c03780e4 cf943e84 cf943e60 c036d1f8 00000000
3e60: 00000002 00000002 cf1726fc cf170000 40000001 00000100 cf943f04 cf943e88
3e80: c0371044 c036f518 cf943ed2 00000000 00000009 cf17238c cf1700a4 cf172800
3ea0: cf170400 00000000 00000003 cf170000 cf172638 cf17238c cf172208 cf172630
3ec0: cf172820 cf17262c cf172200 cf172600 00030100 00000000 c0909f50 cf1726fc
3ee0: cf91e200 cffde300 00000000 c0909544 00000000 00000008 cf943f3c cf943f08
3f00: c0124be0 c03709ec c0909558 c090eac0 c0909544 cf91e200 c0909544 ffffe000
3f20: c0909558 c090eac0 cf91e218 00000008 cf943f74 cf943f40 c0124e48 c0124a14
3f40: cf825e8c cf91e200 c0124df0 cf04a780 cf9b3920 cf942000 cf825e8c cf91e200
3f60: c0124df0 cf04a798 cf943fac cf943f78 c012a678 c0124e00 00000000 00000000
3f80: cf943fac cf9b3920 c012a55c 00000000 00000000 00000000 00000000 00000000
3fa0: 00000000 cf943fb0 c01027a0 c012a56c 00000000 00000000 00000000 00000000
3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
3fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
Backtrace:
[<c0445464>] (free_netdev) from [<bf23c0e8>] (RtmpOSNetDevFree+0x28/0x2c [mt7601Uap])
 r7:cf22e800 r6:c072ab34 r5:d1002000 r4:cde26800
[<bf23c0c0>] (RtmpOSNetDevFree [mt7601Uap]) from [<bf24a760>] (rtusb_disconnect+0xb4/0xf0 [mt7601Uap])
 r5:d1002000 r4:00000000
[<bf24a6ac>] (rtusb_disconnect [mt7601Uap]) from [<c037a690>] (usb_unbind_interface+0x78/0x268)
 r7:cf258200 r6:bf2686cc r5:cf258220 r4:cf258220
[<c037a618>] (usb_unbind_interface) from [<c02f57a0>] (device_release_driver_internal+0x160/0x200)
 r10:cf258274 r9:cf258a00 r8:00000034 r7:00000000 r6:bf2686cc r5:cf258254
 r4:cf258220
[<c02f5640>] (device_release_driver_internal) from [<c02f5858>] (device_release_driver+0x18/0x1c)
 r9:cf258a00 r8:c0953b44 r7:cf22e870 r6:cf9e434c r5:c091e0dc r4:cf258220
[<c02f5840>] (device_release_driver) from [<c02f440c>] (bus_remove_device+0xec/0x120)
[<c02f4320>] (bus_remove_device) from [<c02f1250>] (device_del+0x1c4/0x33c)
 r7:cf22e870 r6:cf258228 r5:cf258274 r4:cf258220
[<c02f108c>] (device_del) from [<c0378168>] (usb_disable_device+0x94/0x1d8)
 r10:00000100 r9:cf258a00 r8:cf258200 r7:cf170400 r6:00000001 r5:00000000
 r4:cf22e800
[<c03780d4>] (usb_disable_device) from [<c036f5bc>] (usb_disconnect+0xb4/0x210)
 r9:cf258a00 r8:cf172200 r7:cf22e8a4 r6:cf22e870 r5:cf22e800 r4:00000000
[<c036f508>] (usb_disconnect) from [<c0371044>] (hub_event+0x668/0x1154)
 r10:00000100 r9:40000001 r8:cf170000 r7:cf1726fc r6:00000002 r5:00000002
 r4:00000000
[<c03709dc>] (hub_event) from [<c0124be0>] (process_one_work+0x1dc/0x3ec)
 r10:00000008 r9:00000000 r8:c0909544 r7:00000000 r6:cffde300 r5:cf91e200
 r4:cf1726fc
[<c0124a04>] (process_one_work) from [<c0124e48>] (worker_thread+0x58/0x5dc)
 r10:00000008 r9:cf91e218 r8:c090eac0 r7:c0909558 r6:ffffe000 r5:c0909544
 r4:cf91e200
[<c0124df0>] (worker_thread) from [<c012a678>] (kthread+0x11c/0x134)
 r10:cf04a798 r9:c0124df0 r8:cf91e200 r7:cf825e8c r6:cf942000 r5:cf9b3920
 r4:cf04a780
[<c012a55c>] (kthread) from [<c01027a0>] (ret_from_fork+0x14/0x34)
 r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:c012a55c
 r4:cf9b3920
Code: e1d300b2 e0450000 ebf4f940 e89da8f0 (e7f001f2)
---[ end trace 6e284616c2a0c898 ]---
Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 17 [#2] ARM
Modules linked in: mt7601u mt7601Uap(O) rt2800usb rt2800lib rt2x00usb rt2x00lib mac80211 cfg80211 rfkill [last unloaded: mt7601u]
CPU: 0 PID: 7 Comm: ksoftirqd/0 Tainted: G      D    O    4.14.79 #1
Hardware name: Atmel AT91SAM9
task: cf828420 task.stack: cf83a000
PC is at in_dev_finish_destroy+0x44/0xac
LR is at in_dev_finish_destroy+0x34/0xac
pc : [<c04ae6f8>]    lr : [<c04ae6e8>]    psr: 80000093
sp : cf83be90  ip : cf83be90  fp : cf83bea4
r10: c0933d20  r9 : 00000100  r8 : ffffe000
r7 : c0148258  r6 : ffffe000  r5 : cde26800  r4 : cde2fa00
r3 : 80000093  r2 : 00000000  r1 : 80000013  r0 : 00000000
Flags: Nzcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 0005317f  Table: 2f25c000  DAC: 00000053
Process ksoftirqd/0 (pid: 7, stack limit = 0xcf83a190)
Stack: (0xcf83be90 to 0xcf83c000)
be80:                                     cf1eed38 00000fff cf83beb4 cf83bea8
bea0: c04ae7f0 c04ae6c4 cf83bed4 cf83beb8 c0148258 c04ae7c8 c090ea9c 0000000a
bec0: 00000200 c0933d44 cf83beec cf83bed8 c01482cc c01481fc 00000009 0000000a
bee0: cf83bf3c cf83bef0 c0101564 c01482c4 cf83bf34 cf83bf00 c052b798 04208040
bf00: 0000aa55 0000000a c0933d20 40000009 ffffe000 cf80bf40 ffffe000 00000000
bf20: c0908268 00000001 c012de58 cf811858 cf83bf4c cf83bf40 c0112f84 c01014d0
bf40: cf83bf74 cf83bf50 c012df5c c0112f58 cf811840 cf80bf20 cf83a000 cf821df4
bf60: cf80bf40 c012de58 cf83bfac cf83bf78 c012a678 c012de68 00000000 00000000
bf80: cf83bfac cf80bf20 c012a55c 00000000 00000000 00000000 00000000 00000000
bfa0: 00000000 cf83bfb0 c01027a0 c012a56c 00000000 00000000 00000000 00000000
bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
bfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
Backtrace:
[<c04ae6b4>] (in_dev_finish_destroy) from [<c04ae7f0>] (in_dev_rcu_put+0x38/0x3c)
 r5:00000fff r4:cf1eed38
[<c04ae7b8>] (in_dev_rcu_put) from [<c0148258>] (__rcu_process_callbacks+0x6c/0xc8)
[<c01481ec>] (__rcu_process_callbacks) from [<c01482cc>] (rcu_process_callbacks+0x18/0x28)
 r7:c0933d44 r6:00000200 r5:0000000a r4:c090ea9c
[<c01482b4>] (rcu_process_callbacks) from [<c0101564>] (__do_softirq+0xa4/0x264)
 r5:0000000a r4:00000009
[<c01014c0>] (__do_softirq) from [<c0112f84>] (run_ksoftirqd+0x3c/0x5c)
 r10:cf811858 r9:c012de58 r8:00000001 r7:c0908268 r6:00000000 r5:ffffe000
 r4:cf80bf40
[<c0112f48>] (run_ksoftirqd) from [<c012df5c>] (smpboot_thread_fn+0x104/0x184)
[<c012de58>] (smpboot_thread_fn) from [<c012a678>] (kthread+0x11c/0x134)
 r9:c012de58 r8:cf80bf40 r7:cf821df4 r6:cf83a000 r5:cf80bf20 r4:cf811840
[<c012a55c>] (kthread) from [<c01027a0>] (ret_from_fork+0x14/0x34)
 r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:c012a55c
 r4:cf80bf20
Code: e10f1000 e3813080 e121f003 e5952248 (e5923000)
---[ end trace 6e284616c2a0c899 ]---
Kernel panic - not syncing: Fatal exception in interrupt
---[ end Kernel panic - not syncing: Fatal exception in interrupt

[MT00x]

Update:
the problem is somehow related to dchpcd daemon.
Stopping dhcpcd solve the issue when the device is disconnected.
Also adding
denyinterfaces ra0
to /etc/dhcpc.conf works.