Extract from dmesg:

[32499.845341] usb 1-1.6: USB disconnect, device number 6
[32509.001659] usb 1-1.6: new full-speed USB device number 7 using ehci-pci
[32509.096558] usb 1-1.6: New USB device found, idVendor=0525, idProduct=a4a2
[32509.096561] usb 1-1.6: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[32509.096562] usb 1-1.6: Product: RNDIS/Ethernet Gadget
[32509.096563] usb 1-1.6: Manufacturer: Linux 2.6.32-ubi-stab033.19995-pxa with pxa27x_ud
[32509.276738] BUG: unable to handle kernel NULL pointer dereference at 0000000000000003
[32509.276761] IP: [<ffffffffc06b22a1>] usbnet_generic_cdc_bind+0x171/0x710 [cdc_ether]
[32509.276780] PGD 0 
[32509.276786] Oops: 0000 [#1] SMP 
[32509.276795] Modules linked in: cdc_ether(+) usbnet mii cfg80211 nfsv3 nfs_acl rpcsec_gss_krb5 auth_rpcgss nfsv4 nfs lockd grace fscache pci_stub vboxpci(OE) vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) binfmt_misc nls_iso8859_1 uas usb_storage intel_rapl x86_pkg_temp_thermal intel_powerclamp input_leds coretemp snd_hda_codec_realtek snd_hda_codec_hdmi snd_hda_codec_generic dcdbas kvm_intel kvm snd_hda_intel snd_hda_codec irqbypass snd_hda_core snd_hwdep crct10dif_pclmul crc32_pclmul snd_pcm aesni_intel snd_seq_midi snd_seq_midi_event aes_x86_64 lrw snd_rawmidi gf128mul glue_helper ablk_helper snd_seq cryptd serio_raw snd_seq_device snd_timer snd mei_me mei soundcore shpchp lpc_ich 8250_fintek mac_hid sunrpc parport_pc ppdev lp parport autofs4 hid_generic usbhid hid i915 i2c_algo_bit drm_kms_helper syscopyarea
[32509.276995]  sysfillrect sysimgblt e1000e psmouse fb_sys_fops ahci drm libahci ptp pps_core fjes video
[32509.277028] CPU: 1 PID: 19768 Comm: systemd-udevd Tainted: G           OE   4.4.0-21-generic #37-Ubuntu
[32509.277064] Hardware name: Dell Inc. OptiPlex 7020/08WKV3, BIOS A01 08/23/2014
[32509.277092] task: ffff8804097dee00 ti: ffff88000f410000 task.ti: ffff88000f410000
[32509.277109] RIP: 0010:[<ffffffffc06b22a1>]  [<ffffffffc06b22a1>] usbnet_generic_cdc_bind+0x171/0x710 [cdc_ether]
[32509.277132] RSP: 0018:ffff88000f4139b8  EFLAGS: 00010292
[32509.277144] RAX: 0000000000000000 RBX: ffff880341de6840 RCX: ffff8800c4cdc692
[32509.277159] RDX: ffff8800c4cdc692 RSI: ffff8800d3fb1400 RDI: ffff8803e9ce5800
[32509.277173] RBP: ffff88000f413a78 R08: ffff8800c4cdc672 R09: ffff88040e003900
[32509.277188] R10: ffff8803dba1f780 R11: 0000000000003b99 R12: ffff8800d3fb1400
[32509.277202] R13: 0000000000000000 R14: ffffffffc06b4068 R15: ffff880341de6938
[32509.277217] FS:  00007f96ef0778c0(0000) GS:ffff88041ea40000(0000) knlGS:0000000000000000
[32509.277234] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[32509.277246] CR2: 0000000000000003 CR3: 0000000098e76000 CR4: 00000000001406e0
[32509.277261] Stack:
[32509.277265]  ffff880341de62a0 ffff88000f413a08 ffffffff8172272e 0000000000000000
[32509.277283]  ffff8800c4cdc672 0000000000000000 0000000000000000 0000000000000000
[32509.277301]  0000000000000000 ffff8800c4cdc692 0000000000000000 ffff8800c4cdc677
[32509.277319] Call Trace:
[32509.277329]  [<ffffffff8172272e>] ? __hw_addr_add_ex+0x7e/0xe0
[32509.277342]  [<ffffffffc06b2859>] usbnet_cdc_bind+0x19/0x80 [cdc_ether]
[32509.277357]  [<ffffffffc06a13e0>] usbnet_probe+0x320/0x8c0 [usbnet]
[32509.277373]  [<ffffffff816154fd>] usb_probe_interface+0x1bd/0x300
[32509.277386]  [<ffffffff8154bd12>] driver_probe_device+0x222/0x4a0
[32509.277399]  [<ffffffff8154c014>] __driver_attach+0x84/0x90
[32509.277412]  [<ffffffff8154bf90>] ? driver_probe_device+0x4a0/0x4a0
[32509.277427]  [<ffffffff8154993c>] bus_for_each_dev+0x6c/0xc0
[32509.277440]  [<ffffffff8154b4ce>] driver_attach+0x1e/0x20
[32509.277452]  [<ffffffff8154b00b>] bus_add_driver+0x1eb/0x280
[32509.277465]  [<ffffffff8154c920>] driver_register+0x60/0xe0
[32509.277478]  [<ffffffff81613e44>] usb_register_driver+0x84/0x140
[32509.277491]  [<ffffffffc06b7000>] ? 0xffffffffc06b7000
[32509.277503]  [<ffffffffc06b701e>] cdc_driver_init+0x1e/0x1000 [cdc_ether]
[32509.277519]  [<ffffffff81002123>] do_one_initcall+0xb3/0x200
[32509.277533]  [<ffffffff811eaeb3>] ? kmem_cache_alloc_trace+0x183/0x1f0
[32509.277548]  [<ffffffff8118c163>] do_init_module+0x5f/0x1cf
[32509.277561]  [<ffffffff81109df7>] load_module+0x1667/0x1c00
[32509.277573]  [<ffffffff811063a0>] ? __symbol_put+0x60/0x60
[32509.277594]  [<ffffffff812126b0>] ? kernel_read+0x50/0x80
[32509.277606]  [<ffffffff8110a5d4>] SYSC_finit_module+0xb4/0xe0
[32509.277618]  [<ffffffff8110a61e>] SyS_finit_module+0xe/0x10
[32509.277630]  [<ffffffff818244f2>] entry_SYSCALL_64_fastpath+0x16/0x71
[32509.277643] Code: ff 48 8b 95 60 ff ff ff 48 8b 85 58 ff ff ff 48 8b 3b 48 89 93 f8 00 00 00 48 8b 55 88 48 89 83 00 01 00 00 48 89 93 08 01 00 00 <0f> b6 70 03 e8 76 0c f5 c0 48 89 83 10 01 00 00 48 8b 83 00 01 
[32509.277719] RIP  [<ffffffffc06b22a1>] usbnet_generic_cdc_bind+0x171/0x710 [cdc_ether]
[32509.277736]  RSP <ffff88000f4139b8>
[32509.277744] CR2: 0000000000000003
[32509.282629] ---[ end trace 5b59b3e9ec2e4364 ]---
[32589.181880] usb 1-1.6: USB disconnect, device number 7