[  187.392155] usb 4-1: USB disconnect, address 3
[  187.393750] option: option_instat_callback: error -108
[  187.394114] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
[  187.394143] option 4-1:1.0: device disconnected
[  187.394388] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
[  187.394425] option 4-1:1.1: device disconnected
[  187.485406] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
[  187.485414] IP: [<ffffffff81399802>] usb_autopm_do_interface+0x22/0x110
[  187.485424] PGD 4c103067 PUD 4c100067 PMD 0 
[  187.485429] Oops: 0000 [#1] SMP 
[  187.485432] last sysfs file: /sys/devices/pci0000:00/0000:00:1c.1/0000:0c:00.0/ieee80211/phy0/rfkill2/state
[  187.485436] CPU 1 
[  187.485438] Modules linked in: ppp_deflate zlib_deflate bsd_comp ppp_async crc_ccitt option usbserial usb_storage binfmt_misc vboxnetadp vboxnetflt vboxdrv coretemp lp snd_hda_codec_idt snd_hda_intel arc4 snd_hda_codec snd_pcm_oss snd_mixer_oss ecb snd_pcm snd_seq_dummy snd_seq_oss pcmcia snd_seq_midi iwl3945 snd_rawmidi iwlcore snd_seq_midi_event snd_seq snd_timer snd_seq_device mac80211 yenta_socket led_class snd rsrc_nonstatic soundcore joydev pcmcia_core snd_page_alloc nvidia(P) cfg80211 dell_wmi dell_laptop ppdev psmouse dcdbas serio_raw parport_pc parport sha256_generic aes_x86_64 aes_generic cbc tg3 dm_crypt fbcon tileblit font bitblit softcursor i915 drm i2c_algo_bit video output intel_agp
[  187.485495] Pid: 3971, comm: pppd Tainted: P           2.6.31-5-generic #24-Ubuntu Latitude D620                   
[  187.485498] RIP: 0010:[<ffffffff81399802>]  [<ffffffff81399802>] usb_autopm_do_interface+0x22/0x110
[  187.485503] RSP: 0018:ffff88004c0abcf8  EFLAGS: 00010282
[  187.485505] RAX: ffff88004c0aa000 RBX: 0000000000000000 RCX: ffff880075ab4000
[  187.485507] RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000
[  187.485510] RBP: ffff88004c0abd38 R08: ffff8800545b04e0 R09: 0000000000000000
[  187.485513] R10: 0000000000000009 R11: 0000000000000246 R12: ffff88005b1b5428
[  187.485515] R13: 90feeb0b0fc3c95b R14: 00000000ffffffff R15: ffff88007dbbe900
[  187.485518] FS:  00007f9c9d3e76f0(0000) GS:ffff8800019e5000(0000) knlGS:0000000000000000
[  187.485521] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  187.485523] CR2: 0000000000000030 CR3: 000000004c104000 CR4: 00000000000006a0
[  187.485526] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  187.485528] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[  187.485531] Process pppd (pid: 3971, threadinfo ffff88004c0aa000, task ffff8800629a4410)
[  187.485533] Stack:
[  187.485535]  ffff88004c0abd08 ffff88004c0abd18 ffff88004c07c9a0 ffff88005b1b53c0
[  187.485539] <0> ffff88005b1b5428 90feeb0b0fc3c95b 0000000000000000 ffff88007dbbe900
[  187.485543] <0> ffff88004c0abd48 ffffffff8139991e ffff88004c0abd78 ffffffffa0f0b0e1
[  187.485548] Call Trace:
[  187.485553]  [<ffffffff8139991e>] usb_autopm_put_interface+0xe/0x10
[  187.485562]  [<ffffffffa0f0b0e1>] serial_do_free+0x81/0x90 [usbserial]
[  187.485568]  [<ffffffffa0f0b185>] serial_close+0x95/0xc0 [usbserial]
[  187.485573]  [<ffffffff812eb9a9>] tty_release_dev+0x159/0x5f0
[  187.485579]  [<ffffffff81011545>] ? __setup_rt_frame+0x2c5/0x420
[  187.485582]  [<ffffffff810117df>] ? handle_signal+0x13f/0x290
[  187.485586]  [<ffffffff810119e5>] ? do_signal+0xb5/0x1c0
[  187.485589]  [<ffffffff812ebe59>] tty_release+0x19/0x30
[  187.485594]  [<ffffffff81119bf0>] __fput+0xf0/0x210
[  187.485597]  [<ffffffff81119d2d>] fput+0x1d/0x30
[  187.485600]  [<ffffffff81115fa8>] filp_close+0x58/0x90
[  187.485603]  [<ffffffff81116099>] sys_close+0xb9/0x110
[  187.485607]  [<ffffffff81011fc2>] system_call_fastpath+0x16/0x1b
[  187.485609] Code: 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 48 83 ec 40 48 89 5d d8 4c 89 65 e0 48 89 fb 4c 89 6d e8 4c 89 75 f0 41 89 f6 4c 89 7d f8 <4c> 8b 7f 30 4d 8d af 60 04 00 00 4d 8d a7 70 ff ff ff 4c 89 ef 
[  187.485645] RIP  [<ffffffff81399802>] usb_autopm_do_interface+0x22/0x110
[  187.485649]  RSP <ffff88004c0abcf8>
[  187.485651] CR2: 0000000000000030
[  187.485654] ---[ end trace 3e50a524fbb27fbf ]---