[  273.628970] BUG: unable to handle kernel NULL pointer dereference at   (null)
[  273.629693] IP: [<f84d8e6b>] drm_debugfs_remove_files+0x4b/0xa0 [drm]
[  273.630457] *pdpt = 0000000029f7f001 *pde = 0000000000000000 
[  273.631222] Oops: 0000 [#1] SMP 
[  273.631976] Modules linked in: bnep rfcomm bluetooth parport_pc ppdev binfmt_misc ip6t_LOG xt_hl ip6t_rt nf_conntrack_ipv6 dm_crypt nf_defrag_ipv6 ipt_REJECT xt_comment ipt_LOG xt_limit xt_tcpudp xt_addrtype xt_state ip6table_filter joydev ip6_tables nf_conntrack_netbios_ns nf_conntrack_broadcast snd_hda_codec_realtek nf_nat_ftp nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_conntrack_ftp nf_conntrack iptable_filter snd_hda_intel snd_hda_codec snd_hwdep ip_tables snd_pcm x_tables snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device r852 sm_common nand nand_ids psmouse nand_bch bch serio_raw nand_ecc mtd arc4 snd iwl3945 iwl_legacy mac80211 soundcore cfg80211 snd_page_alloc coretemp firewire_sbp2 lp parport nouveau ttm drm_kms_helper drm i2c_algo_bit mxm_wmi firewire_ohci sdhci_pci sdhci ahci firewire_core crc_itu_t libahci tg3 wmi video
[  273.632013] 
[  273.632013] Pid: 2362, comm: firefox Not tainted 3.0.0-13-generic-pae #22-Ubuntu LENOVO 0769AP2/IEL10
[  273.632013] EIP: 0060:[<f84d8e6b>] EFLAGS: 00210286 CPU: 0
[  273.632013] EIP is at drm_debugfs_remove_files+0x4b/0xa0 [drm]
[  273.632013] EAX: 00000000 EBX: 00000000 ECX: 00033fec EDX: f1a96184
[  273.632013] ESI: ed6e53e0 EDI: e9d93208 EBP: e9f99e2c ESP: e9f99e10
[  273.632013]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
[  273.632013] Process firefox (pid: 2362, ti=e9f98000 task=ee35bfc0 task.ti=e9f98000)
[  273.632013] Stack:
[  273.632013]  f1a96184 f1a96000 00000001 00000000 e9d93000 f6980000 f1969c00 e9f99e3c
[  273.632013]  f877d2f6 e9d93000 e9f99e84 e9f99e70 f8701cd8 e9d9300c e9f99e5c e9f99e5c
[  273.632013]  c1554548 f6980550 00000004 e9f99e7c f6980000 e9f99e84 f1969c00 40046443
[  273.632013] Call Trace:
[  273.632013]  [<f877d2f6>] nouveau_debugfs_channel_fini+0x46/0x70 [nouveau]
[  273.632013]  [<f8701cd8>] nouveau_channel_put_unlocked+0x58/0x170 [nouveau]
[  273.632013]  [<c1554548>] ? mutex_lock+0x18/0x40
[  273.632013]  [<f8701e0c>] nouveau_channel_put+0x1c/0x20 [nouveau]
[  273.632013]  [<f87023fd>] nouveau_ioctl_fifo_free+0x2d/0x40 [nouveau]
[  273.632013]  [<f84c6f40>] drm_ioctl+0x390/0x450 [drm]
[  273.632013]  [<f87023d0>] ? nouveau_channel_get+0xa0/0xa0 [nouveau]
[  273.632013]  [<c1105843>] ? free_pgtables+0xa3/0xe0
[  273.632013]  [<c1105301>] ? tlb_finish_mmu+0x11/0x40
[  273.632013]  [<c110b4a8>] ? unmap_region+0xc8/0xe0
[  273.632013]  [<c110b184>] ? remove_vma+0x44/0x60
[  273.632013]  [<c110b184>] ? remove_vma+0x44/0x60
[  273.632013]  [<f84c6bb0>] ? drm_copy_field+0x80/0x80 [drm]
[  273.632013]  [<c11433e9>] do_vfs_ioctl+0x79/0x2d0
[  273.632013]  [<c11436af>] sys_ioctl+0x6f/0x80
[  273.632013]  [<c155c95f>] sysenter_do_call+0x12/0x28
[  273.632013] Code: 00 8d 91 84 01 00 00 90 8b 45 e8 8b b0 84 01 00 00 39 d6 8b 1e 75 0d eb 16 8d b4 26 00 00 00 00 89 de 89 c3 3b 7e 0c 74 1f 39 da <8b> 03 75 f1 83 45 f0 01 83 c7 10 8b 45 ec 39 45 f0 75 ca 83 c4 
[  273.632013] EIP: [<f84d8e6b>] drm_debugfs_remove_files+0x4b/0xa0 [drm] SS:ESP 0068:e9f99e10
[  273.632013] CR2: 0000000000000000
[  273.675877] ---[ end trace ac13eaba68b8e23e ]---