[mythtv-users] Null pointer dereference

[Ryan Stuart]

Hi All,

After applying Ubuntu updates to my mythbuntu box (one of which was
the new 2.6.24-19 kernel image), I can no longer watch TV (as a side
note, this is really annoying because I literally only just got my
remote working :( ). Every time I try to watch tv, it says it can't
connect to the backend.

So I decided to run the myth-setup to make sure everything was ok.
When I try to add, edit a capture card, myth-setup hangs. The
following also appears in syslog:

Sep 29 20:20:01 danny /USR/SBIN/CRON[6517]: (root) CMD ([ -x
/etc/init.d/mythtv-status ] && /etc/init.d/mythtv-status reload >
/dev/null)
Sep 29 20:21:24 danny kernel: [  654.386509] Unable to handle kernel
NULL pointer dereference at 0000000000000000 RIP:
Sep 29 20:21:24 danny kernel: [  654.386520]
[dvb_core:dvb_frontend_open+0x230/0x2a0]
:dvb_core:dvb_frontend_open+0x230/0x2a0
Sep 29 20:21:24 danny kernel: [  654.386542] PGD 1ddec067 PUD 1ddc9067 PMD 0
Sep 29 20:21:24 danny kernel: [  654.386547] Oops: 0000 [1] SMP
Sep 29 20:21:24 danny kernel: [  654.386550] CPU 0
Sep 29 20:21:24 danny kernel: [  654.386552] Modules linked in:
af_packet ipv6 cpufreq_powersave cpufreq_conservative cpufreq_ondemand
cpufreq_userspace cpufreq_stats freq_table video output container sbs
sbshc dock battery iptable_filter ip_tables x_tables ac sbp2 lp mt2266
lirc_imon(F) lirc_dev dvb_usb_dib0700 dib7000p dib7000m dvb_usb
dvb_core joydev dib3000mc dibx000_common dib0070 saa7134_alsa
snd_hda_intel snd_pcm_oss snd_mixer_oss snd_hwdep snd_seq_dummy
snd_pcm snd_page_alloc snd_seq_oss snd_seq_midi snd_rawmidi
snd_seq_midi_event saa7134 snd_seq compat_ioctl32 snd_timer
snd_seq_device videobuf_dma_sg videobuf_core ir_kbd_i2c snd ir_common
i2c_nforce2 videodev nvidia(P) v4l2_common v4l1_compat button psmouse
serio_raw shpchp pci_hotplug soundcore i2c_core parport_pc parport
evdev k8temp pcspkr ext3 jbd mbcache usb_storage sg sd_mod usbhid hid
libusual sata_nv pata_amd pata_acpi floppy ohci1394 ieee1394 forcedeth
ata_generic ohci_hcd ehci_hcd libata scsi_mod usbcore thermal
processor fan fbcon tileblit
Sep 29 20:21:24 danny kernel: ont bitblit softcursor fuse
Sep 29 20:21:24 danny kernel: [  654.386611] Pid: 6704, comm:
mythtv-setup.re Tainted: PF       2.6.24-19-generic #1
Sep 29 20:21:24 danny kernel: [  654.386614] RIP:
0010:[dvb_core:dvb_frontend_open+0x230/0x2a0]
[dvb_core:dvb_frontend_open+0x230/0x2a0]
:dvb_core:dvb_frontend_open+0x230/0x2a0
Sep 29 20:21:24 danny kernel: [  654.386623] RSP:
0018:ffff81001dce1db8  EFLAGS: 00010246
Sep 29 20:21:24 danny kernel: [  654.386624] RAX: 0000000000000000
RBX: 0000000000000000 RCX: ffff81003ab24de0
Sep 29 20:21:24 danny kernel: [  654.386626] RDX: ffffffff88c03f45
RSI: ffff81003ce96000 RDI: ffffffff88bff3a0
Sep 29 20:21:24 danny kernel: [  654.386628] RBP: ffff81003ce96000
R08: ffff81003b8cedb0 R09: 0000000000000000
Sep 29 20:21:24 danny kernel: [  654.386630] R10: 0000000000000000
R11: ffff81003bf76db8 R12: ffff81003b19c800
Sep 29 20:21:24 danny kernel: [  654.386632] R13: ffff810010078240
R14: ffff81003ab24de0 R15: ffff81003b19c800
Sep 29 20:21:24 danny kernel: [  654.386635] FS:
00007f0ea20de7c0(0000) GS:ffffffff805b9000(0000)
knlGS:0000000000000000
Sep 29 20:21:24 danny kernel: [  654.386637] CS:  0010 DS: 0000 ES:
0000 CR0: 000000008005003b
Sep 29 20:21:24 danny kernel: [  654.386638] CR2: 0000000000000000
CR3: 000000001ddd5000 CR4: 00000000000006e0
Sep 29 20:21:24 danny kernel: [  654.386640] DR0: 0000000000000000
DR1: 0000000000000000 DR2: 0000000000000000
Sep 29 20:21:24 danny kernel: [  654.386642] DR3: 0000000000000000
DR6: 00000000ffff0ff0 DR7: 0000000000000400
Sep 29 20:21:24 danny kernel: [  654.386644] Process mythtv-setup.re
(pid: 6704, threadinfo ffff81001dce0000, task ffff810023b9f7a0)
Sep 29 20:21:24 danny kernel: [  654.386646] Stack:  0000000000000000
ffff81003bcc60d0 ffff81003b19c9b0 0000000000000000
Sep 29 20:21:24 danny kernel: [  654.386651]  ffff810010078240
ffffffff88c0d120 ffff81003bcc60d0 ffff810010078240
Sep 29 20:21:24 danny kernel: [  654.386654]  ffffffff802b5dd0
ffffffff88bf76dc ffffffff88c0e020 0000000000000000
Sep 29 20:21:24 danny kernel: [  654.386657] Call Trace:
Sep 29 20:21:24 danny kernel: [  654.386673]  [chrdev_open+0x0/0x1d0]
chrdev_open+0x0/0x1d0
Sep 29 20:21:24 danny kernel: [  654.386680]
[dvb_core:dvb_device_open+0xcc/0x140]
:dvb_core:dvb_device_open+0xcc/0x140
Sep 29 20:21:24 danny kernel: [  654.386685]  [chrdev_open+0xc1/0x1d0]
chrdev_open+0xc1/0x1d0
Sep 29 20:21:24 danny kernel: [  654.386696]
[__dentry_open+0xdb/0x200] __dentry_open+0xdb/0x200
Sep 29 20:21:24 danny kernel: [  654.386705]  [do_filp_open+0x3a/0x50]
do_filp_open+0x3a/0x50
Sep 29 20:21:24 danny kernel: [  654.386717]
[get_unused_fd_flags+0x77/0x120] get_unused_fd_flags+0x77/0x120
Sep 29 20:21:24 danny kernel: [  654.386726]  [do_sys_open+0x5a/0xf0]
do_sys_open+0x5a/0xf0
Sep 29 20:21:24 danny kernel: [  654.386734]  [system_call+0x7e/0x83]
system_call+0x7e/0x83
Sep 29 20:21:24 danny kernel: [  654.386747]
Sep 29 20:21:24 danny kernel: [  654.386748]
Sep 29 20:21:24 danny kernel: [  654.386748] Code: 8b 08 31 c0 e8 17
56 65 f7 48 3d 00 f0 ff ff 77 1d 48 89 c7
Sep 29 20:21:24 danny kernel: [  654.386755] RIP
[dvb_core:dvb_frontend_open+0x230/0x2a0]
:dvb_core:dvb_frontend_open+0x230/0x2a0
Sep 29 20:21:24 danny kernel: [  654.386763]  RSP <ffff81001dce1db8>
Sep 29 20:21:24 danny kernel: [  654.386765] CR2: 0000000000000000
Sep 29 20:21:24 danny kernel: [  654.386773] ---[ end trace
b58afee20014b695 ]---

Obviously a bug somewhere in the kernel I guess? Any idea where to go
from here? The obvious solution to me was to move back to an earlier
kernel image. But the mythbuntu-desktop depends on the meta packages
in Ubuntu for the latest kernel image, headers etc. which in turn
obviously depend on the latest kernel and I don't know enough about
the packaging system to get around that. Any ideas?

Cheers