V4L/DVB (9624): CVE-2008-5033: fix OOPS on tvaudio when controlling bass/treble

This bug were supposed to be fixed by 5ba2f67a,
where a call to NULL happens.

Not all tvaudio chips allow controlling bass/treble. So, the driver
has a table with a flag to indicate if the chip does support it.

Unfortunately, the handling of this logic were broken for a very long
time (probably since the first module version). Due to that, an OOPS
were generated for devices that don't support bass/treble.

This were the resulting OOPS message before the patch, with debug messages
enabled:

tvaudio' 1-005b: VIDIOC_S_CTRL
BUG: unable to handle kernel NULL pointer dereference at 00000000
IP: [<00000000>]
*pde = 22fda067 *pte = 00000000
Oops: 0000 [#1] SMP
Modules linked in: snd_hda_intel snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device
snd_pcm_oss snd_mixer_oss snd_pcm snd_timer snd_hwdep snd soundcore tuner_simple tuner_types tea5767 tuner
tvaudio bttv bridgebnep rfcomm l2cap bluetooth it87 hwmon_vid hwmon fuse sunrpc ipt_REJECT
nf_conntrack_ipv4 iptable_filter ip_tables ip6t_REJECT xt_tcpudp nf_conntrack_ipv6 xt_state nf_conntrack
ip6table_filter ip6_tables x_tables ipv6 dm_mirrordm_multipath dm_mod configfs videodev v4l1_compat
ir_common 8139cp compat_ioctl32 v4l2_common 8139too videobuf_dma_sg videobuf_core mii btcx_risc tveeprom
i915 button snd_page_alloc serio_raw drm pcspkr i2c_algo_bit i2c_i801 i2c_core iTCO_wdt
iTCO_vendor_support sr_mod cdrom sg ata_generic pata_acpi ata_piix libata sd_mod scsi_mod ext3 jbdmbcache
uhci_hcd ohci_hcd ehci_hcd [last unloaded: soundcore]

Pid: 15413, comm: qv4l2 Not tainted (2.6.25.14-108.fc9.i686 #1)
EIP: 0060:[<00000000>] EFLAGS: 00210246 CPU: 0
EIP is at 0x0
EAX: 00008000 EBX: ebd21600 ECX: e2fd9ec4 EDX: 00200046
ESI: f8c0f0c4 EDI: f8c0f0c4 EBP: e2fd9d50 ESP: e2fd9d2c
 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Process qv4l2 (pid: 15413, ti=e2fd9000 task=ebe44000 task.ti=e2fd9000)
Stack: f8c0c6ae e2ff2a00 00000d00 e2fd9ec4 ebc4e000 e2fd9d5c f8c0c448 00000000
       f899c12a e2fd9d5c f899c154 e2fd9d68 e2fd9d80 c0560185 e2fd9d88 f8f3e1d8
       f8f3e1dc ebc4e034 f8f3e18c e2fd9ec4 00000000 e2fd9d90 f899c286 c008561c
Call Trace:
 [<f8c0c6ae>] ? chip_command+0x266/0x4b6 [tvaudio]
 [<f8c0c448>] ? chip_command+0x0/0x4b6 [tvaudio]
 [<f899c12a>] ? i2c_cmd+0x0/0x2f [i2c_core]
 [<f899c154>] ? i2c_cmd+0x2a/0x2f [i2c_core]
 [<c0560185>] ? device_for_each_child+0x21/0x49
 [<f899c286>] ? i2c_clients_command+0x1c/0x1e [i2c_core]
 [<f8f283d8>] ? bttv_call_i2c_clients+0x14/0x16 [bttv]
 [<f8f23601>] ? bttv_s_ctrl+0x1bc/0x313 [bttv]
 [<f8f23445>] ? bttv_s_ctrl+0x0/0x313 [bttv]
 [<f8b6096d>] ? __video_do_ioctl+0x1f84/0x3726 [videodev]
 [<c05abb4e>] ? sock_aio_write+0x100/0x10d
 [<c041b23e>] ? kmap_atomic_prot+0x1dd/0x1df
 [<c043a0c9>] ? enqueue_hrtimer+0xc2/0xcd
 [<c04f4fa4>] ? copy_from_user+0x39/0x121
 [<f8b622b9>] ? __video_ioctl2+0x1aa/0x24a [videodev]
 [<c04054fd>] ? do_notify_resume+0x768/0x795
 [<c043c0f7>] ? getnstimeofday+0x34/0xd1
 [<c0437b77>] ? autoremove_wake_function+0x0/0x33
 [<f8b62368>] ? video_ioctl2+0xf/0x13 [videodev]
 [<c048c6f0>] ? vfs_ioctl+0x50/0x69
 [<c048c942>] ? do_vfs_ioctl+0x239/0x24c
 [<c048c995>] ? sys_ioctl+0x40/0x5b
 [<c0405bf2>] ? syscall_call+0x7/0xb
 [<c0620000>] ? cpuid4_cache_sysfs_exit+0x3d/0x69
 =======================
Code:  Bad EIP value.
EIP: [<00000000>] 0x0 SS:ESP 0068:e2fd9d2c

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>