Date:	Mon, 17 Mar 2008 23:51:56 +0200
From:	Bongani Hlope <bonganilinux@...b.co.za>
To:	Robert Fitzsimons <robfitz@...k.net>
Cc:	Mauro Carvalho Chehab <mchehab@...radead.org>,
	video4linux-list@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: 2.6.25-rc[12] Video4Linux Bttv Regression

On Wednesday 27 February 2008 03:42:38 Robert Fitzsimons wrote:
> > I think I might have seen this problem but it didn't cause a oops for
> > me,
>
> Ok, I found the cause of the oops.  Some of radio tuner code was
> expecting a struct bttv_fh to be allocated but this wasn't done in
> radio_open.  So it would dereference an invalid data structure, causing
> a hang for me and an oops for Bongani.  I also had to add support for
> the radio tuner to some shared functions.  Patches to follow.
>
> Robert

More info... 

The Oops seems to be caused by a size mismatch that causes memset to write 
over other variables in the stack... The following debug hack moved oops to 
another point in the v4l1-compact code..

So memset(&tun2,0,sizeof(tun2))  seems to be overwriting btv->lock->wait_list:

--- drivers/media/video/v4l1-compat.c~  2007-11-13 10:25:52.000000000 +0200
+++ drivers/media/video/v4l1-compat.c   2008-03-17 23:17:38.000000000 +0200
@@ -688,7 +688,7 @@
        {
                struct video_tuner      *tun = arg;

-               memset(&tun2,0,sizeof(tun2));
+               memset(&tun2,-1,sizeof(tun2));
                err = drv(inode, file, VIDIOC_G_TUNER, &tun2);
                if (err < 0) {
                        dprintk("VIDIOCGTUNER / VIDIOC_G_TUNER: %d\n",err);

The new oops, where there's another memset(&tun2,0,sizeof(tun2)):

BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
IP: [<ffffffff8045a329>] __mutex_lock_slowpath+0x3b/0xb2
PGD 699d9067 PUD 65837067 PMD 0
Oops: 0002 [1] PREEMPT SMP
CPU 1
Modules linked in: snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq 
binfmt_misc loop nls_cp437 vfat fat nls_iso8859_1 ntfs thermal processor fan 
container button pcspkr snd_pcm_oss snd_mixer_oss snd_emu10k1 tuner tea5767 
tda8290 tuner_xc2028 tda9887 tuner_simple snd_rawmidi mt20xx snd_ac97_codec 
tea5761 bttv ac97_bus snd_pcm ir_common firewire_ohci snd_seq_device 
compat_ioctl32 firewire_core snd_timer uhci_hcd videodev ehci_hcd 
snd_page_alloc v4l1_compat crc_itu_t snd_util_mem usbcore v4l2_common 
snd_hwdep videobuf_dma_sg ohci1394 ide_cd_mod snd videobuf_core emu10k1_gp 
ieee1394 sr_mod btcx_risc evdev gameport i2c_viapro tveeprom cdrom sg tg3 
soundcore
Pid: 4230, comm: radio Not tainted 2.6.25-rc5-dirty #46
RIP: 0010:[<ffffffff8045a329>]  [<ffffffff8045a329>] 
__mutex_lock_slowpath+0x3b/0xb2
RSP: 0018:ffff8100658455e8  EFLAGS: 00010246
RAX: ffff81007fbeff10 RBX: ffff81007fbeff08 RCX: 0000000000000000
RDX: ffff8100658455e8 RSI: ffffffff8816711c RDI: ffff81007fbeff0c
RBP: ffff810065845628 R08: ffffffff880e98df R09: 0000000000000002
R10: ffff810065845f38 R11: 0000000000000246 R12: ffff81007fbeff0c
R13: 0000000000000000 R14: ffff8100699d0d10 R15: ffffffff88167110
FS:  00007f0c740e46f0(0000) GS:ffff81007fb6adc0(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000065835000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process radio (pid: 4230, threadinfo ffff810065844000, task ffff8100699d0d10)
Stack:  ffff81007fbeff10 ffff810065845774 0000000265845688 ffff810065845768
 ffff81007fbef800 ffff810065845c68 0000000000000000 ffff81007fbeff08
 ffff810065845638 ffffffff8045a16f ffff810065845668 ffffffff8814692f
Call Trace:
 [<ffffffff8045a16f>] mutex_lock+0xe/0x10
 [<ffffffff8814692f>] :bttv:bttv_s_frequency+0x46/0x9f
 [<ffffffff880ec583>] :videodev:__video_do_ioctl+0x2ca4/0x2e16
 [<ffffffff8022b6fe>] ? hrtick_set+0xdf/0xe8
 [<ffffffff8020a003>] ? default_idle+0x0/0x5f
 [<ffffffff80459c51>] ? thread_return+0x6c/0xbf
 [<ffffffff880d52a9>] :v4l1_compat:v4l_compat_translate_ioctl+0x1116/0x1b01
 [<ffffffff802ff5bb>] ? generic_unplug_device+0x2c/0x30
 [<ffffffff880e98df>] ? :videodev:__video_do_ioctl+0x0/0x2e16
 [<ffffffff80266946>] ? mark_page_accessed+0x20/0x36
 [<ffffffff802a57af>] ? __find_get_block+0x153/0x165
 [<ffffffff802a57e1>] ? __getblk+0x20/0x22b
 [<ffffffff803021ff>] ? blk_recount_segments+0x3e/0x68
 [<ffffffff80260795>] ? mempool_alloc+0x48/0xf9
 [<ffffffff8028073b>] ? cache_alloc_refill+0x1cc/0x233
 [<ffffffff80302a5a>] ? blk_rq_map_sg+0x12b/0x24b
 [<ffffffff80238971>] ? lock_timer_base+0x26/0x4a
 [<ffffffff8038df34>] ? dma_timer_expiry+0x0/0x6d
 [<ffffffff80238b1c>] ? __mod_timer+0xc4/0xd6
 [<ffffffff80311a3b>] ? __delay+0x27/0x59
 [<ffffffff80311a3b>] ? __delay+0x27/0x59
 [<ffffffff80311a3b>] ? __delay+0x27/0x59
 [<ffffffff80311a3b>] ? __delay+0x27/0x59
 [<ffffffff80311a3b>] ? __delay+0x27/0x59
 [<ffffffff80311aef>] ? __udelay+0x40/0x42
 [<ffffffff803c1ba4>] ? i2c_stop+0x47/0x4b
 [<ffffffff803c236b>] ? bit_xfer+0x412/0x423
 [<ffffffff803c01ed>] ? i2c_transfer+0x79/0x85
 [<ffffffff881a3318>] ? :tuner_simple:simple_set_params+0x2b9/0xc18
 [<ffffffff8022589b>] ? enqueue_task_fair+0x179/0x186
 [<ffffffff80227ff2>] ? task_rq_lock+0x3d/0x73
 [<ffffffff802284b9>] ? try_to_wake_up+0x1ae/0x1bf
 [<ffffffff8021a49d>] ? smp_send_reschedule+0x1d/0x1f
 [<ffffffff802284d7>] ? default_wake_function+0xd/0xf
 [<ffffffff802246cc>] ? __wake_up_common+0x46/0x75
 [<ffffffff880e9a18>] :videodev:__video_do_ioctl+0x139/0x2e16
 [<ffffffff80357b8c>] ? n_tty_receive_buf+0xf18/0xf77
 [<ffffffff80260449>] ? filemap_fault+0x1fe/0x371
 [<ffffffff880eca95>] :videodev:video_ioctl2+0x1b8/0x259
 [<ffffffff802426de>] ? remove_wait_queue+0x3c/0x41
 [<ffffffff80226ea2>] ? __wake_up+0x43/0x4f
 [<ffffffff80291252>] vfs_ioctl+0x5e/0x77
 [<ffffffff802914b8>] do_vfs_ioctl+0x24d/0x262
 [<ffffffff8029150f>] sys_ioctl+0x42/0x67
 [<ffffffff802862af>] ? sys_write+0x47/0x70
 [<ffffffff8020b32b>] system_call_after_swapgs+0x7b/0x80


Code: 89 fb 4c 89 e7 48 83 ec 20 65 4c 8b 34 25 00 00 00 00 e8 e5 0f 00 00 48 
8d 43 08 48 8d 55 c0 48 8b 48 08 48 89 45 c0 48 89 50 08 <48> 89 11 48 83 ca 
ff 48 89 4d c8 4c 89 75 d0 48 89 d0 87 03 ff
RIP  [<ffffffff8045a329>] __mutex_lock_slowpath+0x3b/0xb2
 RSP <ffff8100658455e8>
CR2: 0000000000000000
---[ end trace 821f8e64b81db17b ]---




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