Re: [regression 3.4->3.5, bisected] kernel oops when starting capturing from gspca-sn9c20x webcams

[Hans de Goede <hdegoede@redhat.com>]

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Hi,

Thanks for reporting this!

On 07/08/2012 06:25 PM, Frank Schäfer wrote:
> Hi,
>
> running kernel 3.5.rc6 with the two gspca-sn9c20x webcams
>
> 0c45:62b3 Microdia PC Camera with Microphone (SN9C202 + OV9655)
> 0c45:6270 Microdia PC Camera (SN9C201 + MI0360/MT9V011 or
> MI0360SOC/MT9V111) U-CAM PC Camera NE878, Whitcom WHC017, ...
>
> I'm getting the following kernel oops when I start capturing with qv4l2
> (and also Kopete and others):
>
> [   81.719973] gspca_sn9c20x: Set 640x480
> [   81.736805] BUG: unable to handle kernel NULL pointer dereference at
> 0000002c
> [   81.736877] IP: [<f7aebb59>] v4l2_ctrl_g_ctrl+0x9/0x50 [videodev]
> [   81.736901] *pdpt = 000000002c4fa001 *pde = 0000000000000000
> [   81.736922] Oops: 0000 [#1] PREEMPT SMP
> [   81.737055]
> [   81.737071] Pid: 4026, comm: qv4l2 Not tainted 3.4.0-0.1-desktop+ #19
> System manufacturer System Product Name/M2N-VM DH
> [   81.737101] EIP: 0060:[<f7aebb59>] EFLAGS: 00010292 CPU: 1
> [   81.737130] EIP is at v4l2_ctrl_g_ctrl+0x9/0x50 [videodev]
> [   81.737147] EAX: 00000000 EBX: 00000000 ECX: f6c000c0 EDX: 00000001
> [   81.737165] ESI: 00000028 EDI: 00000028 EBP: f5af9c84 ESP: f5af9c7c
> [   81.737183]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> [   81.737200] CR0: 80050033 CR2: 0000002c CR3: 2c941000 CR4: 000007f0
> [   81.737219] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> [   81.737236] DR6: ffff0ff0 DR7: 00000400
> [   81.737252] Process qv4l2 (pid: 4026, ti=f5af8000 task=f594c030
> task.ti=f5af8000)
> [   81.737271] Stack:
> [   81.737290]  00000028 f61c2000 f5af9cd0 f7d1c74c 0000007f 00000000
> f5af9ca4 c0586ba1
> [   81.737318]  ef190444 0000007f 00000080 000001e0 00000280 00000002
> 00000000 02000100
> [   81.737346]  003c2800 00f000a0 f61c2000 00000000 00000000 f5af9d84
> f7b682c0 f71d8bec
> [   81.737366] Call Trace:
> [   81.737390]  [<f7d1c74c>] sd_start+0x2dc/0x450 [gspca_sn9c20x]
> [   81.737421]  [<c0586ba1>] ? usb_alloc_coherent+0x21/0x30
> [   81.737448]  [<f7b682c0>] gspca_init_transfer+0x260/0x420 [gspca_main]
> [   81.737479]  [<c02ea322>] ? __alloc_pages_nodemask+0x142/0x7b0
> [   81.737504]  [<f7b6926b>] vidioc_streamon+0x9b/0xb0 [gspca_main]
> [   81.737535]  [<f7ae4919>] __video_do_ioctl+0x2ba9/0x5780 [videodev]
> [   81.737565]  [<c031b7ee>] ? alloc_pages_current+0x8e/0x100
> [   81.737588]  [<c0230998>] ? kmap_atomic_prot+0xe8/0x110
> [   81.737611]  [<c04824ea>] ? __copy_from_user_ll+0x1a/0x30
> [   81.737630]  [<c0482530>] ? _copy_from_user+0x30/0x50
> [   81.737656]  [<f7ae1b0e>] video_usercopy+0x1de/0x270 [videodev]
> [   81.737679]  [<c0309fc8>] ? mmap_region+0x1e8/0x4b0
> [   81.737706]  [<f7ae1bb2>] video_ioctl2+0x12/0x20 [videodev]
> [   81.737725]  [<f7ae1d70>] ? v4l2_norm_to_name+0x50/0x50 [videodev]
> [   81.737725]  [<f7ae064a>] v4l2_ioctl+0xca/0x190 [videodev]
> [   81.737725]  [<c030a401>] ? do_mmap_pgoff+0x171/0x2e0
> [   81.737725]  [<f7ae0580>] ? v4l2_open+0x120/0x120 [videodev]
> [   81.737725]  [<c0344074>] do_vfs_ioctl+0x74/0x2e0
> [   81.737725]  [<c0344347>] sys_ioctl+0x67/0x80
> [   81.737725]  [<c07242dd>] syscall_call+0x7/0xb
> [   81.737725] Code: 55 f0 89 02 8b 46 10 8b 40 14 e8 03 61 c3 c8 89 f8
> 83 c4 04 5b 5e 5f 5d c3 89 f6 8d bc 27 00 00 00 00 55 89 e5 53 89 c3 83
> ec 04 <8b> 40 2c c7 45 f8 00 00 00 00 8d 50 fb 83 fa 02 77 09 80 b8 d3
> [   81.737725] EIP: [<f7aebb59>] v4l2_ctrl_g_ctrl+0x9/0x50 [videodev]
> SS:ESP 0068:f5af9c7c
> [   81.737725] CR2: 000000000000002c
> [   81.743027] ---[ end trace 1c291740d69b151f ]---
>
>
> This is a regression from kernel 3.4.x.
> The causing commit seems to be
>
>
> commit 63069da1c8ef0abcdb74b0ea1c461d23fb9181d9
> Author: Hans Verkuil <hans.verkuil@cisco.com>
> Date:   Sun May 6 09:28:29 2012 -0300
>
>      [media] gcpca_sn9c20x: Convert to the control framework
>
>      HdG: Small fix: don't register some controls for sensors which don't
>      have an implementation for them.
>
>      Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
>      Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>      Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
>
>
> Should I open a bug report at bugzilla, too ?

That won't be necessary, the attached patch should fix this, can you
give it a try please?

Thanks,

Hans

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>From e3d5933cf00270768b202041adf463ffc4fc9544 Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdegoede@redhat.com>
Date: Sun, 8 Jul 2012 19:41:14 +0200
Subject: [PATCH] gspca_sn9c20x: Fix NULL pointer dereference
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Don't call v4l2_ctrl_g_ctrl on ctrls which the model cam in question
does not have.

Reported-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/media/video/gspca/sn9c20x.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/media/video/gspca/sn9c20x.c b/drivers/media/video/gspca/sn9c20x.c
index 6c31e46..b9c6f17 100644
--- a/drivers/media/video/gspca/sn9c20x.c
+++ b/drivers/media/video/gspca/sn9c20x.c
@@ -2070,10 +2070,13 @@ static int sd_start(struct gspca_dev *gspca_dev)
 	set_gamma(gspca_dev, v4l2_ctrl_g_ctrl(sd->gamma));
 	set_redblue(gspca_dev, v4l2_ctrl_g_ctrl(sd->blue),
 			v4l2_ctrl_g_ctrl(sd->red));
-	set_gain(gspca_dev, v4l2_ctrl_g_ctrl(sd->gain));
-	set_exposure(gspca_dev, v4l2_ctrl_g_ctrl(sd->exposure));
-	set_hvflip(gspca_dev, v4l2_ctrl_g_ctrl(sd->hflip),
-			v4l2_ctrl_g_ctrl(sd->vflip));
+	if (sd->gain)
+		set_gain(gspca_dev, v4l2_ctrl_g_ctrl(sd->gain));
+	if (sd->exposure)
+		set_exposure(gspca_dev, v4l2_ctrl_g_ctrl(sd->exposure));
+	if (sd->hflip)
+		set_hvflip(gspca_dev, v4l2_ctrl_g_ctrl(sd->hflip),
+				v4l2_ctrl_g_ctrl(sd->vflip));
 
 	reg_w1(gspca_dev, 0x1007, 0x20);
 	reg_w1(gspca_dev, 0x1061, 0x03);
@@ -2176,7 +2179,7 @@ static void sd_dqcallback(struct gspca_dev *gspca_dev)
 	struct sd *sd = (struct sd *) gspca_dev;
 	int avg_lum;
 
-	if (!v4l2_ctrl_g_ctrl(sd->autogain))
+	if (sd->autogain == NULL || !v4l2_ctrl_g_ctrl(sd->autogain))
 		return;
 
 	avg_lum = atomic_read(&sd->avg_lum);
-- 
1.7.10.4