Hi,

Thanks for the patch I've added this to my "gspca" tree, and this
will be included in my next pull-request to Mauro for 3.12

Regards,

Hans



On 08/15/2013 12:29 PM, Antonio Ospite wrote:
sd_start() operates on device controls but after the conversion to the
v4l2 control framework in commits 62bba5d and 1bd7d6a controls are
initialized in sd_init_controls() which is called _after_ sd_init():

The change fixes a NULL pointer dereference for Hercules Blog Webcam;
the problem is observable since 3.6:

   gspca_main: v2.14.0 registered
   gspca_main: ov534-2.14.0 probing 06f8:3002
   BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
   IP: [<ffffffffa03c1b01>] v4l2_ctrl_g_ctrl+0x11/0x60 [videodev]
   PGD 0
   Oops: 0000 [#1] SMP
   Modules linked in: gspca_ov534(+) gspca_main videodev rfcomm bnep ppdev 
bluetooth binfmt_misc snd_hda_codec_hdmi snd_hda_codec_realtek stir4200 irda 
crc_ccitt usblp snd_hda_intel snd_hda_codec snd_hwdep snd_pcm hid_generic 
snd_page_alloc snd_seq_midi snd_seq_midi_event usbhid snd_rawmidi snd_seq 
snd_seq_device snd_timer hid i915 snd psmouse drm_kms_helper serio_raw mei_me 
drm mei soundcore video i2c_algo_bit lpc_ich mac_hid coretemp lp parport 
firewire_ohci firewire_core crc_itu_t ahci libahci alx mdio r8169 mii [last 
unloaded: parport_pc]
   CPU: 3 PID: 4352 Comm: modprobe Not tainted 3.11.0-031100rc2-generic 
#201307211535
   Hardware name: Gigabyte Technology Co., Ltd. To be filled by 
O.E.M./Z77-DS3H, BIOS F9 09/19/2012
   task: ffff8801c20f9770 ti: ffff8801ceaa0000 task.ti: ffff8801ceaa0000
   RIP: 0010:[<ffffffffa03c1b01>]  [<ffffffffa03c1b01>] 
v4l2_ctrl_g_ctrl+0x11/0x60 [videodev]
   RSP: 0018:ffff8801ceaa1af8  EFLAGS: 00010292
   RAX: 0000000000000001 RBX: 0000000000000000 RCX: 000000000001988b
   RDX: 000000000001988a RSI: ffffffffa032745a RDI: 0000000000000000
   RBP: ffff8801ceaa1b28 R08: 0000000000017380 R09: ffffea0008419d80
   R10: ffffffff81538f5a R11: 0000000000000002 R12: ffffffffa03273dc
   R13: ffffffffa03273dc R14: 0000000000000000 R15: ffffffffa03270a0
   FS:  00007f72d564a740(0000) GS:ffff88021f380000(0000) knlGS:0000000000000000
   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
   CR2: 0000000000000050 CR3: 00000001bd1f0000 CR4: 00000000001407e0
   Stack:
    ffff8801ceaa1b28 ffffffffa0325cff ffff8801000001f4 ffff8801ceb44000
    ffffffffa03273dc ffff8801ceb44000 ffff8801ceaa1b58 ffffffffa032688e
    ffff8801ceb44000 ffffffffa03274f0 ffffffffa03274f0 ffff8801ceb44380
   Call Trace:
    [<ffffffffa0325cff>] ? sccb_w_array+0x3f/0x80 [gspca_ov534]
    [<ffffffffa032688e>] sd_start+0xce/0x2b0 [gspca_ov534]
    [<ffffffffa0326bf9>] sd_init+0x189/0x1e8 [gspca_ov534]
    [<ffffffffa02a0c95>] gspca_dev_probe2+0x285/0x410 [gspca_main]
    [<ffffffffa02a0e58>] gspca_dev_probe+0x38/0x60 [gspca_main]
    [<ffffffffa0325081>] sd_probe+0x21/0x30 [gspca_ov534]
    [<ffffffff8153c960>] usb_probe_interface+0x1c0/0x2f0
    [<ffffffff8148758c>] really_probe+0x6c/0x330
    [<ffffffff814879d7>] driver_probe_device+0x47/0xa0
    [<ffffffff81487adb>] __driver_attach+0xab/0xb0
    [<ffffffff81487a30>] ? driver_probe_device+0xa0/0xa0
    [<ffffffff814857be>] bus_for_each_dev+0x5e/0x90
    [<ffffffff8148714e>] driver_attach+0x1e/0x20
    [<ffffffff81486bdc>] bus_add_driver+0x10c/0x290
    [<ffffffff8148805d>] driver_register+0x7d/0x160
    [<ffffffff8153b590>] usb_register_driver+0xa0/0x160
    [<ffffffffa0067000>] ? 0xffffffffa0066fff
    [<ffffffffa006701e>] sd_driver_init+0x1e/0x1000 [gspca_ov534]
    [<ffffffff8100212a>] do_one_initcall+0xfa/0x1b0
    [<ffffffff810578c3>] ? set_memory_nx+0x43/0x50
    [<ffffffff81712e8d>] do_init_module+0x80/0x1d1
    [<ffffffff810d2079>] load_module+0x4c9/0x5f0
    [<ffffffff810cf7b0>] ? add_kallsyms+0x210/0x210
    [<ffffffff810d2254>] SyS_init_module+0xb4/0x100
    [<ffffffff817333ef>] tracesys+0xe1/0xe6
   Code: a0 09 00 00 48 c7 c7 30 c3 3c a0 e8 7a 38 ca e0 eb cf 0f 1f 84 00 00 00 00 
00 0f 1f 44 00 00 55 48 89 e5 53 48 89 fb 48 83 ec 28 <8b> 47 50 83 e8 05 83 f8 
02 77 09 80 b8 20 8c 3c a0 00 74 1d 48
   RIP  [<ffffffffa03c1b01>] v4l2_ctrl_g_ctrl+0x11/0x60 [videodev]
    RSP <ffff8801ceaa1af8>
   CR2: 0000000000000050
   ---[ end trace 6786f15abfd2ac90 ]---

Original bug report from:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1173723/

Signed-off-by: Antonio Ospite <osp...@studenti.unina.it>
Tested-by: Yaroslav Zakharuk <slav...@gmail.com>
Cc: <sta...@vger.kernel.org> # 3.6+
---
  drivers/media/usb/gspca/ov534.c | 3 +--
  1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/media/usb/gspca/ov534.c b/drivers/media/usb/gspca/ov534.c
index 2e28c81..03a33c4 100644
--- a/drivers/media/usb/gspca/ov534.c
+++ b/drivers/media/usb/gspca/ov534.c
@@ -1305,8 +1305,7 @@ static int sd_init(struct gspca_dev *gspca_dev)
        ov534_set_led(gspca_dev, 1);
        sccb_w_array(gspca_dev, sensor_init[sd->sensor].val,
                        sensor_init[sd->sensor].len);
-       if (sd->sensor == SENSOR_OV767x)
-               sd_start(gspca_dev);
+
        sd_stopN(gspca_dev);
  /*    set_frame_rate(gspca_dev);      */


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