linux-kernel - Buffer overflow in uvc-video.

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Date:	Sat, 20 Sep 2008 20:12:58 +1200
From:	Ralph Loader <suckfish@...g.co.nz>
To:	linux-uvc-devel <linux-uvc-devel@...ts.berlios.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Buffer overflow in uvc-video.

Hi,

There appears to be a buffer overflow in
drivers/media/video/uvc/uvc_ctrl.c:

Sep 20 17:53:12 i kernel: BUG kmalloc-8 (Not tainted): Redzone
overwritten Sep 20 17:53:12 i kernel:
--------------------------------------------------------------------
--------- Sep 20 17:53:12 i kernel:
Sep 20 17:53:12 i kernel: INFO: 0xf2c5ce08-0xf2c5ce0b. First byte 0xa1
instead of 0xcc 
Sep 20 17:53:12 i kernel: INFO: Allocated in
uvc_query_v4l2_ctrl+0x3c/0x239 [uvcvideo] age=13 cpu=1 pid=4975
...


A fixed size 8-byte buffer is allocated, and a variable size field is
read into it; there is no particular bound on the size of the field
(it is dependent on hardware and configuration) and it can overflow
[also verified by inserting printk's.]

The patch below attempts to size the buffer to the correctly; I do not
know if sufficient validation of that size is carried out.

Cheers,
Ralph Loader.

diff --git a/drivers/media/video/uvc/uvc_ctrl.c
b/drivers/media/video/uvc/uvc_ct rl.c
index 6ef3e52..feab12a 100644
--- a/drivers/media/video/uvc/uvc_ctrl.c
+++ b/drivers/media/video/uvc/uvc_ctrl.c
@@ -592,7 +592,7 @@ int uvc_query_v4l2_ctrl(struct uvc_video_device
*video, if (ctrl == NULL)
                return -EINVAL;
 
-       data = kmalloc(8, GFP_KERNEL);
+       data = kmalloc(ctrl->info->size, GFP_KERNEL);
        if (data == NULL)
                return -ENOMEM;
 
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