linux-kernel - Re: [PATCH] Media: video: uvc: integer overflow in uvc_ioctl_ctrl

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Date:	Sun, 11 Dec 2011 11:31:37 +0100
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Mauro Carvalho Chehab <mchehab@...radead.org>
Cc:	Haogang Chen <haogangchen@...il.com>, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Media: video: uvc: integer overflow in uvc_ioctl_ctrl_map()

Hi Mauro,

On Sunday 11 December 2011 11:22:29 Mauro Carvalho Chehab wrote:
> On 29-11-2011 23:22, Laurent Pinchart wrote:
> > Hi Haogang,
> > 
> > On Tuesday 29 November 2011 22:32:25 Haogang Chen wrote:
> >> There is a potential integer overflow in uvc_ioctl_ctrl_map(). When a
> >> large xmap->menu_count is passed from the userspace, the subsequent call
> >> to kmalloc() will allocate a buffer smaller than expected.
> >> map->menu_count and map->menu_info would later be used in a loop (e.g.
> >> in uvc_query_v4l2_ctrl), which leads to out-of-bound access.
> >> 
> >> The patch checks the ioctl argument and returns -EINVAL for zero or too
> >> large values in xmap->menu_count.
> > 
> > Thanks for the patch.
> 
> I'm assuming that either one of you will re-send the patches with the
> pointed changes, so, I'm marking this one with "changes requested" at
> patchwork.

The modified patch is included in my latest pull request.

I had forgotten to CC stable@...nel.org in the commit message. I've updated 
the uvcvideo-next branch, but have you already pulled from it ? If so, could 
you add Cc: stable@...nel.org to the patch, or should I send a v2 for the pull 
request ?

> >> Signed-off-by: Haogang Chen<haogangchen@...il.com>
> >> ---
> >> 
> >>   drivers/media/video/uvc/uvc_v4l2.c |    6 ++++++
> >>   1 files changed, 6 insertions(+), 0 deletions(-)
> >> 
> >> diff --git a/drivers/media/video/uvc/uvc_v4l2.c
> >> b/drivers/media/video/uvc/uvc_v4l2.c index dadf11f..9a180d6 100644
> >> --- a/drivers/media/video/uvc/uvc_v4l2.c
> >> +++ b/drivers/media/video/uvc/uvc_v4l2.c
> >> @@ -58,6 +58,12 @@ static int uvc_ioctl_ctrl_map(struct uvc_video_chain
> >> *chain, break;
> >> 
> >>   	case V4L2_CTRL_TYPE_MENU:
> >> +		if (xmap->menu_count == 0 ||
> >> +		    xmap->menu_count>  INT_MAX / sizeof(*map->menu_info)) {
> > 
> > I'd like to prevent excessive memory consumption by limiting the number
> > of menu entries, similarly to how the driver limits the number of
> > mappings. Defining UVC_MAX_CONTROL_MENU_ENTRIES to 32 in uvcvideo.h
> > should be a reasonable value.
> > 
> >> +			kfree(map);
> >> +			return -EINVAL;
> > 
> > I'd rather do
> > 
> > 	ret = -EINVAL;
> > 	goto done;
> > 
> > to centralize error handling.
> > 
> > If you're fine with both changes I can modify the patch, there's no need
> > to resubmit.
> > 
> >> +		}
> >> +
> >> 
> >>   		size = xmap->menu_count * sizeof(*map->menu_info);
> >>   		map->menu_info = kmalloc(size, GFP_KERNEL);
> >>   		if (map->menu_info == NULL) {

-- 
Regards,

Laurent Pinchart
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