Re: [PATCH] media: uvcvideo: Silence memcpy() run-time false positive warnings

From: Andy Shevchenko <andriy.shevchenko@intel.com>
To: Ricardo Ribalda <ribalda@chromium.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Kees Cook <keescook@chromium.org>,
	ionut_n2001@yahoo.com, Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH] media: uvcvideo: Silence memcpy() run-time false positive warnings
Date: Wed, 8 Feb 2023 00:06:49 +0200	[thread overview]
Message-ID: <Y+LLeYF7CtLjeLbt@smile.fi.intel.com> (raw)
In-Reply-To: <CANiDSCvB8vRp43A1J4BpNZveCvG66XbDmnkKZykbWSFCLX1XUQ@mail.gmail.com>

On Mon, Jan 09, 2023 at 11:46:00AM +0100, Ricardo Ribalda wrote:
> Hi Laurent
> 
> I was thinking about something on the line of the attached patch,
> 
> uvc_frame_header->data could also be replaced with a union.
> 
> Warning, not tested ;)

...

> +struct uvc_frame_header {
> +	u8 length;
> +	u8 flags;
> +	u8 data[];
> +} __packed;

__packed! (See below)

...

> +		pts = (u32 *) header->data;

Ai-ai-ai.
Here is just a yellow flag...

...

>  	uvc_dbg(stream->dev, FRAME,
>  		"%s(): t-sys %lluns, SOF %u, len %u, flags 0x%x, PTS %u, STC %u frame SOF %u\n",
>  		__func__, ktime_to_ns(time), meta->sof, meta->length,
>  		meta->flags,
> +		has_pts ? *pts : 0,

...and here is a red flag. What you need to have is

	void *pts;
	u32 pts_val;

	pts_val = get_unaligned_be32(); // or le32

	...use pts_val...

> +		has_scr ? scr->scr : 0,
> +		has_scr ? scr->frame_sof & 0x7ff : 0);

-- 
With Best Regards,
Andy Shevchenko