From: Ricardo Ribalda <ribalda@chromium.org>
To: Kees Cook <keescook@chromium.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
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: Fri, 6 Jan 2023 12:43:44 +0100 [thread overview]
Message-ID: <CANiDSCtTz4mpTz4RHBzNXL=yBvXNXHBZQ-HYMFegLytoScW4eA@mail.gmail.com> (raw)
In-Reply-To: <20230106061659.never.817-kees@kernel.org>
Hi Kees
Thanks for the patch
Would it make more sense to replace *mem with a structure/union. Something like:
https://patchwork.linuxtv.org/project/linux-media/patch/20221214-uvc-status-alloc-v4-0-f8e3e2994ebd@chromium.org/
Regards!
On Fri, 6 Jan 2023 at 07:19, Kees Cook <keescook@chromium.org> wrote:
>
> The memcpy() in uvc_video_decode_meta() intentionally copies across the
> length and flags members and into the trailing buf flexible array.
> Split the copy so that the compiler can better reason about (the lack
> of) buffer overflows here. Avoid the run-time false positive warning:
>
> memcpy: detected field-spanning write (size 12) of single field "&meta->length" at drivers/media/usb/uvc/uvc_video.c:1355 (size 1)
>
> Additionally fix a typo in the documentation for struct uvc_meta_buf.
>
> Reported-by: ionut_n2001@yahoo.com
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216810
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: linux-media@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> drivers/media/usb/uvc/uvc_video.c | 4 +++-
> include/uapi/linux/uvcvideo.h | 2 +-
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index d2eb9066e4dc..b67347ab4181 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -1352,7 +1352,9 @@ static void uvc_video_decode_meta(struct uvc_streaming *stream,
> if (has_scr)
> memcpy(stream->clock.last_scr, scr, 6);
>
> - memcpy(&meta->length, mem, length);
> + meta->length = mem[0];
> + meta->flags = mem[1];
> + memcpy(meta->buf, &mem[2], length - 2);
> meta_buf->bytesused += length + sizeof(meta->ns) + sizeof(meta->sof);
>
> uvc_dbg(stream->dev, FRAME,
> diff --git a/include/uapi/linux/uvcvideo.h b/include/uapi/linux/uvcvideo.h
> index 8288137387c0..a9d0a64007ba 100644
> --- a/include/uapi/linux/uvcvideo.h
> +++ b/include/uapi/linux/uvcvideo.h
> @@ -86,7 +86,7 @@ struct uvc_xu_control_query {
> * struct. The first two fields are added by the driver, they can be used for
> * clock synchronisation. The rest is an exact copy of a UVC payload header.
> * Only complete objects with complete buffers are included. Therefore it's
> - * always sizeof(meta->ts) + sizeof(meta->sof) + meta->length bytes large.
> + * always sizeof(meta->ns) + sizeof(meta->sof) + meta->length bytes large.
> */
> struct uvc_meta_buf {
> __u64 ns;
> --
> 2.34.1
>
--
Ricardo Ribalda
next prev parent reply other threads:[~2023-01-06 11:44 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-06 6:17 [PATCH] media: uvcvideo: Silence memcpy() run-time false positive warnings Kees Cook
2023-01-06 11:43 ` Ricardo Ribalda [this message]
2023-01-06 20:19 ` Kees Cook
2023-01-07 1:42 ` Laurent Pinchart
2023-01-09 10:46 ` Ricardo Ribalda
2023-02-07 22:06 ` Andy Shevchenko
2023-02-22 13:14 ` Ricardo Ribalda
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