media: uvcvideo: Silence memcpy() run-time false positive warnings

[ Upstream commit b839212988575c701aab4d3d9ca15e44c87e383c ]

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
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 698aecf1aad487de41e9c066ba3148b62daa33f7..e676a9ef6f0d6938611431368adf7c9b004929a5 100644 (file)
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1308,7 +1308,9 @@ 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_trace(UVC_TRACE_FRAME,

diff --git a/include/uapi/linux/uvcvideo.h b/include/uapi/linux/uvcvideo.h
index f80f05b3c423f3b2a5b0372ab03ba41f3e173348..2140923661934d4ef7ffffd25a15eae92d1aca37 100644 (file)
--- 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;