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

stable inclusion
from stable-v5.10.173
commit c4d96503d67b2c4de9772521cac84e5f25218c7c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8BFR3

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c4d96503d67b2c4de9772521cac84e5f25218c7c



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[ Upstream commit b8392129 ]

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>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>