drm/vmwgfx: Validate the box size for the snooped cursor

commit 4cf949c7 upstream.

Invalid userspace dma surface copies could potentially overflow
the memcpy from the surface to the snooped image leading to crashes.
To fix it the dimensions of the copybox have to be validated
against the expected size of the snooped cursor.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Fixes: 2ac86371 ("vmwgfx: Snoop DMA transfers with non-covering sizes")
Cc: <stable@vger.kernel.org> # v3.2+
Reviewed-by: Michael Banack <banackm@vmware.com>
Reviewed-by: Martin Krastev <krastevm@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221026031936.1004280-1-zack@kde.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>