video: uvesafb: Fix integer overflow in allocation

BugLink: https://bugs.launchpad.net/bugs/1784382

commit 9f645bcc upstream.

cmap->len can get close to INT_MAX/2, allowing for an integer overflow in
allocation. This uses kmalloc_array() instead to catch the condition.
Reported-by: Dr Silvio Cesare of InfoSect <silvio.cesare@gmail.com>
Fixes: 8bdb3a2d ("uvesafb: the driver core")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/video/fbdev/uvesafb.c

@@ -1059,7 +1059,8 @@ static int uvesafb_setcmap(struct fb_cmap *cmap, struct fb_info *info)
 		    info->cmap.len || cmap->start < info->cmap.start)
 			return -EINVAL;
 
-		entries = kmalloc(sizeof(*entries) * cmap->len, GFP_KERNEL);
+		entries = kmalloc_array(cmap->len, sizeof(*entries),
+					GFP_KERNEL);
 		if (!entries)
 			return -ENOMEM;