From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33701) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1euJ91-0000nr-BB for qemu-devel@nongnu.org; Fri, 09 Mar 2018 09:37:20 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1euJ8y-0003HK-6b for qemu-devel@nongnu.org; Fri, 09 Mar 2018 09:37:15 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:58858 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1euJ8y-0003HC-1t for qemu-devel@nongnu.org; Fri, 09 Mar 2018 09:37:12 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 87693406E8A4 for ; Fri, 9 Mar 2018 14:37:07 +0000 (UTC) From: Gerd Hoffmann Date: Fri, 9 Mar 2018 15:37:04 +0100 Message-Id: <20180309143704.13420-1-kraxel@redhat.com> Subject: [Qemu-devel] [PATCH v2] vga: fix region calculation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Gerd Hoffmann Typically the scanline length and the line offset are identical. But in case they are not our calculation for region_end is incorrect. Using line_offset is fine for all scanlines, except the last one where we have to use the actual scanline length. Fixes: CVE-2018-7550 Reported-by: Ross Lagerwall Signed-off-by: Gerd Hoffmann Reviewed-by: Prasad J Pandit Tested-by: Ross Lagerwall --- hw/display/vga.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/hw/display/vga.c b/hw/display/vga.c index 28f298b342..72181330b8 100644 --- a/hw/display/vga.c +++ b/hw/display/vga.c @@ -1483,6 +1483,8 @@ static void vga_draw_graphic(VGACommonState *s, int full_update) region_start = (s->start_addr * 4); region_end = region_start + (ram_addr_t)s->line_offset * height; + region_end += width * s->get_bpp(s) / 8; /* scanline length */ + region_end -= s->line_offset; if (region_end > s->vbe_size) { /* wraps around (can happen with cirrus vbe modes) */ region_start = 0; -- 2.9.3