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From 3ed3904f7411bd5896aebdfcc6fe202dbfc2eef6 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Mon, 9 Apr 2018 13:27:36 +0200
Subject: [PATCH 2/2] vga: fix region calculation

RH-Author: Gerd Hoffmann <kraxel@redhat.com>
Message-id: <20180409132736.24598-3-kraxel@redhat.com>
Patchwork-id: 79512
O-Subject: [RHEL-7.5 qemu-kvm PATCH 2/2] vga: fix region calculation
Bugzilla: 1567913
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: John Snow <jsnow@redhat.com>

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 <ross.lagerwall@citrix.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Prasad J Pandit <pjp@fedoraproject.org>
Tested-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Message-id: 20180309143704.13420-1-kraxel@redhat.com
(cherry picked from commit 7cdc61becd095b64a786b2625f321624e7111f3d)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/display/vga.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/display/vga.c b/hw/display/vga.c
index 8e6c6d6..9270a75 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1535,6 +1535,8 @@ 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;
-- 
1.8.3.1