From 8d230a5a57512c84545bd6345775e69b4b3b1983 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 7 Feb 2017 10:07:46 +0100
Subject: [PATCH 03/11] cirrus_vga: fix off-by-one in blit_region_is_unsafe

RH-Author: Gerd Hoffmann <kraxel@redhat.com>
Message-id: <1486462072-32174-2-git-send-email-kraxel@redhat.com>
Patchwork-id: 73564
O-Subject: [RHEL-7.4 qemu-kvm PATCH 1/7] cirrus_vga: fix off-by-one in blit_region_is_unsafe
Bugzilla: 1418233
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

From: Paolo Bonzini <pbonzini@redhat.com>

The "max" value is being compared with >=, but addr + width points to
the first byte that will _not_ be copied.  Laszlo suggested using a
"greater than" comparison, instead of subtracting one like it is
already done above for the height, so that max remains always positive.

The mistake is "safe"---it will reject some blits, but will never cause
out-of-bounds writes.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1455121059-18280-1-git-send-email-pbonzini@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit d2ba7ecb348d3b996fcd920cf1ca7b72722c1dfd)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/display/cirrus_vga.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
index 717ecdb..c42dfcf 100644
--- a/hw/display/cirrus_vga.c
+++ b/hw/display/cirrus_vga.c
@@ -272,14 +272,14 @@ static bool blit_region_is_unsafe(struct CirrusVGAState *s,
             + ((int64_t)s->cirrus_blt_height-1) * pitch;
         int32_t max = addr
             + s->cirrus_blt_width;
-        if (min < 0 || max >= s->vga.vram_size) {
+        if (min < 0 || max > s->vga.vram_size) {
             return true;
         }
     } else {
         int64_t max = addr
             + ((int64_t)s->cirrus_blt_height-1) * pitch
             + s->cirrus_blt_width;
-        if (max >= s->vga.vram_size) {
+        if (max > s->vga.vram_size) {
             return true;
         }
     }
-- 
1.8.3.1