File 0162-cirrus_vga-fix-off-by-one-in-blit_r.patch of Package qemu.9343

Overview Repositories Revisions Requests Users Attributes Meta

File 0162-cirrus_vga-fix-off-by-one-in-blit_r.patch of Package qemu.9343

From 57b4eadd5e85b44c18471f1cce901146c7065f9c Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 10 Feb 2016 17:17:39 +0100
Subject: [PATCH] cirrus_vga: fix off-by-one in blit_region_is_unsafe

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: Bruce Rogers <brogers@suse.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 f4989a024f..bc82bb8dc7 100644
--- a/hw/display/cirrus_vga.c
+++ b/hw/display/cirrus_vga.c
@@ -274,14 +274,14 @@ 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;
         }
     }

Places

File 0162-cirrus_vga-fix-off-by-one-in-blit_r.patch of Package qemu.9343

Places