From 8f63265efeb6f92e63f7e749cb26131b68b20df7 Mon Sep 17 00:00:00 2001
From: Li Qiang <liqiang6-s@360.cn>
Date: Mon, 13 Feb 2017 15:22:15 +0000
Subject: [PATCH] cirrus: fix oob access issue (CVE-2017-2615)

When doing bitblt copy in backward mode, we should minus the
blt width first just like the adding in the forward mode. This
can avoid the oob access of the front of vga's vram.

This is XSA-208.

upstream-commit-id: 62d4c6bd5263bb8413a06c80144fc678df6dfb64

Signed-off-by: Li Qiang <liqiang6-s@360.cn>

{ kraxel: with backward blits (negative pitch) addr is the topmost
          address, so check it as-is against vram size ]

[ This is CVE-2017-2615 / XSA-208  - Ian Jackson ]

Cc: qemu-stable@nongnu.org
Cc: P J P <ppandit@redhat.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Wolfgang Bumiller <w.bumiller@proxmox.com>
Fixes: d3532a0db02296e687711b8cdc7791924efccea0 (CVE-2014-8106)
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 1485938101-26602-1-git-send-email-kraxel@redhat.com
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
---
 hw/cirrus_vga.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/hw/cirrus_vga.c b/hw/cirrus_vga.c
index e6c3893..364e22d 100644
--- a/hw/cirrus_vga.c
+++ b/hw/cirrus_vga.c
@@ -308,10 +308,9 @@ static bool blit_region_is_unsafe(struct CirrusVGAState *s,
     }
     if (pitch < 0) {
         int64_t min = addr
-            + ((int64_t)s->cirrus_blt_height-1) * pitch;
-        int32_t max = addr
-            + s->cirrus_blt_width;
-        if (min < 0 || max >= s->vram_size) {
+            + ((int64_t)s->cirrus_blt_height - 1) * pitch
+            - s->cirrus_blt_width;
+        if (min < -1 || addr >= s->vram_size) {
             return true;
         }
     } else {
-- 
2.1.4