From 6420a8c59712cce74ad689c0d692982665a785b0 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Fri, 20 Oct 2017 11:06:19 +0200
Subject: [PATCH 4/7] cirrus: fix oob access in mode4and5 write functions

RH-Author: Gerd Hoffmann <kraxel@redhat.com>
Message-id: <20171020110619.2541-12-kraxel@redhat.com>
Patchwork-id: 77403
O-Subject: [RHEL-7.5 qemu-kvm PATCH 11/11] cirrus: fix oob access in mode4and5 write functions
Bugzilla: 1501295
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

Move dst calculation into the loop, so we apply the mask on each
interation and will not overflow vga memory.

Cc: Prasad J Pandit <pjp@fedoraproject.org>
Reported-by: Niu Guoxiang <niuguoxiang@huawei.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20171011084314.21752-1-kraxel@redhat.com
(cherry picked from commit eb38e1bc3740725ca29a535351de94107ec58d51)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/display/cirrus_vga.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
index c1324ab..a07fa9c 100644
--- a/hw/display/cirrus_vga.c
+++ b/hw/display/cirrus_vga.c
@@ -2023,15 +2023,14 @@ static void cirrus_mem_writeb_mode4and5_8bpp(CirrusVGAState * s,
     unsigned val = mem_value;
     uint8_t *dst;
 
-    dst = s->vga.vram_ptr + (offset &= s->cirrus_addr_mask);
     for (x = 0; x < 8; x++) {
+        dst = s->vga.vram_ptr + ((offset + x) & s->cirrus_addr_mask);
 	if (val & 0x80) {
 	    *dst = s->cirrus_shadow_gr1;
 	} else if (mode == 5) {
 	    *dst = s->cirrus_shadow_gr0;
 	}
 	val <<= 1;
-	dst++;
     }
     memory_region_set_dirty(&s->vga.vram, offset, 8);
 }
@@ -2045,8 +2044,8 @@ static void cirrus_mem_writeb_mode4and5_16bpp(CirrusVGAState * s,
     unsigned val = mem_value;
     uint8_t *dst;
 
-    dst = s->vga.vram_ptr + (offset &= s->cirrus_addr_mask);
     for (x = 0; x < 8; x++) {
+        dst = s->vga.vram_ptr + ((offset + 2 * x) & s->cirrus_addr_mask & ~1);
 	if (val & 0x80) {
 	    *dst = s->cirrus_shadow_gr1;
 	    *(dst + 1) = s->vga.gr[0x11];
@@ -2055,7 +2054,6 @@ static void cirrus_mem_writeb_mode4and5_16bpp(CirrusVGAState * s,
 	    *(dst + 1) = s->vga.gr[0x10];
 	}
 	val <<= 1;
-	dst += 2;
     }
     memory_region_set_dirty(&s->vga.vram, offset, 16);
 }
-- 
1.8.3.1