From 6c1c134f4d69883c8ee1732fb787590734fc2caf Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Wed, 18 Nov 2020 10:22:32 +0800
Subject: [PATCH] ati: check x y display parameter values

fix CVE-2020-24352

The source and destination x,y display parameters in ati_2d_blt()
may run off the vga limits if either of s->regs.[src|dst]_[xy] is
zero. Check the parameter values to avoid potential crash.

Reported-by: Gaoning Pan <pgn@zju.edu.cn>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Message-id: 20201021103818.1704030-1-ppandit@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

cherry-pick from commit ca1f9cbfdce4d63b10d57de80fef89a89d92a540
Signed-off-by: Jiajie Li <lijiajie11@huawei.com>
---
 hw/display/ati_2d.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/hw/display/ati_2d.c b/hw/display/ati_2d.c
index 23a8ae0cd8..4dc10ea795 100644
--- a/hw/display/ati_2d.c
+++ b/hw/display/ati_2d.c
@@ -75,8 +75,9 @@ void ati_2d_blt(ATIVGAState *s)
         dst_stride *= bpp;
     }
     uint8_t *end = s->vga.vram_ptr + s->vga.vram_size;
-    if (dst_bits >= end || dst_bits + dst_x + (dst_y + s->regs.dst_height) *
-        dst_stride >= end) {
+    if (dst_x > 0x3fff || dst_y > 0x3fff || dst_bits >= end
+        || dst_bits + dst_x
+         + (dst_y + s->regs.dst_height) * dst_stride >= end) {
         qemu_log_mask(LOG_UNIMP, "blt outside vram not implemented\n");
         return;
     }
@@ -107,8 +108,9 @@ void ati_2d_blt(ATIVGAState *s)
             src_bits += s->regs.crtc_offset & 0x07ffffff;
             src_stride *= bpp;
         }
-        if (src_bits >= end || src_bits + src_x +
-            (src_y + s->regs.dst_height) * src_stride >= end) {
+        if (src_x > 0x3fff || src_y > 0x3fff || src_bits >= end
+            || src_bits + src_x
+             + (src_y + s->regs.dst_height) * src_stride >= end) {
             qemu_log_mask(LOG_UNIMP, "blt outside vram not implemented\n");
             return;
         }
-- 
2.27.0