From 1ebe0e71d04bfdc76777a3a672e873f006d207e2 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Fri, 5 Feb 2021 10:38:24 +0800
Subject: [PATCH] ati: use vga_read_byte in ati_cursor_define
MIME-Version: 1.0
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fix CVE-2019-20808

This makes sure reads are confined to vga video memory.

v3: use uint32_t, fix cut+paste bug.
v2: fix ati_cursor_draw_line too.

Reported-by: xu hang <flier_m@outlook.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190917111441.27405-3-kraxel@redhat.com

cherry-pick from aab0e2a661b2b6bf7915c0aefe807fb60d6d9d13
Signed-off-by: Jiajie Li <lijiajie11@huawei.com>
---
 hw/display/ati.c         | 21 ++++++++---------
 hw/display/vga-access.h  | 49 ++++++++++++++++++++++++++++++++++++++++
 hw/display/vga-helpers.h | 27 +---------------------
 3 files changed, 60 insertions(+), 37 deletions(-)
 create mode 100644 hw/display/vga-access.h

diff --git a/hw/display/ati.c b/hw/display/ati.c
index 5943040416..b17569874e 100644
--- a/hw/display/ati.c
+++ b/hw/display/ati.c
@@ -19,6 +19,7 @@
 #include "qemu/osdep.h"
 #include "ati_int.h"
 #include "ati_regs.h"
+#include "vga-access.h"
 #include "vga_regs.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
@@ -125,20 +126,19 @@ static void ati_vga_switch_mode(ATIVGAState *s)
 static void ati_cursor_define(ATIVGAState *s)
 {
     uint8_t data[1024];
-    uint8_t *src;
+    uint32_t srcoff;
     int i, j, idx = 0;
 
     if ((s->regs.cur_offset & BIT(31)) || s->cursor_guest_mode) {
         return; /* Do not update cursor if locked or rendered by guest */
     }
     /* FIXME handle cur_hv_offs correctly */
-    src = s->vga.vram_ptr + (s->regs.crtc_offset & 0x07ffffff) +
-          s->regs.cur_offset - (s->regs.cur_hv_offs >> 16) -
-          (s->regs.cur_hv_offs & 0xffff) * 16;
+    srcoff = s->regs.cur_offset -
+        (s->regs.cur_hv_offs >> 16) - (s->regs.cur_hv_offs & 0xffff) * 16;
     for (i = 0; i < 64; i++) {
         for (j = 0; j < 8; j++, idx++) {
-            data[idx] = src[i * 16 + j];
-            data[512 + idx] = src[i * 16 + j + 8];
+            data[idx] = vga_read_byte(&s->vga, srcoff + i * 16 + j);
+            data[512 + idx] = vga_read_byte(&s->vga, srcoff + i * 16 + j + 8);
         }
     }
     if (!s->cursor) {
@@ -180,7 +180,7 @@ static void ati_cursor_invalidate(VGACommonState *vga)
 static void ati_cursor_draw_line(VGACommonState *vga, uint8_t *d, int scr_y)
 {
     ATIVGAState *s = container_of(vga, ATIVGAState, vga);
-    uint8_t *src;
+    uint32_t srcoff;
     uint32_t *dp = (uint32_t *)d;
     int i, j, h;
 
@@ -190,14 +190,13 @@ static void ati_cursor_draw_line(VGACommonState *vga, uint8_t *d, int scr_y)
         return;
     }
     /* FIXME handle cur_hv_offs correctly */
-    src = s->vga.vram_ptr + (s->regs.crtc_offset & 0x07ffffff) +
-          s->cursor_offset + (scr_y - vga->hw_cursor_y) * 16;
+    srcoff = s->cursor_offset + (scr_y - vga->hw_cursor_y) * 16;
     dp = &dp[vga->hw_cursor_x];
     h = ((s->regs.crtc_h_total_disp >> 16) + 1) * 8;
     for (i = 0; i < 8; i++) {
         uint32_t color;
-        uint8_t abits = src[i];
-        uint8_t xbits = src[i + 8];
+        uint8_t abits = vga_read_byte(vga, srcoff + i);
+        uint8_t xbits = vga_read_byte(vga, srcoff + i + 8);
         for (j = 0; j < 8; j++, abits <<= 1, xbits <<= 1) {
             if (abits & BIT(7)) {
                 if (xbits & BIT(7)) {
diff --git a/hw/display/vga-access.h b/hw/display/vga-access.h
new file mode 100644
index 0000000000..c0fbd9958b
--- /dev/null
+++ b/hw/display/vga-access.h
@@ -0,0 +1,49 @@
+/*
+ * QEMU VGA Emulator templates
+ *
+ * Copyright (c) 2003 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+static inline uint8_t vga_read_byte(VGACommonState *vga, uint32_t addr)
+{
+    return vga->vram_ptr[addr & vga->vbe_size_mask];
+}
+
+static inline uint16_t vga_read_word_le(VGACommonState *vga, uint32_t addr)
+{
+    uint32_t offset = addr & vga->vbe_size_mask & ~1;
+    uint16_t *ptr = (uint16_t *)(vga->vram_ptr + offset);
+    return lduw_le_p(ptr);
+}
+
+static inline uint16_t vga_read_word_be(VGACommonState *vga, uint32_t addr)
+{
+    uint32_t offset = addr & vga->vbe_size_mask & ~1;
+    uint16_t *ptr = (uint16_t *)(vga->vram_ptr + offset);
+    return lduw_be_p(ptr);
+}
+
+static inline uint32_t vga_read_dword_le(VGACommonState *vga, uint32_t addr)
+{
+    uint32_t offset = addr & vga->vbe_size_mask & ~3;
+    uint32_t *ptr = (uint32_t *)(vga->vram_ptr + offset);
+    return ldl_le_p(ptr);
+}
diff --git a/hw/display/vga-helpers.h b/hw/display/vga-helpers.h
index 5a752b3f9e..5b6c02faa6 100644
--- a/hw/display/vga-helpers.h
+++ b/hw/display/vga-helpers.h
@@ -21,6 +21,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
+#include "vga-access.h"
 
 static inline void vga_draw_glyph_line(uint8_t *d, uint32_t font_data,
                                        uint32_t xorcol, uint32_t bgcol)
@@ -95,32 +96,6 @@ static void vga_draw_glyph9(uint8_t *d, int linesize,
     } while (--h);
 }
 
-static inline uint8_t vga_read_byte(VGACommonState *vga, uint32_t addr)
-{
-    return vga->vram_ptr[addr & vga->vbe_size_mask];
-}
-
-static inline uint16_t vga_read_word_le(VGACommonState *vga, uint32_t addr)
-{
-    uint32_t offset = addr & vga->vbe_size_mask & ~1;
-    uint16_t *ptr = (uint16_t *)(vga->vram_ptr + offset);
-    return lduw_le_p(ptr);
-}
-
-static inline uint16_t vga_read_word_be(VGACommonState *vga, uint32_t addr)
-{
-    uint32_t offset = addr & vga->vbe_size_mask & ~1;
-    uint16_t *ptr = (uint16_t *)(vga->vram_ptr + offset);
-    return lduw_be_p(ptr);
-}
-
-static inline uint32_t vga_read_dword_le(VGACommonState *vga, uint32_t addr)
-{
-    uint32_t offset = addr & vga->vbe_size_mask & ~3;
-    uint32_t *ptr = (uint32_t *)(vga->vram_ptr + offset);
-    return ldl_le_p(ptr);
-}
-
 /*
  * 4 color mode
  */
-- 
2.27.0

