From e56700784b7585dddff0713ea52b2b00b8531b7f Mon Sep 17 00:00:00 2001

From: Gerd Hoffmann <kraxel@redhat.com>

Date: Thu, 5 Oct 2017 14:51:19 +0200

Subject: [PATCH 23/27] vga: stop passing pointers to vga_draw_line* functions

RH-Author: Gerd Hoffmann <kraxel@redhat.com>

Message-id: <20171005145119.15277-8-kraxel@redhat.com>

Patchwork-id: 76828

O-Subject: [RHEL-7.5 qemu-kvm PATCH 7/7] vga: stop passing pointers to vga_draw_line* functions

Bugzilla: 1486642

RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

RH-Acked-by: Thomas Huth <thuth@redhat.com>

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

Instead pass around the address (aka offset into vga memory).

Add vga_read_* helper functions which apply vbe_size_mask to

the address, to make sure the address stays within the valid

range, similar to the cirrus blitter fixes (commits ffaf857778

and 026aeffcb4).

Impact:  DoS for privileged guest users.  qemu crashes with

a segfault, when hitting the guard page after vga memory

allocation, while reading vga memory for display updates.

Fixes: CVE-2017-13672

Cc: P J P <ppandit@redhat.com>

Reported-by: David Buchanan <d@vidbuchanan.co.uk>

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

Message-id: 20170828122906.18993-1-kraxel@redhat.com

(cherry picked from commit 3d90c6254863693a6b13d918d2b8682e08bbc681)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 hw/display/vga-helpers.h | 202 ++++++++++++++++++++++++++---------------------

 hw/display/vga.c         |   5 +-

 hw/display/vga_int.h     |   1 +

 3 files changed, 114 insertions(+), 94 deletions(-)

diff --git a/hw/display/vga-helpers.h b/hw/display/vga-helpers.h

index 94f6de2..5a752b3 100644

--- a/hw/display/vga-helpers.h

+++ b/hw/display/vga-helpers.h

@@ -95,20 +95,46 @@ 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

  */

-static void vga_draw_line2(VGACommonState *s1, uint8_t *d,

-                           const uint8_t *s, int width)

+static void vga_draw_line2(VGACommonState *vga, uint8_t *d,

+                           uint32_t addr, int width)

 {

     uint32_t plane_mask, *palette, data, v;

     int x;

-    palette = s1->last_palette;

-    plane_mask = mask16[s1->ar[VGA_ATC_PLANE_ENABLE] & 0xf];

+    palette = vga->last_palette;

+    plane_mask = mask16[vga->ar[VGA_ATC_PLANE_ENABLE] & 0xf];

     width >>= 3;

     for(x = 0; x < width; x++) {

-        data = ((uint32_t *)s)[0];

+        data = vga_read_dword_le(vga, addr);

         data &= plane_mask;

         v = expand2[GET_PLANE(data, 0)];

         v |= expand2[GET_PLANE(data, 2)] << 2;

@@ -124,7 +150,7 @@ static void vga_draw_line2(VGACommonState *s1, uint8_t *d,

         ((uint32_t *)d)[6] = palette[(v >> 4) & 0xf];

         ((uint32_t *)d)[7] = palette[(v >> 0) & 0xf];

         d += 32;

-        s += 4;

+        addr += 4;

     }

 }

@@ -134,17 +160,17 @@ static void vga_draw_line2(VGACommonState *s1, uint8_t *d,

 /*

  * 4 color mode, dup2 horizontal

  */

-static void vga_draw_line2d2(VGACommonState *s1, uint8_t *d,

-                             const uint8_t *s, int width)

+static void vga_draw_line2d2(VGACommonState *vga, uint8_t *d,

+                             uint32_t addr, int width)

 {

     uint32_t plane_mask, *palette, data, v;

     int x;

-    palette = s1->last_palette;

-    plane_mask = mask16[s1->ar[VGA_ATC_PLANE_ENABLE] & 0xf];

+    palette = vga->last_palette;

+    plane_mask = mask16[vga->ar[VGA_ATC_PLANE_ENABLE] & 0xf];

     width >>= 3;

     for(x = 0; x < width; x++) {

-        data = ((uint32_t *)s)[0];

+        data = vga_read_dword_le(vga, addr);

         data &= plane_mask;

         v = expand2[GET_PLANE(data, 0)];

         v |= expand2[GET_PLANE(data, 2)] << 2;

@@ -160,24 +186,24 @@ static void vga_draw_line2d2(VGACommonState *s1, uint8_t *d,

         PUT_PIXEL2(d, 6, palette[(v >> 4) & 0xf]);

         PUT_PIXEL2(d, 7, palette[(v >> 0) & 0xf]);

         d += 64;

-        s += 4;

+        addr += 4;

     }

 }

 /*

  * 16 color mode

  */

-static void vga_draw_line4(VGACommonState *s1, uint8_t *d,

-                           const uint8_t *s, int width)

+static void vga_draw_line4(VGACommonState *vga, uint8_t *d,

+                           uint32_t addr, int width)

 {

     uint32_t plane_mask, data, v, *palette;

     int x;

-    palette = s1->last_palette;

-    plane_mask = mask16[s1->ar[VGA_ATC_PLANE_ENABLE] & 0xf];

+    palette = vga->last_palette;

+    plane_mask = mask16[vga->ar[VGA_ATC_PLANE_ENABLE] & 0xf];

     width >>= 3;

     for(x = 0; x < width; x++) {

-        data = ((uint32_t *)s)[0];

+        data = vga_read_dword_le(vga, addr);

         data &= plane_mask;

         v = expand4[GET_PLANE(data, 0)];

         v |= expand4[GET_PLANE(data, 1)] << 1;

@@ -192,24 +218,24 @@ static void vga_draw_line4(VGACommonState *s1, uint8_t *d,

         ((uint32_t *)d)[6] = palette[(v >> 4) & 0xf];

         ((uint32_t *)d)[7] = palette[(v >> 0) & 0xf];

         d += 32;

-        s += 4;

+        addr += 4;

     }

 }

 /*

  * 16 color mode, dup2 horizontal

  */

-static void vga_draw_line4d2(VGACommonState *s1, uint8_t *d,

-                             const uint8_t *s, int width)

+static void vga_draw_line4d2(VGACommonState *vga, uint8_t *d,

+                             uint32_t addr, int width)

 {

     uint32_t plane_mask, data, v, *palette;

     int x;

-    palette = s1->last_palette;

-    plane_mask = mask16[s1->ar[VGA_ATC_PLANE_ENABLE] & 0xf];

+    palette = vga->last_palette;

+    plane_mask = mask16[vga->ar[VGA_ATC_PLANE_ENABLE] & 0xf];

     width >>= 3;

     for(x = 0; x < width; x++) {

-        data = ((uint32_t *)s)[0];

+        data = vga_read_dword_le(vga, addr);

         data &= plane_mask;

         v = expand4[GET_PLANE(data, 0)];

         v |= expand4[GET_PLANE(data, 1)] << 1;

@@ -224,7 +250,7 @@ static void vga_draw_line4d2(VGACommonState *s1, uint8_t *d,

         PUT_PIXEL2(d, 6, palette[(v >> 4) & 0xf]);

         PUT_PIXEL2(d, 7, palette[(v >> 0) & 0xf]);

         d += 64;

-        s += 4;

+        addr += 4;

     }

 }

@@ -233,21 +259,21 @@ static void vga_draw_line4d2(VGACommonState *s1, uint8_t *d,

  *

  * XXX: add plane_mask support (never used in standard VGA modes)

  */

-static void vga_draw_line8d2(VGACommonState *s1, uint8_t *d,

-                             const uint8_t *s, int width)

+static void vga_draw_line8d2(VGACommonState *vga, uint8_t *d,

+                             uint32_t addr, int width)

 {

     uint32_t *palette;

     int x;

-    palette = s1->last_palette;

+    palette = vga->last_palette;

     width >>= 3;

     for(x = 0; x < width; x++) {

-        PUT_PIXEL2(d, 0, palette[s[0]]);

-        PUT_PIXEL2(d, 1, palette[s[1]]);

-        PUT_PIXEL2(d, 2, palette[s[2]]);

-        PUT_PIXEL2(d, 3, palette[s[3]]);

+        PUT_PIXEL2(d, 0, palette[vga_read_byte(vga, addr + 0)]);

+        PUT_PIXEL2(d, 1, palette[vga_read_byte(vga, addr + 1)]);

+        PUT_PIXEL2(d, 2, palette[vga_read_byte(vga, addr + 2)]);

+        PUT_PIXEL2(d, 3, palette[vga_read_byte(vga, addr + 3)]);

         d += 32;

-        s += 4;

+        addr += 4;

     }

 }

@@ -256,63 +282,63 @@ static void vga_draw_line8d2(VGACommonState *s1, uint8_t *d,

  *

  * XXX: add plane_mask support (never used in standard VGA modes)

  */

-static void vga_draw_line8(VGACommonState *s1, uint8_t *d,

-                           const uint8_t *s, int width)

+static void vga_draw_line8(VGACommonState *vga, uint8_t *d,

+                           uint32_t addr, int width)

 {

     uint32_t *palette;

     int x;

-    palette = s1->last_palette;

+    palette = vga->last_palette;

     width >>= 3;

     for(x = 0; x < width; x++) {

-        ((uint32_t *)d)[0] = palette[s[0]];

-        ((uint32_t *)d)[1] = palette[s[1]];

-        ((uint32_t *)d)[2] = palette[s[2]];

-        ((uint32_t *)d)[3] = palette[s[3]];

-        ((uint32_t *)d)[4] = palette[s[4]];

-        ((uint32_t *)d)[5] = palette[s[5]];

-        ((uint32_t *)d)[6] = palette[s[6]];

-        ((uint32_t *)d)[7] = palette[s[7]];

+        ((uint32_t *)d)[0] = palette[vga_read_byte(vga, addr + 0)];

+        ((uint32_t *)d)[1] = palette[vga_read_byte(vga, addr + 1)];

+        ((uint32_t *)d)[2] = palette[vga_read_byte(vga, addr + 2)];

+        ((uint32_t *)d)[3] = palette[vga_read_byte(vga, addr + 3)];

+        ((uint32_t *)d)[4] = palette[vga_read_byte(vga, addr + 4)];

+        ((uint32_t *)d)[5] = palette[vga_read_byte(vga, addr + 5)];

+        ((uint32_t *)d)[6] = palette[vga_read_byte(vga, addr + 6)];

+        ((uint32_t *)d)[7] = palette[vga_read_byte(vga, addr + 7)];

         d += 32;

-        s += 8;

+        addr += 8;

     }

 }

 /*

  * 15 bit color

  */

-static void vga_draw_line15_le(VGACommonState *s1, uint8_t *d,

-                               const uint8_t *s, int width)

+static void vga_draw_line15_le(VGACommonState *vga, uint8_t *d,

+                               uint32_t addr, int width)

 {

     int w;

     uint32_t v, r, g, b;

     w = width;

     do {

-        v = lduw_le_p((void *)s);

+        v = vga_read_word_le(vga, addr);

         r = (v >> 7) & 0xf8;

         g = (v >> 2) & 0xf8;

         b = (v << 3) & 0xf8;

         ((uint32_t *)d)[0] = rgb_to_pixel32(r, g, b);

-        s += 2;

+        addr += 2;

         d += 4;

     } while (--w != 0);

 }

-static void vga_draw_line15_be(VGACommonState *s1, uint8_t *d,

-                               const uint8_t *s, int width)

+static void vga_draw_line15_be(VGACommonState *vga, uint8_t *d,

+                               uint32_t addr, int width)

 {

     int w;

     uint32_t v, r, g, b;

     w = width;

     do {

-        v = lduw_be_p((void *)s);

+        v = vga_read_word_be(vga, addr);

         r = (v >> 7) & 0xf8;

         g = (v >> 2) & 0xf8;

         b = (v << 3) & 0xf8;

         ((uint32_t *)d)[0] = rgb_to_pixel32(r, g, b);

-        s += 2;

+        addr += 2;

         d += 4;

     } while (--w != 0);

 }

@@ -320,38 +346,38 @@ static void vga_draw_line15_be(VGACommonState *s1, uint8_t *d,

 /*

  * 16 bit color

  */

-static void vga_draw_line16_le(VGACommonState *s1, uint8_t *d,

-                               const uint8_t *s, int width)

+static void vga_draw_line16_le(VGACommonState *vga, uint8_t *d,

+                               uint32_t addr, int width)

 {

     int w;

     uint32_t v, r, g, b;

     w = width;

     do {

-        v = lduw_le_p((void *)s);

+        v = vga_read_word_le(vga, addr);

         r = (v >> 8) & 0xf8;

         g = (v >> 3) & 0xfc;

         b = (v << 3) & 0xf8;

         ((uint32_t *)d)[0] = rgb_to_pixel32(r, g, b);

-        s += 2;

+        addr += 2;

         d += 4;

     } while (--w != 0);

 }

-static void vga_draw_line16_be(VGACommonState *s1, uint8_t *d,

-                               const uint8_t *s, int width)

+static void vga_draw_line16_be(VGACommonState *vga, uint8_t *d,

+                               uint32_t addr, int width)

 {

     int w;

     uint32_t v, r, g, b;

     w = width;

     do {

-        v = lduw_be_p((void *)s);

+        v = vga_read_word_be(vga, addr);

         r = (v >> 8) & 0xf8;

         g = (v >> 3) & 0xfc;

         b = (v << 3) & 0xf8;

         ((uint32_t *)d)[0] = rgb_to_pixel32(r, g, b);

-        s += 2;

+        addr += 2;

         d += 4;

     } while (--w != 0);

 }

@@ -359,36 +385,36 @@ static void vga_draw_line16_be(VGACommonState *s1, uint8_t *d,

 /*

  * 24 bit color

  */

-static void vga_draw_line24_le(VGACommonState *s1, uint8_t *d,

-                               const uint8_t *s, int width)

+static void vga_draw_line24_le(VGACommonState *vga, uint8_t *d,

+                               uint32_t addr, int width)

 {

     int w;

     uint32_t r, g, b;

     w = width;

     do {

-        b = s[0];

-        g = s[1];

-        r = s[2];

+        b = vga_read_byte(vga, addr + 0);

+        g = vga_read_byte(vga, addr + 1);

+        r = vga_read_byte(vga, addr + 2);

         ((uint32_t *)d)[0] = rgb_to_pixel32(r, g, b);

-        s += 3;

+        addr += 3;

         d += 4;

     } while (--w != 0);

 }

-static void vga_draw_line24_be(VGACommonState *s1, uint8_t *d,

-                               const uint8_t *s, int width)

+static void vga_draw_line24_be(VGACommonState *vga, uint8_t *d,

+                               uint32_t addr, int width)

 {

     int w;

     uint32_t r, g, b;

     w = width;

     do {

-        r = s[0];

-        g = s[1];

-        b = s[2];

+        r = vga_read_byte(vga, addr + 0);

+        g = vga_read_byte(vga, addr + 1);

+        b = vga_read_byte(vga, addr + 2);

         ((uint32_t *)d)[0] = rgb_to_pixel32(r, g, b);

-        s += 3;

+        addr += 3;

         d += 4;

     } while (--w != 0);

 }

@@ -396,44 +422,36 @@ static void vga_draw_line24_be(VGACommonState *s1, uint8_t *d,

 /*

  * 32 bit color

  */

-static void vga_draw_line32_le(VGACommonState *s1, uint8_t *d,

-                               const uint8_t *s, int width)

+static void vga_draw_line32_le(VGACommonState *vga, uint8_t *d,

+                               uint32_t addr, int width)

 {

-#ifndef HOST_WORDS_BIGENDIAN

-    memcpy(d, s, width * 4);

-#else

     int w;

     uint32_t r, g, b;

     w = width;

     do {

-        b = s[0];

-        g = s[1];

-        r = s[2];

+        b = vga_read_byte(vga, addr + 0);

+        g = vga_read_byte(vga, addr + 1);

+        r = vga_read_byte(vga, addr + 2);

         ((uint32_t *)d)[0] = rgb_to_pixel32(r, g, b);

-        s += 4;

+        addr += 4;

         d += 4;

     } while (--w != 0);

-#endif

 }

-static void vga_draw_line32_be(VGACommonState *s1, uint8_t *d,

-                               const uint8_t *s, int width)

+static void vga_draw_line32_be(VGACommonState *vga, uint8_t *d,

+                               uint32_t addr, int width)

 {

-#ifdef HOST_WORDS_BIGENDIAN

-    memcpy(d, s, width * 4);

-#else

     int w;

     uint32_t r, g, b;

     w = width;

     do {

-        r = s[1];

-        g = s[2];

-        b = s[3];

+        r = vga_read_byte(vga, addr + 1);

+        g = vga_read_byte(vga, addr + 2);

+        b = vga_read_byte(vga, addr + 3);

         ((uint32_t *)d)[0] = rgb_to_pixel32(r, g, b);

-        s += 4;

+        addr += 4;

         d += 4;

     } while (--w != 0);

-#endif

 }

diff --git a/hw/display/vga.c b/hw/display/vga.c

index 4618823..5b0b864 100644

--- a/hw/display/vga.c

+++ b/hw/display/vga.c

@@ -1045,7 +1045,7 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val)

 }

 typedef void vga_draw_line_func(VGACommonState *s1, uint8_t *d,

-                                const uint8_t *s, int width);

+                                uint32_t srcaddr, int width);

 #include "vga-helpers.h"

@@ -1682,7 +1682,7 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)

             if (page1 > page_max)

                 page_max = page1;

             if (!(is_buffer_shared(surface))) {

-                vga_draw_line(s, d, s->vram_ptr + addr, width);

+                vga_draw_line(s, d, addr, width);

                 if (s->cursor_draw_line)

                     s->cursor_draw_line(s, d, y);

             }

@@ -2162,6 +2162,7 @@ void vga_common_init(VGACommonState *s)

     if (!s->vbe_size) {

         s->vbe_size = s->vram_size;

     }

+    s->vbe_size_mask = s->vbe_size - 1;

     s->is_vbe_vmstate = 1;

     memory_region_init_ram(&s->vram, "vga.vram", s->vram_size);

diff --git a/hw/display/vga_int.h b/hw/display/vga_int.h

index 7c758ac..94add2f 100644

--- a/hw/display/vga_int.h

+++ b/hw/display/vga_int.h

@@ -94,6 +94,7 @@ typedef struct VGACommonState {

     uint32_t vram_size;

     uint32_t vram_size_mb; /* property */

     uint32_t vbe_size;

+    uint32_t vbe_size_mask;

     uint32_t latch;

     MemoryRegion *chain4_alias;

     uint8_t sr_index;

-- 

1.8.3.1