@@ -1465,13 +1465,13 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
DisplaySurface *surface = qemu_console_surface(s->con);
int y1, y, update, linesize, y_start, double_scan, mask, depth;
int width, height, shift_control, bwidth, bits;
- ram_addr_t page0, page1;
+ ram_addr_t page0, page1, region_start, region_end;
DirtyBitmapSnapshot *snap = NULL;
int disp_width, multi_scan, multi_run;
uint8_t *d;
uint32_t v, addr1, addr;
vga_draw_line_func *vga_draw_line = NULL;
- bool share_surface;
+ bool share_surface, force_shadow = false;
pixman_format_code_t format;
#ifdef HOST_WORDS_BIGENDIAN
bool byteswap = !s->big_endian_fb;
@@ -1484,6 +1484,15 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
s->get_resolution(s, &width, &height);
disp_width = width;
+ region_start = (s->start_addr * 4);
+ region_end = region_start + s->line_offset * height;
+ if (region_end > s->vbe_size) {
+ /* wraps around (can happen with cirrus vbe modes) */
+ region_start = 0;
+ region_end = s->vbe_size;
+ force_shadow = true;
+ }
+
shift_control = (s->gr[VGA_GFX_MODE] >> 5) & 3;
double_scan = (s->cr[VGA_CRTC_MAX_SCAN] >> 7);
if (shift_control != 1) {
@@ -1523,7 +1532,7 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
format = qemu_default_pixman_format(depth, !byteswap);
if (format) {
share_surface = dpy_gfx_check_format(s->con, format)
- && !s->force_shadow;
+ && !s->force_shadow && !force_shadow;
} else {
share_surface = false;
}
@@ -1627,8 +1636,6 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
y1 = 0;
if (!full_update) {
- ram_addr_t region_start = addr1;
- ram_addr_t region_end = addr1 + s->line_offset * height;
vga_sync_dirty_bitmap(s);
if (s->line_compare < height) {
/* split screen mode */
@@ -1651,10 +1658,17 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
addr = (addr & ~0x8000) | ((y1 & 2) << 14);
}
update = full_update;
- page0 = addr;
- page1 = addr + bwidth - 1;
+ page0 = addr & s->vbe_size_mask;
+ page1 = (addr + bwidth - 1) & s->vbe_size_mask;
if (full_update) {
update = 1;
+ } else if (page1 < page0) {
+ /* scanline wraps from end of video memory to the start */
+ assert(force_shadow);
+ update = memory_region_snapshot_get_dirty(&s->vram, snap,
+ page0, 0);
+ update |= memory_region_snapshot_get_dirty(&s->vram, snap,
+ page1, 0);
} else {
update = memory_region_snapshot_get_dirty(&s->vram, snap,
page0, page1 - page0);
Commit "3d90c62548 vga: stop passing pointers to vga_draw_line* functions" is incomplete. It doesn't handle the case that the vga rendering code tries to create a shared surface, i.e. a pixman image backed by vga video memory. That can not work in case the guest display wraps from end of video memory to the start. So force shadowing in that case. Also adjust the snapshot region calculation. Can trigger with cirrus only, when programming vbe modes using the bochs api (stdvga, also qxl and virtio-vga in vga compat mode) wrap arounds can't happen. Fixes: CVE-2017-13672 Fixes: 3d90c6254863693a6b13d918d2b8682e08bbc681 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: 20171010141323.14049-3-kraxel@redhat.com --- hw/display/vga.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-)