From: Gerd Hoffmann Date: Mon, 28 Aug 2017 12:33:07 +0000 (+0200) Subject: vga: fix display update region calculation (split screen) X-Git-Tag: v2.10.1~24 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d6f7f3b0cf4b6c5e7cdff9dfa6d20545e1051375;p=thirdparty%2Fqemu.git vga: fix display update region calculation (split screen) vga display update mis-calculated the region for the dirty bitmap snapshot in case split screen mode is used. This can trigger an assert in cpu_physical_memory_snapshot_get_dirty(). Impact: DoS for privileged guest users. Fixes: CVE-2017-13673 Fixes: fec5e8c92becad223df9d972770522f64aafdb72 Cc: P J P Reported-by: David Buchanan Signed-off-by: Gerd Hoffmann Message-id: 20170828123307.15392-1-kraxel@redhat.com (cherry picked from commit e65294157d4b69393b3f819c99f4f647452b48e3) Signed-off-by: Michael Roth --- diff --git a/hw/display/vga.c b/hw/display/vga.c index 63421f9ee85..ab33668402d 100644 --- a/hw/display/vga.c +++ b/hw/display/vga.c @@ -1628,9 +1628,15 @@ 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 + line_offset * height; vga_sync_dirty_bitmap(s); - snap = memory_region_snapshot_and_clear_dirty(&s->vram, addr1, - line_offset * height, + if (s->line_compare < height) { + /* split screen mode */ + region_start = 0; + } + snap = memory_region_snapshot_and_clear_dirty(&s->vram, region_start, + region_end - region_start, DIRTY_MEMORY_VGA); }