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From e65294157d4b69393b3f819c99f4f647452b48e3 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Mon, 28 Aug 2017 14:33:07 +0200
Subject: [PATCH] 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 <ppandit@redhat.com>
Reported-by: David Buchanan <d@vidbuchanan.co.uk>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20170828123307.15392-1-kraxel@redhat.com
Upstream-Status: Backport
[https://git.qemu.org/?p=qemu.git;a=commit;h=e65294157d4b69393b3f819c99f4f647452b48e3]
CVE: CVE-2017-13673
Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
---
hw/display/vga.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/hw/display/vga.c b/hw/display/vga.c
index 3433102..ad7a465 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);
}
--
2.7.4
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