Blame SOURCES/kvm-vga-fix-display-update-region-calculation-split-scre.patch

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From 5a5e2e2d4f7cc2fd67fa970584f06a29ba69fc3a Mon Sep 17 00:00:00 2001
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From: Gerd Hoffmann <kraxel@redhat.com>
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Date: Thu, 5 Oct 2017 09:49:33 +0200
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Subject: [PATCH 02/69] vga: fix display update region calculation (split
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 screen)
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RH-Author: Gerd Hoffmann <kraxel@redhat.com>
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Message-id: <20171005094933.19435-2-kraxel@redhat.com>
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Patchwork-id: 76816
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O-Subject: [RHV7.5 qemu-kvm-rhev PATCH 1/1] vga: fix display update region calculation (split screen)
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Bugzilla: 1486648
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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vga display update mis-calculated the region for the dirty bitmap
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snapshot in case split screen mode is used.  This can trigger an
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assert in cpu_physical_memory_snapshot_get_dirty().
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Impact:  DoS for privileged guest users.
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Fixes: CVE-2017-13673
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Fixes: fec5e8c92becad223df9d972770522f64aafdb72
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Cc: P J P <ppandit@redhat.com>
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Reported-by: David Buchanan <d@vidbuchanan.co.uk>
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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Message-id: 20170828123307.15392-1-kraxel@redhat.com
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(cherry picked from commit e65294157d4b69393b3f819c99f4f647452b48e3)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 hw/display/vga.c | 10 ++++++++--
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 1 file changed, 8 insertions(+), 2 deletions(-)
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diff --git a/hw/display/vga.c b/hw/display/vga.c
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index 4c2ee0b..497c823 100644
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--- a/hw/display/vga.c
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+++ b/hw/display/vga.c
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@@ -1628,9 +1628,15 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
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     y1 = 0;
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     if (!full_update) {
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+        ram_addr_t region_start = addr1;
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+        ram_addr_t region_end = addr1 + line_offset * height;
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         vga_sync_dirty_bitmap(s);
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-        snap = memory_region_snapshot_and_clear_dirty(&s->vram, addr1,
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-                                                      line_offset * height,
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+        if (s->line_compare < height) {
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+            /* split screen mode */
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+            region_start = 0;
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+        }
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+        snap = memory_region_snapshot_and_clear_dirty(&s->vram, region_start,
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+                                                      region_end - region_start,
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                                                       DIRTY_MEMORY_VGA);
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     }
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-- 
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1.8.3.1
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