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From 900ccf5cf6497234e1d3b1e80f4dfa8a60bcfb06 Mon Sep 17 00:00:00 2001
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From: Gerd Hoffmann <kraxel@redhat.com>
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Date: Tue, 7 Feb 2017 10:07:46 +0100
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Subject: [PATCH 2/8] cirrus_vga: fix off-by-one in blit_region_is_unsafe
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RH-Author: Gerd Hoffmann <kraxel@redhat.com>
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Message-id: <1486462072-32174-2-git-send-email-kraxel@redhat.com>
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Patchwork-id: 73564
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O-Subject: [RHEL-7.4 qemu-kvm PATCH 1/7] cirrus_vga: fix off-by-one in blit_region_is_unsafe
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Bugzilla: 1418232
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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From: Paolo Bonzini <pbonzini@redhat.com>
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The "max" value is being compared with >=, but addr + width points to
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the first byte that will _not_ be copied. Laszlo suggested using a
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"greater than" comparison, instead of subtracting one like it is
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already done above for the height, so that max remains always positive.
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The mistake is "safe"---it will reject some blits, but will never cause
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out-of-bounds writes.
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Cc: Gerd Hoffmann <kraxel@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Reviewed-by: Laszlo Ersek <lersek@redhat.com>
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Message-id: 1455121059-18280-1-git-send-email-pbonzini@redhat.com
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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(cherry picked from commit d2ba7ecb348d3b996fcd920cf1ca7b72722c1dfd)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/display/cirrus_vga.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
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index 717ecdb..c42dfcf 100644
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--- a/hw/display/cirrus_vga.c
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+++ b/hw/display/cirrus_vga.c
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@@ -272,14 +272,14 @@ static bool blit_region_is_unsafe(struct CirrusVGAState *s,
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+ ((int64_t)s->cirrus_blt_height-1) * pitch;
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int32_t max = addr
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+ s->cirrus_blt_width;
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- if (min < 0 || max >= s->vga.vram_size) {
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+ if (min < 0 || max > s->vga.vram_size) {
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return true;
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}
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} else {
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int64_t max = addr
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+ ((int64_t)s->cirrus_blt_height-1) * pitch
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+ s->cirrus_blt_width;
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- if (max >= s->vga.vram_size) {
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+ if (max > s->vga.vram_size) {
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return true;
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}
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}
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--
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1.8.3.1
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