From 8d230a5a57512c84545bd6345775e69b4b3b1983 Mon Sep 17 00:00:00 2001 From: Gerd Hoffmann Date: Tue, 7 Feb 2017 10:07:46 +0100 Subject: [PATCH 03/11] cirrus_vga: fix off-by-one in blit_region_is_unsafe RH-Author: Gerd Hoffmann Message-id: <1486462072-32174-2-git-send-email-kraxel@redhat.com> Patchwork-id: 73564 O-Subject: [RHEL-7.4 qemu-kvm PATCH 1/7] cirrus_vga: fix off-by-one in blit_region_is_unsafe Bugzilla: 1418233 RH-Acked-by: Dr. David Alan Gilbert RH-Acked-by: Paolo Bonzini RH-Acked-by: Miroslav Rezanina From: Paolo Bonzini The "max" value is being compared with >=, but addr + width points to the first byte that will _not_ be copied. Laszlo suggested using a "greater than" comparison, instead of subtracting one like it is already done above for the height, so that max remains always positive. The mistake is "safe"---it will reject some blits, but will never cause out-of-bounds writes. Cc: Gerd Hoffmann Signed-off-by: Paolo Bonzini Reviewed-by: Laszlo Ersek Message-id: 1455121059-18280-1-git-send-email-pbonzini@redhat.com Signed-off-by: Gerd Hoffmann (cherry picked from commit d2ba7ecb348d3b996fcd920cf1ca7b72722c1dfd) Signed-off-by: Miroslav Rezanina --- hw/display/cirrus_vga.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c index 717ecdb..c42dfcf 100644 --- a/hw/display/cirrus_vga.c +++ b/hw/display/cirrus_vga.c @@ -272,14 +272,14 @@ static bool blit_region_is_unsafe(struct CirrusVGAState *s, + ((int64_t)s->cirrus_blt_height-1) * pitch; int32_t max = addr + s->cirrus_blt_width; - if (min < 0 || max >= s->vga.vram_size) { + if (min < 0 || max > s->vga.vram_size) { return true; } } else { int64_t max = addr + ((int64_t)s->cirrus_blt_height-1) * pitch + s->cirrus_blt_width; - if (max >= s->vga.vram_size) { + if (max > s->vga.vram_size) { return true; } } -- 1.8.3.1