From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48544) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTXSb-0003PG-OR for qemu-devel@nongnu.org; Wed, 10 Feb 2016 11:17:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aTXSY-00084S-H5 for qemu-devel@nongnu.org; Wed, 10 Feb 2016 11:17:45 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36605) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTXSY-00084M-Bl for qemu-devel@nongnu.org; Wed, 10 Feb 2016 11:17:42 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id 9F5955A44 for ; Wed, 10 Feb 2016 16:17:41 +0000 (UTC) From: Paolo Bonzini Date: Wed, 10 Feb 2016 17:17:39 +0100 Message-Id: <1455121059-18280-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH v2] cirrus_vga: fix off-by-one in blit_region_is_unsafe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: lersek@redhat.com, Gerd Hoffmann 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 --- 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 b6ce1c8..57b91a7 100644 --- a/hw/display/cirrus_vga.c +++ b/hw/display/cirrus_vga.c @@ -276,14 +276,14 @@ 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; } } -- 2.5.0