From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54238) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eifHV-000489-0s for qemu-devel@nongnu.org; Mon, 05 Feb 2018 06:49:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eifHQ-0008D8-CM for qemu-devel@nongnu.org; Mon, 05 Feb 2018 06:49:53 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41188) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eifHQ-0008Ck-7U for qemu-devel@nongnu.org; Mon, 05 Feb 2018 06:49:48 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 687EE61476 for ; Mon, 5 Feb 2018 11:49:47 +0000 (UTC) From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Date: Mon, 5 Feb 2018 11:49:35 +0000 Message-Id: <20180205114938.15784-2-berrange@redhat.com> In-Reply-To: <20180205114938.15784-1-berrange@redhat.com> References: <20180205114938.15784-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PATCH 1/4] ui: avoid risk of 32-bit int overflow in VNC buffer check List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Gerd Hoffmann , Laszlo Ersek , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= For very large framebuffers, it is theoretically possible for the result of 'vs->throttle_output_offset * VNC_THROTTLE_OUTPUT_LIMIT_SCALE' to exceed the size of a 32-bit int. For this to happen in practice, the video RAM would have to be set to a large enough value, which is not likely today. None the less we can be paranoid against future growth by using division instead of multiplication when checking the limits. Reported-by: Laszlo Ersek Signed-off-by: Daniel P. Berrang=C3=A9 --- ui/vnc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/ui/vnc.c b/ui/vnc.c index 93731accb6..e14e524764 100644 --- a/ui/vnc.c +++ b/ui/vnc.c @@ -1572,8 +1572,8 @@ void vnc_write(VncState *vs, const void *data, size= _t len) * handshake, or from the job thread's VncState clone */ if (vs->throttle_output_offset !=3D 0 && - vs->output.offset > (vs->throttle_output_offset * - VNC_THROTTLE_OUTPUT_LIMIT_SCALE)) { + (vs->output.offset / VNC_THROTTLE_OUTPUT_LIMIT_SCALE) > + vs->throttle_output_offset) { trace_vnc_client_output_limit(vs, vs->ioc, vs->output.offset, vs->throttle_output_offset); vnc_disconnect_start(vs); --=20 2.14.3