From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36365) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emeao-0001dQ-Qr for qemu-devel@nongnu.org; Fri, 16 Feb 2018 06:54:20 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1emeal-0003fK-IP for qemu-devel@nongnu.org; Fri, 16 Feb 2018 06:54:18 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:33712 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1emeal-0003eN-Co for qemu-devel@nongnu.org; Fri, 16 Feb 2018 06:54:15 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 621244022931 for ; Fri, 16 Feb 2018 11:54:12 +0000 (UTC) From: Gerd Hoffmann Date: Fri, 16 Feb 2018 12:54:07 +0100 Message-Id: <20180216115410.27287-7-kraxel@redhat.com> In-Reply-To: <20180216115410.27287-1-kraxel@redhat.com> References: <20180216115410.27287-1-kraxel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PULL 6/9] 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: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Gerd Hoffmann From: Daniel P. Berrang=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 Reviewed-by: Laszlo Ersek Reviewed-by: Philippe Mathieu-Daud=C3=A9 Message-id: 20180205114938.15784-2-berrange@redhat.com Signed-off-by: Gerd Hoffmann --- ui/vnc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/ui/vnc.c b/ui/vnc.c index e371710f4f..746293ddfa 100644 --- a/ui/vnc.c +++ b/ui/vnc.c @@ -1579,8 +1579,8 @@ 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 2.9.3