From patchwork Mon Mar 6 09:49:21 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Samuel Thibault X-Patchwork-Id: 13160769 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3EC3FC61DA4 for ; Mon, 6 Mar 2023 09:49:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229699AbjCFJt0 (ORCPT ); Mon, 6 Mar 2023 04:49:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229540AbjCFJtZ (ORCPT ); Mon, 6 Mar 2023 04:49:25 -0500 Received: from sonata.ens-lyon.org (sonata.ens-lyon.org [140.77.166.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AE608C651; Mon, 6 Mar 2023 01:49:24 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by sonata.ens-lyon.org (Postfix) with ESMTP id BFA9E20137; Mon, 6 Mar 2023 10:49:22 +0100 (CET) Received: from sonata.ens-lyon.org ([127.0.0.1]) by localhost (sonata.ens-lyon.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hErAdg_uF3sj; Mon, 6 Mar 2023 10:49:22 +0100 (CET) Received: from begin (nat-inria-interne-52-gw-01-bso.bordeaux.inria.fr [194.199.1.52]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by sonata.ens-lyon.org (Postfix) with ESMTPSA id 455092012C; Mon, 6 Mar 2023 10:49:22 +0100 (CET) Received: from samy by begin with local (Exim 4.96) (envelope-from ) id 1pZ7T7-0001Rf-1i; Mon, 06 Mar 2023 10:49:21 +0100 Date: Mon, 6 Mar 2023 10:49:21 +0100 From: Samuel Thibault To: gregkh@linuxfoundation.org Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Sanan Hasanov , Samuel Thibault , keescook@chromium.org, syzbot+3af17071816b61e807ed@syzkaller.appspotmail.com, akpm@linux-foundation.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Jiri Slaby Subject: [PATCH] VT: Protect KD_FONT_OP_GET_TALL from unbound access Message-ID: <20230306094921.tik5ewne4ft6mfpo@begin> Mail-Followup-To: Samuel Thibault , gregkh@linuxfoundation.org, linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Sanan Hasanov , keescook@chromium.org, syzbot+3af17071816b61e807ed@syzkaller.appspotmail.com, akpm@linux-foundation.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Jiri Slaby MIME-Version: 1.0 Content-Disposition: inline Organization: I am not organized User-Agent: NeoMutt/20170609 (1.8.3) Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org In ioctl(KD_FONT_OP_GET_TALL), userland tells through op->height which vpitch should be used to copy over the font. In con_font_get, we were not checking that it is within the maximum height value, and thus userland could make the vc->vc_sw->con_font_get(vc, &font, vpitch); call possibly overflow the allocated max_font_size bytes, and the copy_to_user(op->data, font.data, c) call possibly read out of that allocated buffer. By checking vpitch against max_font_height, the max_font_size buffer will always be large enough for the vc->vc_sw->con_font_get(vc, &font, vpitch) call (since we already prevent loading a font larger than that), and c = (font.width+7)/8 * vpitch * font.charcount will always remain below max_font_size. Fixes: 24d69384bcd3 ("VT: Add KD_FONT_OP_SET/GET_TALL operations") Reported-by: syzbot+3af17071816b61e807ed@syzkaller.appspotmail.com Signed-off-by: Samuel Thibault Reviewed-by: Jiri Slaby diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 57a5c23b51d4..3c2ea9c098f7 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -4545,6 +4545,9 @@ static int con_font_get(struct vc_data *vc, struct console_font_op *op) int c; unsigned int vpitch = op->op == KD_FONT_OP_GET_TALL ? op->height : 32; + if (vpitch > max_font_height) + return -EINVAL; + if (op->data) { font.data = kvmalloc(max_font_size, GFP_KERNEL); if (!font.data)