From patchwork Mon Sep 21 16:28:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "gregkh@linuxfoundation.org" X-Patchwork-Id: 309482 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A917BC43465 for ; Mon, 21 Sep 2020 16:36:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AFFB239A1 for ; Mon, 21 Sep 2020 16:36:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600706182; bh=+OOrdhldkbOwXGbhXZnFEBxmS8ERh3cGw8dgn8ouTXs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=D0R1HYQYo5qmMrSPnISTNkiZbfkqkiolXbvATv9NB763rF3VsLXdOZg/TfdGOwAOG CpkI549vGigAbtyH4Rj5KXjexB9/idTgU8AUteeJStOymP1nMx5x1TRcaqQUoy78QX 4eMRkJIsmCBjRxHkGiV+cXxGht7050Vd9T1HDcns= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728941AbgIUQgV (ORCPT ); Mon, 21 Sep 2020 12:36:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:35952 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728950AbgIUQgQ (ORCPT ); Mon, 21 Sep 2020 12:36:16 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 401582396F; Mon, 21 Sep 2020 16:36:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600706175; bh=+OOrdhldkbOwXGbhXZnFEBxmS8ERh3cGw8dgn8ouTXs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AQLQ8LLGN/fjPHsWRCagCm2d8p/kevHmz2JH39Hs00lnT52vU6QzzjD1VSYrt+/C+ ZeFKG74ErWG0P40AwwHgzji6tPUTjhYWUg3IQy0qYrAgQkVwCcIAIVPyB4nV363smL /XzVvw5aH44bR9ziq5g8YTTFk2yEzaB3rqvxyVZ8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot , Tetsuo Handa , George Kennedy , Sasha Levin Subject: [PATCH 4.9 60/70] fbcon: Fix user font detection test at fbcon_resize(). Date: Mon, 21 Sep 2020 18:28:00 +0200 Message-Id: <20200921162037.878641922@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200921162035.136047591@linuxfoundation.org> References: <20200921162035.136047591@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Tetsuo Handa [ Upstream commit ec0972adecb391a8d8650832263a4790f3bfb4df ] syzbot is reporting OOB read at fbcon_resize() [1], for commit 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") is by error using registered_fb[con2fb_map[vc->vc_num]]->fbcon_par->p->userfont (which was set to non-zero) instead of fb_display[vc->vc_num].userfont (which remains zero for that display). We could remove tricky userfont flag [2], for we can determine it by comparing address of the font data and addresses of built-in font data. But since that commit is failing to fix the original OOB read [3], this patch keeps the change minimal in case we decide to revert altogether. [1] https://syzkaller.appspot.com/bug?id=ebcbbb6576958a496500fee9cf7aa83ea00b5920 [2] https://syzkaller.appspot.com/text?tag=Patch&x=14030853900000 [3] https://syzkaller.appspot.com/bug?id=6fba8c186d97cf1011ab17660e633b1cc4e080c9 Reported-by: syzbot Signed-off-by: Tetsuo Handa Fixes: 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") Cc: George Kennedy Link: https://lore.kernel.org/r/f6e3e611-8704-1263-d163-f52c906a4f06@I-love.SAKURA.ne.jp Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/video/console/fbcon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c index fedf50e091bab..4b7d0f9a820aa 100644 --- a/drivers/video/console/fbcon.c +++ b/drivers/video/console/fbcon.c @@ -1943,7 +1943,7 @@ static int fbcon_resize(struct vc_data *vc, unsigned int width, struct fb_var_screeninfo var = info->var; int x_diff, y_diff, virt_w, virt_h, virt_fw, virt_fh; - if (ops->p && ops->p->userfont && FNTSIZE(vc->vc_font.data)) { + if (p->userfont && FNTSIZE(vc->vc_font.data)) { int size; int pitch = PITCH(vc->vc_font.width);