From patchwork Thu Sep 10 22:57:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 11770097 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 695AF112E for ; Fri, 11 Sep 2020 09:50:17 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1D995206F4 for ; Fri, 11 Sep 2020 09:50:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1D995206F4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=I-love.SAKURA.ne.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 56D996E9EC; Fri, 11 Sep 2020 09:49:41 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by gabe.freedesktop.org (Postfix) with ESMTPS id EF4766E25D for ; Thu, 10 Sep 2020 22:57:20 +0000 (UTC) Received: from fsav110.sakura.ne.jp (fsav110.sakura.ne.jp [27.133.134.237]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 08AMv8qc089110; Fri, 11 Sep 2020 07:57:08 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav110.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav110.sakura.ne.jp); Fri, 11 Sep 2020 07:57:08 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav110.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 08AMv7Ii089106 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 11 Sep 2020 07:57:08 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Subject: [PATCH] fbcon: Fix user font detection test at fbcon_resize(). To: syzbot , george.kennedy@oracle.com, gregkh@linuxfoundation.org, jirislaby@kernel.org, syzkaller-bugs@googlegroups.com References: <00000000000024be1505ad487cbb@google.com> From: Tetsuo Handa Message-ID: Date: Fri, 11 Sep 2020 07:57:06 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <00000000000024be1505ad487cbb@google.com> Content-Language: en-US X-Mailman-Approved-At: Fri, 11 Sep 2020 09:49:36 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-fbdev@vger.kernel.org, b.zolnierkie@samsung.com, daniel.vetter@ffwll.ch, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, natechancellor@gmail.com Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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 --- drivers/video/fbdev/core/fbcon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 66167830fefd..dae7ae7f225a 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2203,7 +2203,7 @@ 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);