From mboxrd@z Thu Jan 1 00:00:00 1970 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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 2ABB3C432BE for ; Wed, 1 Sep 2021 01:15:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0DFFC61051 for ; Wed, 1 Sep 2021 01:15:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241328AbhIABQ3 (ORCPT ); Tue, 31 Aug 2021 21:16:29 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:63035 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234036AbhIABQX (ORCPT ); Tue, 31 Aug 2021 21:16:23 -0400 Received: from fsav415.sakura.ne.jp (fsav415.sakura.ne.jp [133.242.250.114]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 1811ElQO061022; Wed, 1 Sep 2021 10:14:47 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav415.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav415.sakura.ne.jp); Wed, 01 Sep 2021 10:14:47 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav415.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 1811EkXj061015 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Wed, 1 Sep 2021 10:14:46 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: [PATCH v2] fbmem: don't allow too huge resolutions To: Daniel Vetter , Geert Uytterhoeven Cc: syzbot , Andrew Morton , Bartlomiej Zolnierkiewicz , Colin King , DRI Development , Linux Fbdev development list , Linux Kernel Mailing List , Masahiro Yamada , syzkaller-bugs , Randy Dunlap References: <000000000000815b9605c70e74f8@google.com> <131b24e5-ee31-6f7b-42b4-c34583711913@infradead.org> <2fccb5d3-191c-924e-159f-1c9d423e282f@i-love.sakura.ne.jp> <339bfb21-8e80-c7d9-46dd-c416f87c50c0@infradead.org> <535e404d-03bf-8e7a-b296-132a2a98c599@i-love.sakura.ne.jp> <5c6d2b95-31d7-0d59-5e62-2593d9a0e1fe@i-love.sakura.ne.jp> From: Tetsuo Handa Message-ID: <750ed1ae-de80-b232-4aea-79d60c212fab@i-love.sakura.ne.jp> Date: Wed, 1 Sep 2021 10:14:43 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org syzbot is reporting page fault at vga16fb_fillrect() [1], for vga16fb_check_var() is failing to detect multiplication overflow. if (vxres * vyres > maxmem) { vyres = maxmem / vxres; if (vyres < yres) return -ENOMEM; } Since no module would accept too huge resolutions where multiplication overflow happens, let's reject in the common path. Link: https://syzkaller.appspot.com/bug?extid=04168c8063cfdde1db5e [1] Reported-by: syzbot Debugged-by: Randy Dunlap Signed-off-by: Tetsuo Handa --- Changes in v2: Use check_mul_overflow(), suggested by Geert Uytterhoeven . drivers/video/fbdev/core/fbmem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 1c855145711b..53d23b3d010c 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -962,6 +962,7 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var) struct fb_var_screeninfo old_var; struct fb_videomode mode; struct fb_event event; + u32 unused; if (var->activate & FB_ACTIVATE_INV_MODE) { struct fb_videomode mode1, mode2; @@ -1008,6 +1009,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var) if (var->xres < 8 || var->yres < 8) return -EINVAL; + /* Too huge resolution causes multiplication overflow. */ + if (check_mul_overflow(var->xres, var->yres, &unused) || + check_mul_overflow(var->xres_virtual, var->yres_virtual, &unused)) + return -EINVAL; + ret = info->fbops->fb_check_var(var, info); if (ret) -- 2.25.1