From patchwork Mon Aug 30 16:05:05 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 504466 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 2AC70C432BE for ; Mon, 30 Aug 2021 16:05:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 09C6961004 for ; Mon, 30 Aug 2021 16:05:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237726AbhH3QGe (ORCPT ); Mon, 30 Aug 2021 12:06:34 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:65360 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237659AbhH3QGe (ORCPT ); Mon, 30 Aug 2021 12:06:34 -0400 Received: from fsav312.sakura.ne.jp (fsav312.sakura.ne.jp [153.120.85.143]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 17UG571e040414; Tue, 31 Aug 2021 01:05:07 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav312.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav312.sakura.ne.jp); Tue, 31 Aug 2021 01:05:07 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav312.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 17UG56nK040407 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Tue, 31 Aug 2021 01:05:07 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: [PATCH] fbmem: don't allow too huge resolutions To: Daniel Vetter , Geert Uytterhoeven Cc: syzbot , akpm@linux-foundation.org, b.zolnierkie@samsung.com, colin.king@canonical.com, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, masahiroy@kernel.org, syzkaller-bugs@googlegroups.com, 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> From: Tetsuo Handa Message-ID: <535e404d-03bf-8e7a-b296-132a2a98c599@i-love.sakura.ne.jp> Date: Tue, 31 Aug 2021 01:05:05 +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: <339bfb21-8e80-c7d9-46dd-c416f87c50c0@infradead.org> Content-Language: en-US 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. This patch does not use array_size(), for array_size() is allowed to return UINT_MAX on 32bits even if overflow did not happen. We want to detect only overflow here, for individual module will recheck with more strict limits as needed. Link: https://syzkaller.appspot.com/bug?extid=04168c8063cfdde1db5e [1] Reported-by: syzbot Debugged-by: Randy Dunlap Signed-off-by: Tetsuo Handa Tested-by: syzbot Reviewed-by: Geert Uytterhoeven --- drivers/video/fbdev/core/fbmem.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 1c855145711b..9f5075dc2345 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1008,6 +1008,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var) if (var->xres < 8 || var->yres < 8) return -EINVAL; + /* Don't allow u32 * u32 to overflow. */ + if ((u64) var->xres * var->yres > UINT_MAX || + (u64) var->xres_virtual * var->yres_virtual > UINT_MAX) + return -EINVAL; + ret = info->fbops->fb_check_var(var, info); if (ret)