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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4F19C38145 for ; Fri, 2 Sep 2022 12:47:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237654AbiIBMrl (ORCPT ); Fri, 2 Sep 2022 08:47:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237581AbiIBMrO (ORCPT ); Fri, 2 Sep 2022 08:47:14 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3857DEB47; Fri, 2 Sep 2022 05:34:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4C5A76212E; Fri, 2 Sep 2022 12:33:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4195BC433D7; Fri, 2 Sep 2022 12:33:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1662122027; bh=Uk4hLiPJocqiO6tbAqBSSCacJn6LjD8UNbJhRkRruFM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=i0LnT3nQ75Q7oN1TwN5bqD7H5GBaODvpf7gaxbU16ZpR03FRi98ao9nqi5oJn+Wfs FquWl5zDzx5jRK/hty3GCuOEmUuRhwIt2woT3/ot1tkQ7BfqfNY5XefmL5KD2S6MLe G0ZegFzFxpNQD24pxsRr/Qb5BEIwls+bFa1XoV9k= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Zheyu Ma , Letu Ren , Helge Deller Subject: [PATCH 5.15 32/73] fbdev: fb_pm2fb: Avoid potential divide by zero error Date: Fri, 2 Sep 2022 14:18:56 +0200 Message-Id: <20220902121405.506473778@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220902121404.435662285@linuxfoundation.org> References: <20220902121404.435662285@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Letu Ren commit 19f953e7435644b81332dd632ba1b2d80b1e37af upstream. In `do_fb_ioctl()` of fbmem.c, if cmd is FBIOPUT_VSCREENINFO, var will be copied from user, then go through `fb_set_var()` and `info->fbops->fb_check_var()` which could may be `pm2fb_check_var()`. Along the path, `var->pixclock` won't be modified. This function checks whether reciprocal of `var->pixclock` is too high. If `var->pixclock` is zero, there will be a divide by zero error. So, it is necessary to check whether denominator is zero to avoid crash. As this bug is found by Syzkaller, logs are listed below. divide error in pm2fb_check_var Call Trace: fb_set_var+0x367/0xeb0 drivers/video/fbdev/core/fbmem.c:1015 do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1110 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1189 Reported-by: Zheyu Ma Signed-off-by: Letu Ren Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman --- drivers/video/fbdev/pm2fb.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/video/fbdev/pm2fb.c +++ b/drivers/video/fbdev/pm2fb.c @@ -617,6 +617,11 @@ static int pm2fb_check_var(struct fb_var return -EINVAL; } + if (!var->pixclock) { + DPRINTK("pixclock is zero\n"); + return -EINVAL; + } + if (PICOS2KHZ(var->pixclock) > PM2_MAX_PIXCLOCK) { DPRINTK("pixclock too high (%ldKHz)\n", PICOS2KHZ(var->pixclock));