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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 00FFEC432C3 for ; Wed, 27 Nov 2019 21:20:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CAFAF217BA for ; Wed, 27 Nov 2019 21:20:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574889652; bh=pB+3gUPuAltXfAtFIuNBs7ZGOUpl7sh6mg06gRg+cOc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=aNJiT9n7MxApadXUJ87pstvnrDKG2cxXUQBvVlZIxVge1az0LEMzV1fc2aNvzlaIz M15Ek+fW+tPMxbhQNSvMQrJpwKpnKIzhd/2Lr0PgdPMLG9X/HUHDQJ0HOslhxqySO9 KW+GcUlk19/rK+yoDbureWgxmThkPBNHQgGvMKSY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732218AbfK0VIS (ORCPT ); Wed, 27 Nov 2019 16:08:18 -0500 Received: from mail.kernel.org ([198.145.29.99]:34738 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732109AbfK0VIS (ORCPT ); Wed, 27 Nov 2019 16:08:18 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 B166021775; Wed, 27 Nov 2019 21:08:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574888897; bh=pB+3gUPuAltXfAtFIuNBs7ZGOUpl7sh6mg06gRg+cOc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UJEMbu1f4dpoi6PuU7EwBionYffUxLMKzaUpCd+/SqlFW23bnPatkNsVTzOhh3f4I xCScgmkRu1FC0/tw4tiDqN4BV+3EaprmOQSCA/LvuNud37d6JT3IFqDMkXTMjmHbuk fItOt08ZMGo7vBKGlOTLE/SAq6wWV4s0bEhaY+Oo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kai Shen , Feilong Lin , Viresh Kumar , "Rafael J. Wysocki" Subject: [PATCH 4.19 286/306] cpufreq: Add NULL checks to show() and store() methods of cpufreq Date: Wed, 27 Nov 2019 21:32:16 +0100 Message-Id: <20191127203135.678264000@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191127203114.766709977@linuxfoundation.org> References: <20191127203114.766709977@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Kai Shen commit e6e8df07268c1f75dd9215536e2ce4587b70f977 upstream. Add NULL checks to show() and store() in cpufreq.c to avoid attempts to invoke a NULL callback. Though some interfaces of cpufreq are set as read-only, users can still get write permission using chmod which can lead to a kernel crash, as follows: chmod +w /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq echo 1 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq This bug was found in linux 4.19. Signed-off-by: Kai Shen Reported-by: Feilong Lin Reviewed-by: Feilong Lin Acked-by: Viresh Kumar [ rjw: Subject & changelog ] Cc: All applicable Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- drivers/cpufreq/cpufreq.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -909,6 +909,9 @@ static ssize_t show(struct kobject *kobj struct freq_attr *fattr = to_attr(attr); ssize_t ret; + if (!fattr->show) + return -EIO; + down_read(&policy->rwsem); ret = fattr->show(policy, buf); up_read(&policy->rwsem); @@ -923,6 +926,9 @@ static ssize_t store(struct kobject *kob struct freq_attr *fattr = to_attr(attr); ssize_t ret = -EINVAL; + if (!fattr->store) + return -EIO; + /* * cpus_read_trylock() is used here to work around a circular lock * dependency problem with respect to the cpufreq_register_driver().