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=ham 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 C326EC432C3 for ; Wed, 27 Nov 2019 21:16:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8BB4F2154A for ; Wed, 27 Nov 2019 21:16:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574889405; bh=nHVmU/oIFzQsYfQS/3JhrMAgd1hf4fvK2RzpONW5VZY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=wvgs+Q5MhoRYCPCci4X0heoR5JyN07+7n6odd9pPAoKvHZhj+f8w0yNnEaVvqHfDE 25DNAOzkAObMmdqkq8WTo1MG/EAKj7SoAJ4yp3dV3aNAfhyXFvmNHDoxOvfl2iIDVL WaIEZHTSN99PmxgtiA7R/08trczH88/63dEPI8t8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733025AbfK0VQo (ORCPT ); Wed, 27 Nov 2019 16:16:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:46226 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732618AbfK0VNn (ORCPT ); Wed, 27 Nov 2019 16:13:43 -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 E1DB0215F1; Wed, 27 Nov 2019 21:13:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574889223; bh=nHVmU/oIFzQsYfQS/3JhrMAgd1hf4fvK2RzpONW5VZY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V5ncSDYf8Nnlo5o6V1aHiTK/BlmKrrjBmPPekQDLKSAwLjeRCLTD1gvXzzyn4jLw4 At1UVw2lCxTpqtffdi0Ra5miXFWVhN/Me3c2Ahl4PmZaaE+dDzCVccIu+mV2YBxdtt 6JJu4Z0Q6J7rnkEs2+/bSiA8bKYFdFJ6QcyZXHO0= 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 5.4 35/66] cpufreq: Add NULL checks to show() and store() methods of cpufreq Date: Wed, 27 Nov 2019 21:32:30 +0100 Message-Id: <20191127202713.995299070@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191127202632.536277063@linuxfoundation.org> References: <20191127202632.536277063@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 @@ -933,6 +933,9 @@ 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); @@ -947,6 +950,9 @@ 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().