From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Date: Fri, 20 Mar 2020 00:07:55 +0000 Subject: Re: [PATCH v5 2/2] KEYS: Avoid false positive ENOMEM error on key read Message-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit List-Id: References: <20200318221457.1330-1-longman@redhat.com> <20200318221457.1330-3-longman@redhat.com> <20200319194650.GA24804@linux.intel.com> In-Reply-To: <20200319194650.GA24804@linux.intel.com> To: Jarkko Sakkinen Cc: David Howells , James Morris , "Serge E. Hallyn" , Mimi Zohar , "David S. Miller" , Jakub Kicinski , keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, netdev@vger.kernel.org, linux-afs@lists.infradead.org, Sumit Garg , Jerry Snitselaar , Roberto Sassu , Eric Biggers , Chris von Recklinghausen On 3/19/20 3:46 PM, Jarkko Sakkinen wrote: > On Wed, Mar 18, 2020 at 06:14:57PM -0400, Waiman Long wrote: >> + * It is possible, though unlikely, that the key >> + * changes in between the up_read->down_read period. >> + * If the key becomes longer, we will have to >> + * allocate a larger buffer and redo the key read >> + * again. >> + */ >> + if (!tmpbuf || unlikely(ret > tmpbuflen)) { > Shouldn't you check that tmpbuflen stays below buflen (why else > you had made copy of buflen otherwise)? The check above this thunk: if ((ret > 0) && (ret <= buflen)) { will make sure that ret will not be larger than buflen. So tmpbuflen will never be bigger than buflen. Cheers, Longman 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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 43535C4332B for ; Fri, 20 Mar 2020 00:08:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0132E20740 for ; Fri, 20 Mar 2020 00:08:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UEvzJ4Nb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727447AbgCTAIG (ORCPT ); Thu, 19 Mar 2020 20:08:06 -0400 Received: from us-smtp-delivery-74.mimecast.com ([63.128.21.74]:57090 "EHLO us-smtp-delivery-74.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727256AbgCTAIE (ORCPT ); Thu, 19 Mar 2020 20:08:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584662883; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Anb5LRo8xpBF1QOjWwn5JazocJjB3iK3v4+s87FrK8A=; b=UEvzJ4NbUVFJ0b37HCB8L+FhTkbAmEeDz6h72T+m4muyPzPbAWdTcAOh8U5gdLHIUQ/0hX /n3pX5Xv6LC0N3lA8547MbzO/cWa3Pi7ycGXaJKuxk9cgVKw/sFwxFXrFedzabgFGAcZVK t+UH3212IQiKDLOt0CB9C0AcAaSzEzM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-100-f_JiBXiuMQ2zkpAPZ_nSSw-1; Thu, 19 Mar 2020 20:08:01 -0400 X-MC-Unique: f_JiBXiuMQ2zkpAPZ_nSSw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DC5D4107ACC7; Fri, 20 Mar 2020 00:07:58 +0000 (UTC) Received: from llong.remote.csb (ovpn-113-139.rdu2.redhat.com [10.10.113.139]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8BC6719C58; Fri, 20 Mar 2020 00:07:55 +0000 (UTC) Subject: Re: [PATCH v5 2/2] KEYS: Avoid false positive ENOMEM error on key read To: Jarkko Sakkinen Cc: David Howells , James Morris , "Serge E. Hallyn" , Mimi Zohar , "David S. Miller" , Jakub Kicinski , keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, netdev@vger.kernel.org, linux-afs@lists.infradead.org, Sumit Garg , Jerry Snitselaar , Roberto Sassu , Eric Biggers , Chris von Recklinghausen References: <20200318221457.1330-1-longman@redhat.com> <20200318221457.1330-3-longman@redhat.com> <20200319194650.GA24804@linux.intel.com> From: Waiman Long Organization: Red Hat Message-ID: Date: Thu, 19 Mar 2020 20:07:55 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20200319194650.GA24804@linux.intel.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/19/20 3:46 PM, Jarkko Sakkinen wrote: > On Wed, Mar 18, 2020 at 06:14:57PM -0400, Waiman Long wrote: >> + * It is possible, though unlikely, that the key >> + * changes in between the up_read->down_read period. >> + * If the key becomes longer, we will have to >> + * allocate a larger buffer and redo the key read >> + * again. >> + */ >> + if (!tmpbuf || unlikely(ret > tmpbuflen)) { > Shouldn't you check that tmpbuflen stays below buflen (why else > you had made copy of buflen otherwise)? The check above this thunk: if ((ret > 0) && (ret <= buflen)) { will make sure that ret will not be larger than buflen. So tmpbuflen will never be bigger than buflen. Cheers, Longman