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=-9.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 49B91C4742C for ; Mon, 16 Nov 2020 11:44:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DFE4F22245 for ; Mon, 16 Nov 2020 11:44:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727130AbgKPIwW convert rfc822-to-8bit (ORCPT ); Mon, 16 Nov 2020 03:52:22 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]:2104 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726969AbgKPIwW (ORCPT ); Mon, 16 Nov 2020 03:52:22 -0500 Received: from fraeml702-chm.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4CZN7s3tFrz67DF4; Mon, 16 Nov 2020 16:50:33 +0800 (CST) Received: from fraeml714-chm.china.huawei.com (10.206.15.33) by fraeml702-chm.china.huawei.com (10.206.15.51) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1913.5; Mon, 16 Nov 2020 09:52:19 +0100 Received: from fraeml714-chm.china.huawei.com ([10.206.15.33]) by fraeml714-chm.china.huawei.com ([10.206.15.33]) with mapi id 15.01.1913.007; Mon, 16 Nov 2020 09:52:19 +0100 From: Roberto Sassu To: Christoph Hellwig CC: "zohar@linux.ibm.com" , "linux-integrity@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Silviu Vlasceanu , "stable@vger.kernel.org" , "torvalds@linux-foundation.org" , "viro@zeniv.linux.org.uk" , "linux-fsdevel@vger.kernel.org" Subject: RE: [RESEND][PATCH] ima: Set and clear FMODE_CAN_READ in ima_calc_file_hash() Thread-Topic: [RESEND][PATCH] ima: Set and clear FMODE_CAN_READ in ima_calc_file_hash() Thread-Index: AQHWuZM+vbqfejrqe02000rC0h3xoqnHabyAgAMLzKA= Date: Mon, 16 Nov 2020 08:52:19 +0000 Message-ID: <0fd0fb3360194d909ba48f13220f9302@huawei.com> References: <20201113080132.16591-1-roberto.sassu@huawei.com> <20201114111057.GA16415@infradead.org> In-Reply-To: <20201114111057.GA16415@infradead.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.220.96.108] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org > From: Christoph Hellwig [mailto:hch@infradead.org] > Sent: Saturday, November 14, 2020 12:11 PM > On Fri, Nov 13, 2020 at 09:01:32AM +0100, Roberto Sassu wrote: > > Commit a1f9b1c0439db ("integrity/ima: switch to using __kernel_read") > > replaced the __vfs_read() call in integrity_kernel_read() with > > __kernel_read(), a new helper introduced by commit 61a707c543e2a ("fs: > add > > a __kernel_read helper"). > > > > Since the new helper requires that also the FMODE_CAN_READ flag is set > in > > file->f_mode, this patch saves the original f_mode and sets the flag if the > > the file descriptor has the necessary file operation. Lastly, it restores > > the original f_mode at the end of ima_calc_file_hash(). > > This looks bogus. FMODE_CAN_READ has a pretty clear definition and > you can't just go and read things if it is not set. Also f_mode > manipulations on a life file are racy. FMODE_CAN_READ was not set because f_mode does not have FMODE_READ. In the patch, I check if the former can be set similarly to the way it is done in file_table.c and open.c. Is there a better way to read a file when the file was not opened for reading and a new file descriptor cannot be created? Thanks Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli > > Cc: stable@vger.kernel.org # 5.8.x > > Fixes: a1f9b1c0439db ("integrity/ima: switch to using __kernel_read") > > Signed-off-by: Roberto Sassu > > --- > > security/integrity/ima/ima_crypto.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/security/integrity/ima/ima_crypto.c > b/security/integrity/ima/ima_crypto.c > > index 21989fa0c107..22ed86a0c964 100644 > > --- a/security/integrity/ima/ima_crypto.c > > +++ b/security/integrity/ima/ima_crypto.c > > @@ -537,6 +537,7 @@ int ima_calc_file_hash(struct file *file, struct > ima_digest_data *hash) > > loff_t i_size; > > int rc; > > struct file *f = file; > > + fmode_t saved_mode; > > bool new_file_instance = false, modified_mode = false; > > > > /* > > @@ -550,7 +551,7 @@ int ima_calc_file_hash(struct file *file, struct > ima_digest_data *hash) > > } > > > > /* Open a new file instance in O_RDONLY if we cannot read */ > > - if (!(file->f_mode & FMODE_READ)) { > > + if (!(file->f_mode & FMODE_READ) || !(file->f_mode & > FMODE_CAN_READ)) { > > int flags = file->f_flags & ~(O_WRONLY | O_APPEND | > > O_TRUNC | O_CREAT | O_NOCTTY | > O_EXCL); > > flags |= O_RDONLY; > > @@ -562,7 +563,10 @@ int ima_calc_file_hash(struct file *file, struct > ima_digest_data *hash) > > */ > > pr_info_ratelimited("Unable to reopen file for > reading.\n"); > > f = file; > > + saved_mode = f->f_mode; > > f->f_mode |= FMODE_READ; > > + if (likely(file->f_op->read || file->f_op->read_iter)) > > + f->f_mode |= FMODE_CAN_READ; > > modified_mode = true; > > } else { > > new_file_instance = true; > > @@ -582,7 +586,7 @@ int ima_calc_file_hash(struct file *file, struct > ima_digest_data *hash) > > if (new_file_instance) > > fput(f); > > else if (modified_mode) > > - f->f_mode &= ~FMODE_READ; > > + f->f_mode = saved_mode; > > return rc; > > } > > > > -- > > 2.27.GIT > > > ---end quoted text---