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 3A2F5C6FD18 for ; Fri, 31 Mar 2023 12:21:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232347AbjCaMVQ (ORCPT ); Fri, 31 Mar 2023 08:21:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230331AbjCaMU7 (ORCPT ); Fri, 31 Mar 2023 08:20:59 -0400 Received: from frasgout11.his.huawei.com (frasgout11.his.huawei.com [14.137.139.23]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7584B1F788; Fri, 31 Mar 2023 05:20:13 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.18.147.228]) by frasgout11.his.huawei.com (SkyGuard) with ESMTP id 4Pnzct19HTz9v7gV; Fri, 31 Mar 2023 20:10:06 +0800 (CST) Received: from roberto-ThinkStation-P620 (unknown [10.204.63.22]) by APP2 (Coremail) with SMTP id GxC2BwAn+V+lzyZkRqPiAQ--.4795S2; Fri, 31 Mar 2023 13:18:56 +0100 (CET) Message-ID: Subject: Re: [PATCH v9 3/4] evm: Align evm_inode_init_security() definition with LSM infrastructure From: Roberto Sassu To: Paul Moore Cc: zohar@linux.ibm.com, dmitry.kasatkin@gmail.com, jmorris@namei.org, serge@hallyn.com, stephen.smalley.work@gmail.com, eparis@parisplace.org, casey@schaufler-ca.com, reiserfs-devel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, bpf@vger.kernel.org, kpsingh@kernel.org, keescook@chromium.org, nicolas.bouchinet@clip-os.org, Roberto Sassu Date: Fri, 31 Mar 2023 14:18:42 +0200 In-Reply-To: References: <20230329130415.2312521-1-roberto.sassu@huaweicloud.com> <20230329130415.2312521-4-roberto.sassu@huaweicloud.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID: GxC2BwAn+V+lzyZkRqPiAQ--.4795S2 X-Coremail-Antispam: 1UD129KBjvJXoW3GF4rurWrtr1Uuw1kurykXwb_yoWxGF4DpF WDta1Uurs8JFy5WryFvF4Uu3WS93yrGr4jqr93G34jyF1Dtrn7try0yr15uFyrWrW8Gr1v qw42vF4furn8t3DanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkjb4IE77IF4wAFF20E14v26ryj6rWUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Jr0_JF4l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVW8JVWxJwA2z4x0Y4vEx4A2jsIEc7CjxV AFwI0_Gr0_Gr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40E x7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x 0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1l42xK82IYc2Ij 64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x 8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r4a6rW5MIIYrxkI7VAKI48JMIIF0xvE 2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42 xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIE c7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07UZ18PUUUUU= X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAgANBF1jj4dr6AABs- X-CFilter-Loop: Reflected Precedence: bulk List-ID: On Fri, 2023-03-31 at 09:32 +0200, Roberto Sassu wrote: > On Thu, 2023-03-30 at 18:55 -0400, Paul Moore wrote: > > On Wed, Mar 29, 2023 at 9:05 AM Roberto Sassu > > wrote: > > > From: Roberto Sassu > > > > > > Change the evm_inode_init_security() definition to align with the LSM > > > infrastructure. Keep the existing behavior of including in the HMAC > > > calculation only the first xattr provided by LSMs. > > > > > > Changing the evm_inode_init_security() definition requires passing the > > > xattr array allocated by security_inode_init_security(), and the number of > > > xattrs filled by previously invoked LSMs. > > > > > > Use the newly introduced lsm_find_xattr_slot() to position EVM correctly in > > > the xattrs array, like a regular LSM, and to increment the number of filled > > > slots. For now, the LSM infrastructure allocates enough xattrs slots to > > > store the EVM xattr, without using the reservation mechanism. > > > > > > Finally, make evm_inode_init_security() return value compatible with the > > > inode_init_security hook conventions, i.e. return -EOPNOTSUPP if it is not > > > setting an xattr. > > > > > > EVM is a bit tricky, because xattrs is both an input and an output. If it > > > was just output, EVM should have returned zero if xattrs is NULL. But, > > > since xattrs is also input, EVM is unable to do its calculations, so return > > > -EOPNOTSUPP and handle this error in security_inode_init_security(). > > > > I don't quite understand why EVM would return EOPNOTSUPP if it is > > enabled but there are not xattrs to measure. It seems like EVM should > > return success/0 in the no-xattr case; there were no xattrs to > > measure, so it succeeded in measuring nothing. Am I missing > > something? > > From a very quick look at what other LSMs do, it seems that they return > zero even if they are not initialized. > > So, it makes sense to return zero also here. Oh, actually there was a reason to do that. If an LSM does not wish to provide an xattr, it should return -EOPNOTSUPP. As we are not checking this convention anymore, it is probably fine to return zero. I already made the change, will send the new version shortly. Thanks Roberto > Thanks > > Roberto > > > > Signed-off-by: Roberto Sassu > > > --- > > > include/linux/evm.h | 14 ++++++++------ > > > security/integrity/evm/evm_main.c | 18 +++++++++++------- > > > security/security.c | 6 +++--- > > > 3 files changed, 22 insertions(+), 16 deletions(-) > > > > > > diff --git a/include/linux/evm.h b/include/linux/evm.h > > > index 7dc1ee74169..3c0e8591b69 100644 > > > --- a/include/linux/evm.h > > > +++ b/include/linux/evm.h > > > @@ -56,9 +56,10 @@ static inline void evm_inode_post_set_acl(struct dentry *dentry, > > > { > > > return evm_inode_post_setxattr(dentry, acl_name, NULL, 0); > > > } > > > -extern int evm_inode_init_security(struct inode *inode, > > > - const struct xattr *xattr_array, > > > - struct xattr *evm); > > > +extern int evm_inode_init_security(struct inode *inode, struct inode *dir, > > > + const struct qstr *qstr, > > > + struct xattr *xattrs, > > > + int *num_filled_xattrs); > > > extern bool evm_revalidate_status(const char *xattr_name); > > > extern int evm_protected_xattr_if_enabled(const char *req_xattr_name); > > > extern int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer, > > > @@ -157,9 +158,10 @@ static inline void evm_inode_post_set_acl(struct dentry *dentry, > > > return; > > > } > > > > > > -static inline int evm_inode_init_security(struct inode *inode, > > > - const struct xattr *xattr_array, > > > - struct xattr *evm) > > > +static inline int evm_inode_init_security(struct inode *inode, struct inode *dir, > > > + const struct qstr *qstr, > > > + struct xattr *xattrs, > > > + int *num_filled_xattrs) > > > { > > > return 0; > > > } > > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > > > index cf24c525558..9e75759150c 100644 > > > --- a/security/integrity/evm/evm_main.c > > > +++ b/security/integrity/evm/evm_main.c > > > @@ -21,6 +21,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > > > > #include > > > #include > > > @@ -864,23 +865,26 @@ void evm_inode_post_setattr(struct dentry *dentry, int ia_valid) > > > /* > > > * evm_inode_init_security - initializes security.evm HMAC value > > > */ > > > -int evm_inode_init_security(struct inode *inode, > > > - const struct xattr *lsm_xattr, > > > - struct xattr *evm_xattr) > > > +int evm_inode_init_security(struct inode *inode, struct inode *dir, > > > + const struct qstr *qstr, struct xattr *xattrs, > > > + int *num_filled_xattrs) > > > { > > > struct evm_xattr *xattr_data; > > > + struct xattr *evm_xattr; > > > int rc; > > > > > > - if (!(evm_initialized & EVM_INIT_HMAC) || > > > - !evm_protected_xattr(lsm_xattr->name)) > > > - return 0; > > > + if (!(evm_initialized & EVM_INIT_HMAC) || !xattrs || > > > + !evm_protected_xattr(xattrs->name)) > > > + return -EOPNOTSUPP; > > > + > > > + evm_xattr = lsm_find_xattr_slot(xattrs, num_filled_xattrs); > > > > > > xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); > > > if (!xattr_data) > > > return -ENOMEM; > > > > > > xattr_data->data.type = EVM_XATTR_HMAC; > > > - rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest); > > > + rc = evm_init_hmac(inode, xattrs, xattr_data->digest); > > > if (rc < 0) > > > goto out; > > > > > > diff --git a/security/security.c b/security/security.c > > > index be33d643a81..22ab4fb7ebf 100644 > > > --- a/security/security.c > > > +++ b/security/security.c > > > @@ -1674,9 +1674,9 @@ int security_inode_init_security(struct inode *inode, struct inode *dir, > > > if (!num_filled_xattrs) > > > goto out; > > > > > > - ret = evm_inode_init_security(inode, new_xattrs, > > > - new_xattrs + num_filled_xattrs); > > > - if (ret) > > > + ret = evm_inode_init_security(inode, dir, qstr, new_xattrs, > > > + &num_filled_xattrs); > > > + if (ret && ret != -EOPNOTSUPP) > > > goto out; > > > ret = initxattrs(inode, new_xattrs, fs_data); > > > out: > > > -- > > > 2.25.1 > > >