From patchwork Wed May 18 06:32:32 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Guozihua (Scott)" X-Patchwork-Id: 12853197 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 BEB2BC433FE for ; Wed, 18 May 2022 06:34:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231303AbiERGe0 (ORCPT ); Wed, 18 May 2022 02:34:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231393AbiERGeR (ORCPT ); Wed, 18 May 2022 02:34:17 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 159EAE15DA; Tue, 17 May 2022 23:34:05 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4L337v1RhCz1JBlC; Wed, 18 May 2022 14:32:43 +0800 (CST) Received: from huawei.com (10.67.175.31) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 18 May 2022 14:34:04 +0800 From: GUO Zihua To: CC: , , , Subject: [PATCH v2] evm: Refector struct evm_xattr Date: Wed, 18 May 2022 14:32:32 +0800 Message-ID: <20220518063232.239089-1-guozihua@huawei.com> X-Mailer: git-send-email 2.36.0 MIME-Version: 1.0 X-Originating-IP: [10.67.175.31] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm500024.china.huawei.com (7.185.36.203) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org struct evm_xattr is only used for EVM_XATTR_HMAC type evm digest and glues together one flexible array and one fixed length array. The original intention might be shortening the code as the "data" field would always be a SHA1 digest. This implementation is not complying with GCC's specification about flexible array which requires that flexible should be the last member of a structure and structure of flexible array should not be a sub structure. Fix it by: 1. Remove struct evm_xattr and use struct evm_ima_xattr_data directly. 2. Get array size with struct_size instead of sizeof as suggested by Linus. Reference: https://lore.kernel.org/all/CAHk-=wiGWjxs7EVUpccZEi6esvjpHJdgHQ=vtUeJ5crL62hx9A@mail.gmail.com/ Fixes: 6be5cc5246f80 ("evm: add support for different security.evm data types") Signed-off-by: GUO Zihua --- v2: Change the patch subject to PATCH instead of PATCH -next. Update commit message based on feedback from Gustavo on another patch. --- security/integrity/evm/evm_main.c | 14 ++++++++------ security/integrity/integrity.h | 6 ------ 2 files changed, 8 insertions(+), 12 deletions(-) diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 7d87772f0ce6..f2c4501a287a 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -211,7 +211,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, /* check value type */ switch (xattr_data->type) { case EVM_XATTR_HMAC: - if (xattr_len != sizeof(struct evm_xattr)) { + if (xattr_len != struct_size(*xattr_data, data, + SHA1_DIGEST_SIZE)) { evm_status = INTEGRITY_FAIL; goto out; } @@ -842,24 +843,25 @@ int evm_inode_init_security(struct inode *inode, const struct xattr *lsm_xattr, struct xattr *evm_xattr) { - struct evm_xattr *xattr_data; + struct evm_ima_xattr_data *xattr_data; int rc; if (!(evm_initialized & EVM_INIT_HMAC) || !evm_protected_xattr(lsm_xattr->name)) return 0; - xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); + xattr_data = kzalloc(struct_size(*xattr_data, data, + SHA1_DIGEST_SIZE), GFP_NOFS); if (!xattr_data) return -ENOMEM; - xattr_data->data.type = EVM_XATTR_HMAC; - rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest); + xattr_data->type = EVM_XATTR_HMAC; + rc = evm_init_hmac(inode, lsm_xattr, xattr_data->data); if (rc < 0) goto out; evm_xattr->value = xattr_data; - evm_xattr->value_len = sizeof(*xattr_data); + evm_xattr->value_len = struct_size(*xattr_data, data, SHA1_DIGEST_SIZE); evm_xattr->name = XATTR_EVM_SUFFIX; return 0; out: diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h index 3510e413ea17..91b16d620dd9 100644 --- a/security/integrity/integrity.h +++ b/security/integrity/integrity.h @@ -86,12 +86,6 @@ struct evm_ima_xattr_data { u8 data[]; } __packed; -/* Only used in the EVM HMAC code. */ -struct evm_xattr { - struct evm_ima_xattr_data data; - u8 digest[SHA1_DIGEST_SIZE]; -} __packed; - #define IMA_MAX_DIGEST_SIZE 64 struct ima_digest_data {