From patchwork Tue May 17 07:23:44 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Guozihua (Scott)" X-Patchwork-Id: 12852025 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 6327EC433FE for ; Tue, 17 May 2022 07:25:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236160AbiEQHZS (ORCPT ); Tue, 17 May 2022 03:25:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235896AbiEQHZR (ORCPT ); Tue, 17 May 2022 03:25:17 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 43B6443EDC; Tue, 17 May 2022 00:25:16 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4L2SL26jKtzhZLQ; Tue, 17 May 2022 15:24:26 +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; Tue, 17 May 2022 15:25:14 +0800 From: GUO Zihua To: CC: , , , Subject: [PATCH -next] evm: Refector struct evm_xattr Date: Tue, 17 May 2022 15:23:44 +0800 Message-ID: <20220517072344.23576-1-guozihua@huawei.com> X-Mailer: git-send-email 2.36.0 MIME-Version: 1.0 X-Originating-IP: [10.67.175.31] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) 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 is glued together one flexible array and one fixed length array. The original intention seems to 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 and spars yield the following warning: security/integrity/evm/evm_main.c:852:30: warning: using sizeof on a flexible structure security/integrity/evm/evm_main.c:862:32: warning: using sizeof on a flexible 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. Reference: https://github.com/KSPP/linux/issues/174 Fixes: 6be5cc5246f80 ("evm: add support for different security.evm data types") Signed-off-by: GUO Zihua --- 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 {