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 344F7C433EF for ; Wed, 18 May 2022 05:04:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230061AbiERFED (ORCPT ); Wed, 18 May 2022 01:04:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52330 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230046AbiERFEB (ORCPT ); Wed, 18 May 2022 01:04:01 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E692815A0E; Tue, 17 May 2022 22:04:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1E28C61749; Wed, 18 May 2022 05:04:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02FB8C385A5; Wed, 18 May 2022 05:03:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1652850239; bh=lSzlfK/0P+B4mxaeyy93zDIWo7rAvWr2cqZq2BGe2cM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iPryZ3oC1Rn6JBWJVmSUzTmW+fjDSrinGRBzxM9sETeE0T+IIJsQ3VxRMTfGvQARH d5RBwOBSRuR4AvIko46Toh+sHz199Hj5kmumTywYOrZMH9mHsNTFvRTOG4bX+Waj2/ xaPvazDpcV0fCpuKZ0H2n2lLZXHbYD7ANEPFYBuaanzupW1wVhXlu4ZG1RCW2wqv+6 8wDp7VlGs5YMwL1MnT8Jo2yuO8Qb+lpsbScqQlaGYYyA1SdGG3gQCKx49Umpl9HBE3 Xs0mD7Xxt6n1uE+PTSlpWyWMiq6ECHt0UbtpyZ/2WnjgC/L3APqJIBT0jFiY8/7Br6 WhvoQQ3Pcv0jw== Date: Wed, 18 May 2022 00:13:26 -0500 From: "Gustavo A. R. Silva" To: GUO Zihua Cc: linux-integrity@vger.kernel.org, zohar@linux.ibm.com, dmitry.kasatkin@gmail.com, linux-hardening@vger.kernel.org Subject: Re: [RESEND] evm: Refector struct evm_xattr Message-ID: <20220518051326.GB16144@embeddedor> References: <20220518011439.184809-1-guozihua@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220518011439.184809-1-guozihua@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Wed, May 18, 2022 at 09:14:39AM +0800, GUO Zihua wrote: > 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: The sparse warning has nothing to do with any GCC specification. It's perfectly fine to apply the sizeof operator to a struct-with-flex-array. However, it might be suspicious if the intention is to also get the _dynamic_ size of the flexible array, because in that case the size of the flex array is always zero. See the example below: struct foo { uint8_t len; struct boo data[]; }; sizeof(struct foo) == 1 Also, you sent this patch twice in the last 24 hours. Give the maintainers time to review your patch (usually a couple of weeks) before resending it. > > 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 Regarding the warnings above, please take a look at my response to your other patch (the same applies in this case). :) Thanks -- Gustavo > > 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 { > -- > 2.36.0 >