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 BAEB5C4332F for ; Thu, 8 Dec 2022 08:33:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229888AbiLHIdJ (ORCPT ); Thu, 8 Dec 2022 03:33:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229589AbiLHIdG (ORCPT ); Thu, 8 Dec 2022 03:33:06 -0500 Received: from frasgout11.his.huawei.com (frasgout11.his.huawei.com [14.137.139.23]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1B6CB27161; Thu, 8 Dec 2022 00:33:03 -0800 (PST) Received: from mail02.huawei.com (unknown [172.18.147.228]) by frasgout11.his.huawei.com (SkyGuard) with ESMTP id 4NSS0G66C5z9xHw7; Thu, 8 Dec 2022 16:25:50 +0800 (CST) Received: from roberto-ThinkStation-P620 (unknown [10.204.63.22]) by APP1 (Coremail) with SMTP id LxC2BwBHM3AjoZFjn3rMAA--.59558S2; Thu, 08 Dec 2022 09:32:43 +0100 (CET) Message-ID: <971b28db46dfb4437080b18ba042b290abaf960f.camel@huaweicloud.com> Subject: Re: [PATCH v2 1/2] evm: Alloc evm_digest in evm_verify_hmac() if CONFIG_VMAP_STACK=y From: Roberto Sassu To: Mimi Zohar , Eric Biggers Cc: dmitry.kasatkin@gmail.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Roberto Sassu , stable@vger.kernel.org Date: Thu, 08 Dec 2022 09:32:33 +0100 In-Reply-To: References: <20221201100625.916781-1-roberto.sassu@huaweicloud.com> <20221201100625.916781-2-roberto.sassu@huaweicloud.com> <5813b77edf8f8c6c68da8343b7898f2a5c831077.camel@huaweicloud.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-CM-TRANSID: LxC2BwBHM3AjoZFjn3rMAA--.59558S2 X-Coremail-Antispam: 1UD129KBjvJXoWxGFy8Ww4DuF1UGF15ZryUGFg_yoW7JF4kpa 1kK3W8Kr45Jr1fCF12v3WYy3Z5KrW8tryUWrs8Jw1YyFyqqrnFyw1Iyr1UWryFgry8GF12 qFW8trnxCr15Aa7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkjb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Jr0_JF4l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVW8JVWxJwA2z4x0Y4vEx4A2jsIEc7CjxV AFwI0_Gr0_Gr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40E x7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x 0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1l42xK82IYc2Ij 64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x 8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43MIIYrxkI7VAKI48JMIIF0xvE 2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42 xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIE c7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07UWE__UUUUU= X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAQAABF1jj4ZryQADsT X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2022-12-07 at 20:26 -0500, Mimi Zohar wrote: > On Mon, 2022-12-05 at 09:22 +0100, Roberto Sassu wrote: > > On Fri, 2022-12-02 at 10:49 -0800, Eric Biggers wrote: > > > On Fri, Dec 02, 2022 at 08:58:21AM +0100, Roberto Sassu wrote: > > > > On Thu, 2022-12-01 at 10:53 -0800, Eric Biggers wrote: > > > > > On Thu, Dec 01, 2022 at 11:06:24AM +0100, Roberto Sassu wrote: > > > > > > From: Roberto Sassu > > > > > > > > > > > > Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear > > > > > > mapping") checks that both the signature and the digest reside in the > > > > > > linear mapping area. > > > > > > > > > > > > However, more recently commit ba14a194a434c ("fork: Add generic vmalloced > > > > > > stack support"), made it possible to move the stack in the vmalloc area, > > > > > > which is not contiguous, and thus not suitable for sg_set_buf() which needs > > > > > > adjacent pages. > > > > > > > > > > > > Fix this by checking if CONFIG_VMAP_STACK is enabled. If yes, allocate an > > > > > > evm_digest structure, and use that instead of the in-stack counterpart. > > > > > > > > > > > > Cc: stable@vger.kernel.org # 4.9.x > > > > > > Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support") > > > > > > Signed-off-by: Roberto Sassu > > > > > > --- > > > > > > security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- > > > > > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > > > > > > > > > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c > > > > > > index 23d484e05e6f..7f76d6103f2e 100644 > > > > > > --- a/security/integrity/evm/evm_main.c > > > > > > +++ b/security/integrity/evm/evm_main.c > > > > > > @@ -174,6 +174,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > > > struct signature_v2_hdr *hdr; > > > > > > enum integrity_status evm_status = INTEGRITY_PASS; > > > > > > struct evm_digest digest; > > > > > > + struct evm_digest *digest_ptr = &digest; > > > > > > struct inode *inode; > > > > > > int rc, xattr_len, evm_immutable = 0; > > > > > > > > > > > > @@ -231,14 +232,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > > > } > > > > > > > > > > > > hdr = (struct signature_v2_hdr *)xattr_data; > > > > > > - digest.hdr.algo = hdr->hash_algo; > > > > > > + > > > > > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > > > > > + digest_ptr = kmalloc(sizeof(*digest_ptr), GFP_NOFS); > > > > > > + if (!digest_ptr) { > > > > > > + rc = -ENOMEM; > > > > > > + break; > > > > > > + } > > > > > > + } > > > > > > + > > > > > > + digest_ptr->hdr.algo = hdr->hash_algo; > > > > > > + > > > > > > rc = evm_calc_hash(dentry, xattr_name, xattr_value, > > > > > > - xattr_value_len, xattr_data->type, &digest); > > > > > > + xattr_value_len, xattr_data->type, > > > > > > + digest_ptr); > > > > > > if (rc) > > > > > > break; > > > > > > rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, > > > > > > (const char *)xattr_data, xattr_len, > > > > > > - digest.digest, digest.hdr.length); > > > > > > + digest_ptr->digest, > > > > > > + digest_ptr->hdr.length); > > > > > > if (!rc) { > > > > > > inode = d_backing_inode(dentry); > > > > > > > > > > > > @@ -268,8 +281,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, > > > > > > else > > > > > > evm_status = INTEGRITY_FAIL; > > > > > > } > > > > > > - pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, > > > > > > - digest.digest); > > > > > > + pr_debug("digest: (%d) [%*phN]\n", digest_ptr->hdr.length, > > > > > > + digest_ptr->hdr.length, digest_ptr->digest); > > > > > > + > > > > > > + if (digest_ptr && digest_ptr != &digest) > > > > > > + kfree(digest_ptr); > > > > > > > > > > What is the actual problem here? Where is a scatterlist being created from this > > > > > buffer? AFAICS it never happens. > > > > > > > > Hi Eric > > > > > > > > it is in public_key_verify_signature(), called by asymmetric_verify() > > > > and integrity_digsig_verify(). > > > > > > > > > > Hmm, that's several steps down the stack then. And not something I had > > > expected. > > > > > > Perhaps this should be fixed in public_key_verify_signature() instead? It > > > already does a kmalloc(), so that allocation size just could be made a bit > > > larger to get space for a temporary copy of 's' and 'digest'. > > > > Mimi asked to fix it in both IMA and EVM. > > At the time I thought the problem was limited to > integrity_digsig_verify() and just to the digest. > > I'll leave it up to you and Eric to decide what is the preferable > solution. Ok, yes. I think Eric's suggestion of making a copy in public_key_verify_signature() is better. Will do it. > > > Or at the very least, struct public_key_signature should have a *very* clear > > > comment saying that the 's' and 'digest' fields must be located in physically > > > contiguous memory... > > > > That I could add as an additional patch. > > Thanks, the new patch containing the comment looks fine. Thanks, not sure if I need to keep it with the new patch (probably not). Roberto