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 9D415C43217 for ; Thu, 1 Dec 2022 19:12:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230162AbiLATMK (ORCPT ); Thu, 1 Dec 2022 14:12:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229962AbiLATMJ (ORCPT ); Thu, 1 Dec 2022 14:12:09 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07353C5E3B; Thu, 1 Dec 2022 11:12:07 -0800 (PST) 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 ams.source.kernel.org (Postfix) with ESMTPS id A6DBEB82008; Thu, 1 Dec 2022 19:12:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19036C433C1; Thu, 1 Dec 2022 19:12:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669921925; bh=faLfLn20VwD7SpEhsVcCsFu680sV7lPRVza931ELf/M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iaivx7/3l5XEFtOnUIq2Fku+PTgJ4+Bl0/M6Yl1yn2H1O6nCNg5lIDyS5to5uYwD3 gULuQyMpYSX2fjkltzqqwx6gHtOFvudGqpjARhsnPp5ulcLjdYrJFAqgxVhHdMwy9E VPS1MvWRYR8Bi/Y+exOe/txwEUw0v6+GogzWk9f7+WYc1n3aglzk0nwt3mKrZl8qje s2IJUngHzxQtY4RaGoBfVIZQsHg4w/FMaetzG9l3tfgoyyRn8OE511rzE2OCnsiFH4 xdP/O6x1Q+C3+Ep4NyV115CokVQ9Llm03OMO2FamRueAZqX9AAu5tlB+LafRhfWbE4 ijOV75CF9mJGw== Date: Thu, 1 Dec 2022 11:12:03 -0800 From: Eric Biggers To: Mimi Zohar Cc: Roberto Sassu , 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 Subject: Re: [PATCH v2 1/2] evm: Alloc evm_digest in evm_verify_hmac() if CONFIG_VMAP_STACK=y Message-ID: References: <20221201100625.916781-1-roberto.sassu@huaweicloud.com> <20221201100625.916781-2-roberto.sassu@huaweicloud.com> <66d9f3dbfddc5d73e73fa0c6152d70ff1739427a.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <66d9f3dbfddc5d73e73fa0c6152d70ff1739427a.camel@linux.ibm.com> Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Thu, Dec 01, 2022 at 02:08:58PM -0500, Mimi Zohar 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 cbounterpart. > > > > > > 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. > > Enabling CONFIG_VMAP_STACK is the culprit, which triggers the BUG_ON > only when CONFIG_DEBUG_SG is enabled as well. > > Refer to commit ba14a194a434 ("fork: Add generic vmalloced stack > support"). I'm asking about where the actual bug is. Where is a scatterlist being created to represent an on-disk buffer... - Eric