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 4FFB8C46467 for ; Tue, 29 Nov 2022 14:34:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235684AbiK2OeP (ORCPT ); Tue, 29 Nov 2022 09:34:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235718AbiK2Od4 (ORCPT ); Tue, 29 Nov 2022 09:33:56 -0500 Received: from frasgout11.his.huawei.com (frasgout11.his.huawei.com [14.137.139.23]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1FF96490B3; Tue, 29 Nov 2022 06:33:51 -0800 (PST) Received: from mail02.huawei.com (unknown [172.18.147.227]) by frasgout11.his.huawei.com (SkyGuard) with ESMTP id 4NM4Qv56pbz9v7NK; Tue, 29 Nov 2022 22:26:47 +0800 (CST) Received: from roberto-ThinkStation-P620 (unknown [10.204.63.22]) by APP1 (Coremail) with SMTP id LxC2BwB3Y3AkGIZjHy6nAA--.40286S2; Tue, 29 Nov 2022 15:33:21 +0100 (CET) Message-ID: Subject: Re: [PATCH v5] evm: Correct inode_init_security hooks behaviors From: Roberto Sassu To: Nicolas Bouchinet Cc: Mimi Zohar , linux-integrity@vger.kernel.org, Roberto Sassu , philippe.trebuchet@ssi.gouv.fr, dmitry.kasatkin@gmail.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, casey@schaufler-ca.com, davem@davemloft.net, lucien.xin@gmail.com, vgoyal@redhat.com, omosnace@redhat.com, mortonm@chromium.org, nicolas.bouchinet@ssi.gouv.fr, mic@digikod.net, cgzones@googlemail.com, linux-security-module@vger.kernel.org, kpsingh@kernel.org, revest@chromium.org, jackmanb@chromium.org, bpf@vger.kernel.org Date: Tue, 29 Nov 2022 15:33:05 +0100 In-Reply-To: References: <086b6d26895b84ad4086ac9f191ede6f705f9b6b.camel@linux.ibm.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: LxC2BwB3Y3AkGIZjHy6nAA--.40286S2 X-Coremail-Antispam: 1UD129KBjvJXoWxXryUAw43AF4rJw48CF4Uurg_yoW5Kr18pF W5t3W2kF4DtF18ArWaqw4UZw4xKrWSgrWDWrnrGryUAF98Kr1xJrWIvFWY9Fyfur48GF1q vF17Ja47Zrn8A3DanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkjb4IE77IF4wAFF20E14v26ryj6rWUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Jr0_JF4l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVW8JVWxJwA2z4x0Y4vEx4A2jsIEc7CjxV AFwI0_Gr0_Gr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40E x7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x 0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1l42xK82IYc2Ij 64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x 8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r4a6rW5MIIYrxkI7VAKI48JMIIF0xvE 2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42 xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIE c7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07UZ18PUUUUU= X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAQALBF1jj4YIbgABse X-CFilter-Loop: Reflected Precedence: bulk List-ID: On Tue, 2022-11-29 at 15:31 +0100, Nicolas Bouchinet wrote: > Hi Roberto, > > On Tue, Nov 29, 2022 at 02:10:06PM +0100, Roberto Sassu wrote: > > On Tue, 2022-11-29 at 13:58 +0100, Nicolas Bouchinet wrote: > > > Hi Mimi, > > > > > > On Tue, Nov 29, 2022 at 06:28:09AM -0500, Mimi Zohar wrote: > > > > On Fri, 2022-11-25 at 16:57 +0100, Nicolas Bouchinet wrote: > > > > > From: Nicolas Bouchinet > > > > > > > > > > Fixes a NULL pointer dereference occurring in the > > > > > `evm_protected_xattr_common` function of the EVM LSM. The bug is > > > > > triggered if a `inode_init_security` hook returns 0 without initializing > > > > > the given `struct xattr` fields (which is the case of BPF) and if no > > > > > other LSM overrides thoses fields after. This also leads to memory > > > > > leaks. > > > > > > > > > > The `call_int_hook_xattr` macro has been inlined into the > > > > > `security_inode_init_security` hook in order to check hooks return > > > > > values and skip ones who doesn't init `xattrs`. > > > > > > > > > > Modify `evm_init_hmac` function to init the EVM hmac using every > > > > > entry of the given xattr array. > > > > > > > > > > The `MAX_LSM_EVM_XATTR` value is now based on the security modules > > > > > compiled in, which gives room for SMACK, SELinux, Apparmor, BPF and > > > > > IMA/EVM security attributes. > > > > > > > > > > Changes the default return value of the `inode_init_security` hook > > > > > definition to `-EOPNOTSUPP`. > > > > > > > > > > Changes the hook documentation to match the behavior of the LSMs using > > > > > it (only xattr->value is initialised with kmalloc and thus is the only > > > > > one that should be kfreed by the caller). > > > > > > > > > > Cc: roberto.sassu@huaweicloud.com > > > > > Signed-off-by: Nicolas Bouchinet > > > > > > > > What is the relationship between this patch and Roberto's patch set? > > > > Roberto, if there is an overlap, then at minimum there should be a > > > > Reported-by tag indicating that your patch set addresses a bug reported > > > > by Nicolas. > > > > > > This patch fixes the EVM NULL pointer dereference I have reported, and additionally > > > improves the stackability of this LSM hook. This latter improvement was originally > > > addressed by Roberto's patchset, and thus I see no problem for my fix to be merged > > > within his patchset. > > > > + if (!num_filled_xattrs) > > goto out; > > > > - evm_xattr = lsm_xattr + 1; > > - ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr); > > + ret = evm_inode_init_security(inode, new_xattrs, > > + new_xattrs + num_filled_xattrs); > > > > This part of patch 4 should be enough to fix the issue, until EVM is > > outside the LSM infrastructure. > > > > It prevents EVM from being called if there are no xattrs filled (the > > panic occurred due to xattr->name being NULL). > > > > Then, this part of patch 6: > > > > + for (xattr = xattrs; xattr->value != NULL; xattr++) { > > + if (evm_protected_xattr(xattr->name)) > > + evm_protected_xattrs = true; > > + } > > + > > + /* EVM xattr not needed. */ > > + if (!evm_protected_xattrs) > > + return -EOPNOTSUPP; > > > > should be sufficient for when EVM is managed by the LSM infrastructure. > > > > security_check_compact_filled_xattrs() ensures that if xattr->value is > > not NULL, xattr->name is not NULL too. > > > I think a Reported-by tag should enougth then ! Perfect, will do. Thanks for reporting the issue. Roberto > > Roberto > > > > > > -- > > > > thanks, > > > > > > > > Mimi > > > > > > > > > > Thanks for your time, > > > > > > Nicolas Bouchinet > > Thanks ! > Nicolas Bouchinet