From patchwork Wed Nov 23 15:47:10 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 13053898 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 61422C4332F for ; Wed, 23 Nov 2022 15:49:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238943AbiKWPtJ (ORCPT ); Wed, 23 Nov 2022 10:49:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38212 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238676AbiKWPsr (ORCPT ); Wed, 23 Nov 2022 10:48:47 -0500 Received: from frasgout11.his.huawei.com (frasgout11.his.huawei.com [14.137.139.23]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 936E6C4B43; Wed, 23 Nov 2022 07:48:44 -0800 (PST) Received: from mail02.huawei.com (unknown [172.18.147.227]) by frasgout11.his.huawei.com (SkyGuard) with ESMTP id 4NHQNF1FQDz9xHvP; Wed, 23 Nov 2022 23:41:49 +0800 (CST) Received: from huaweicloud.com (unknown [10.204.63.22]) by APP1 (Coremail) with SMTP id LxC2BwD34W6OQH5jUE+LAA--.33660S6; Wed, 23 Nov 2022 16:48:16 +0100 (CET) From: Roberto Sassu To: mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com, zohar@linux.ibm.com, dmitry.kasatkin@gmail.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, stephen.smalley.work@gmail.com, eparis@parisplace.org, casey@schaufler-ca.com Cc: ocfs2-devel@oss.oracle.com, reiserfs-devel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, linux-kernel@vger.kernel.org, keescook@chromium.org, nicolas.bouchinet@clip-os.org, Roberto Sassu Subject: [PATCH v6 4/6] security: Allow all LSMs to provide xattrs for inode_init_security hook Date: Wed, 23 Nov 2022 16:47:10 +0100 Message-Id: <20221123154712.752074-5-roberto.sassu@huaweicloud.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20221123154712.752074-1-roberto.sassu@huaweicloud.com> References: <20221123154712.752074-1-roberto.sassu@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: LxC2BwD34W6OQH5jUE+LAA--.33660S6 X-Coremail-Antispam: 1UD129KBjvAXoW3Kr1DWw4kCrykJw4fJw1xAFb_yoW8XryxKo WxJwsrArW0gF17GrW5u3Z7JFZruayrWr4fAr1Fvr45A3ZIq34UCw1fXay8XFy3WryrKF48 t34Iya40qrWqqF95n29KB7ZKAUJUUUUU529EdanIXcx71UUUUU7v73VFW2AGmfu7bjvjm3 AaLaJ3UjIYCTnIWjp_UUUYu7kC6x804xWl14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK 8VAvwI8IcIk0rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF 0E3s1l82xGYIkIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vE j48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Jr0_JF4l84ACjcxK6xIIjxv20xvEc7CjxV AFwI0_Cr0_Gr1UM28EF7xvwVC2z280aVAFwI0_Gr0_Cr1l84ACjcxK6I8E87Iv6xkF7I0E 14v26r4UJVWxJr1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrV C2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE 7xkEbVWUJVW8JwACjcxG0xvY0x0EwIxGrwACI402YVCY1x02628vn2kIc2xKxwCF04k20x vY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I 3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_GFv_WrylIxkGc2Ij64vIr41lIx AIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UMIIF 0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVW8JVWxJwCI42IY6I8E87 Iv6xkF7I0E14v26r4UJVWxJrUvcSsGvfC2KfnxnUUI43ZEXa7IU13l1DUUUUU== X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAgAFBF1jj4HMTwABsx X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org From: Roberto Sassu Currently, security_inode_init_security() supports only one LSM providing an xattr and EVM calculating the HMAC on that xattr, plus other inode metadata. Allow all LSMs to provide one or multiple xattrs, by extending the security blob reservation mechanism. Introduce the new lbs_xattr field of the lsm_blob_sizes structure, so that each LSM can specify how many xattrs it needs, and the LSM infrastructure knows how many xattr slots it should allocate. Dynamically allocate the xattrs array to be populated by LSMs with the inode_init_security hook, and pass it to the latter instead of the name/value/len triple. Update the documentation accordingly, and fix the description of the xattr name, as it is not allocated anymore. Since the LSM infrastructure, at initialization time, updates the number of the requested xattrs provided by each LSM with a corresponding offset in the security blob (in this case the xattr array), it makes straightforward for an LSM to access the right position in the xattr array. There is still the issue that an LSM might not fill the xattr, even if it requests it (legitimate case, for example it might have been loaded but not initialized with a policy). Since users of the xattr array (e.g. the initxattrs() callbacks) detect the end of the xattr array by checking if the xattr name is NULL, not filling an xattr would cause those users to stop scanning xattrs prematurely. Solve that issue by introducing security_check_compact_filled_xattrs(), which does a basic check of the xattr array (if the xattr name is filled, the xattr value should be too, and viceversa), and compacts the xattr array by removing the holes. An alternative solution would be to let users of the xattr array know the number of elements of that array, so that they don't have to check the termination. However, this seems more invasive, compared to a simple move of few array elements. security_check_compact_filled_xattrs() also determines how many xattrs in the xattr array have been filled. If there is none, skip evm_inode_init_security() and initxattrs(). Skipping the former also avoids EVM to crash the kernel, as it is expecting a filled xattr. Finally, adapt both SELinux and Smack to use the new definition of the inode_init_security hook, and to correctly fill the designated slots in the xattr array. For Smack, reserve space for the other defined xattrs although they are not set yet in smack_inode_init_security(). Signed-off-by: Roberto Sassu --- include/linux/lsm_hook_defs.h | 3 +- include/linux/lsm_hooks.h | 17 ++++-- security/security.c | 103 +++++++++++++++++++++++++++++----- security/selinux/hooks.c | 19 ++++--- security/smack/smack_lsm.c | 26 +++++---- 5 files changed, 127 insertions(+), 41 deletions(-) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index ec119da1d89b..be344d0211f8 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -112,8 +112,7 @@ LSM_HOOK(int, 0, path_notify, const struct path *path, u64 mask, LSM_HOOK(int, 0, inode_alloc_security, struct inode *inode) LSM_HOOK(void, LSM_RET_VOID, inode_free_security, struct inode *inode) LSM_HOOK(int, 0, inode_init_security, struct inode *inode, - struct inode *dir, const struct qstr *qstr, const char **name, - void **value, size_t *len) + struct inode *dir, const struct qstr *qstr, struct xattr *xattrs) LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode, const struct qstr *name, const struct inode *context_inode) LSM_HOOK(int, 0, inode_create, struct inode *dir, struct dentry *dentry, diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 4ec80b96c22e..ba1655370643 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -229,18 +229,22 @@ * This hook is called by the fs code as part of the inode creation * transaction and provides for atomic labeling of the inode, unlike * the post_create/mkdir/... hooks called by the VFS. The hook function - * is expected to allocate the name and value via kmalloc, with the caller - * being responsible for calling kfree after using them. + * is expected to allocate the value via kmalloc, with the caller + * being responsible for calling kfree after using it. * If the security module does not use security attributes or does * not wish to put a security attribute on this particular inode, * then it should return -EOPNOTSUPP to skip this processing. * @inode contains the inode structure of the newly created inode. * @dir contains the inode structure of the parent directory. * @qstr contains the last path component of the new object - * @name will be set to the allocated name suffix (e.g. selinux). - * @value will be set to the allocated attribute value. - * @len will be set to the length of the value. - * Returns 0 if @name and @value have been successfully set, + * @xattrs contains the full array of xattrs provided by LSMs where + * ->name will be set to the name suffix (e.g. selinux). + * ->value will be set to the allocated attribute value. + * ->value_len will be set to the length of the value. + * Slots in @xattrs need to be reserved by LSMs by providing the number of + * the desired xattrs in the lbs_xattr field of the lsm_blob_sizes + * structure. + * Returns 0 if the requested slots in @xattrs have been successfully set, * -EOPNOTSUPP if no security attribute is needed, or * -ENOMEM on memory allocation failure. * @inode_init_security_anon: @@ -1624,6 +1628,7 @@ struct lsm_blob_sizes { int lbs_ipc; int lbs_msg_msg; int lbs_task; + int lbs_xattr; }; /* diff --git a/security/security.c b/security/security.c index e2857446fd32..26aaa5850867 100644 --- a/security/security.c +++ b/security/security.c @@ -30,8 +30,6 @@ #include #include -#define MAX_LSM_EVM_XATTR 2 - /* How many LSMs were built into the kernel? */ #define LSM_COUNT (__end_lsm_info - __start_lsm_info) @@ -210,6 +208,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed) lsm_set_blob_size(&needed->lbs_msg_msg, &blob_sizes.lbs_msg_msg); lsm_set_blob_size(&needed->lbs_superblock, &blob_sizes.lbs_superblock); lsm_set_blob_size(&needed->lbs_task, &blob_sizes.lbs_task); + lsm_set_blob_size(&needed->lbs_xattr, &blob_sizes.lbs_xattr); } /* Prepare LSM for initialization. */ @@ -346,6 +345,7 @@ static void __init ordered_lsm_init(void) init_debug("msg_msg blob size = %d\n", blob_sizes.lbs_msg_msg); init_debug("superblock blob size = %d\n", blob_sizes.lbs_superblock); init_debug("task blob size = %d\n", blob_sizes.lbs_task); + init_debug("xattr slots = %d\n", blob_sizes.lbs_xattr); /* * Create any kmem_caches needed for blobs @@ -1089,37 +1089,110 @@ int security_dentry_create_files_as(struct dentry *dentry, int mode, } EXPORT_SYMBOL(security_dentry_create_files_as); +/** + * security_check_compact_filled_xattrs - check xattrs and make array contiguous + * @xattrs: xattr array filled by LSMs + * @num_xattrs: length of xattr array + * @num_filled_xattrs: number of already processed xattrs + * + * Ensure that each xattr slot is correctly filled and close the gaps in the + * xattr array if an LSM didn't provide an xattr for which it asked space + * (legitimate case, it might have been loaded but not initialized). An LSM + * might request space in the xattr array for one or multiple xattrs. The LSM + * infrastructure ensures that all requests by LSMs are satisfied. + * + * Track the number of filled xattrs in @num_filled_xattrs, so that it is easy + * to determine whether the currently processed xattr is fine in its position + * (if all previous xattrs were filled) or it should be moved after the last + * filled xattr. + * + * Return: zero if all xattrs are valid, -EINVAL otherwise. + */ +static int security_check_compact_filled_xattrs(struct xattr *xattrs, + int num_xattrs, + int *num_filled_xattrs) +{ + int i; + + for (i = *num_filled_xattrs; i < num_xattrs; i++) { + if ((!xattrs[i].name && xattrs[i].value) || + (xattrs[i].name && !xattrs[i].value)) + return -EINVAL; + + if (!xattrs[i].name) + continue; + + if (i == *num_filled_xattrs) { + (*num_filled_xattrs)++; + continue; + } + + memcpy(xattrs + (*num_filled_xattrs)++, xattrs + i, + sizeof(*xattrs)); + memset(xattrs + i, 0, sizeof(*xattrs)); + } + + return 0; +} + int security_inode_init_security(struct inode *inode, struct inode *dir, const struct qstr *qstr, const initxattrs initxattrs, void *fs_data) { - struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1]; - struct xattr *lsm_xattr, *evm_xattr, *xattr; - int ret; + struct security_hook_list *P; + struct xattr *new_xattrs; + struct xattr *xattr; + int ret = -EOPNOTSUPP, num_filled_xattrs = 0; if (unlikely(IS_PRIVATE(inode))) return 0; + if (!blob_sizes.lbs_xattr) + return 0; + if (!initxattrs) return call_int_hook(inode_init_security, -EOPNOTSUPP, inode, - dir, qstr, NULL, NULL, NULL); - memset(new_xattrs, 0, sizeof(new_xattrs)); - lsm_xattr = new_xattrs; - ret = call_int_hook(inode_init_security, -EOPNOTSUPP, inode, dir, qstr, - &lsm_xattr->name, - &lsm_xattr->value, - &lsm_xattr->value_len); - if (ret) + dir, qstr, NULL); + /* Allocate +1 for EVM and +1 as terminator. */ + new_xattrs = kcalloc(blob_sizes.lbs_xattr + 2, sizeof(*new_xattrs), + GFP_NOFS); + if (!new_xattrs) + return -ENOMEM; + + hlist_for_each_entry(P, &security_hook_heads.inode_init_security, + list) { + ret = P->hook.inode_init_security(inode, dir, qstr, new_xattrs); + if (ret && ret != -EOPNOTSUPP) + goto out; + if (ret == -EOPNOTSUPP) + continue; + /* + * As the number of xattrs reserved by LSMs is not directly + * available, directly use the total number blob_sizes.lbs_xattr + * to keep the code simple, while being not the most efficient + * way. + */ + ret = security_check_compact_filled_xattrs(new_xattrs, + blob_sizes.lbs_xattr, + &num_filled_xattrs); + if (ret < 0) { + ret = -ENOMEM; + goto out; + } + } + + 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); if (ret) goto out; ret = initxattrs(inode, new_xattrs, fs_data); out: for (xattr = new_xattrs; xattr->value != NULL; xattr++) kfree(xattr->value); + kfree(new_xattrs); return (ret == -EOPNOTSUPP) ? 0 : ret; } EXPORT_SYMBOL(security_inode_init_security); diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index f553c370397e..57e5bc7c9ed8 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -104,6 +104,8 @@ #include "audit.h" #include "avc_ss.h" +#define SELINUX_INODE_INIT_XATTRS 1 + struct selinux_state selinux_state; /* SECMARK reference count */ @@ -2868,11 +2870,11 @@ static int selinux_dentry_create_files_as(struct dentry *dentry, int mode, static int selinux_inode_init_security(struct inode *inode, struct inode *dir, const struct qstr *qstr, - const char **name, - void **value, size_t *len) + struct xattr *xattrs) { const struct task_security_struct *tsec = selinux_cred(current_cred()); struct superblock_security_struct *sbsec; + struct xattr *xattr = NULL; u32 newsid, clen; int rc; char *context; @@ -2899,16 +2901,18 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir, !(sbsec->flags & SBLABEL_MNT)) return -EOPNOTSUPP; - if (name) - *name = XATTR_SELINUX_SUFFIX; + if (xattrs) + xattr = xattrs + selinux_blob_sizes.lbs_xattr; + + if (xattr) { + xattr->name = XATTR_SELINUX_SUFFIX; - if (value && len) { rc = security_sid_to_context_force(&selinux_state, newsid, &context, &clen); if (rc) return rc; - *value = context; - *len = clen; + xattr->value = context; + xattr->value_len = clen; } return 0; @@ -6900,6 +6904,7 @@ struct lsm_blob_sizes selinux_blob_sizes __lsm_ro_after_init = { .lbs_ipc = sizeof(struct ipc_security_struct), .lbs_msg_msg = sizeof(struct msg_security_struct), .lbs_superblock = sizeof(struct superblock_security_struct), + .lbs_xattr = SELINUX_INODE_INIT_XATTRS, }; #ifdef CONFIG_PERF_EVENTS diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index b6306d71c908..a7c3e4284754 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -52,6 +52,8 @@ #define SMK_RECEIVING 1 #define SMK_SENDING 2 +#define SMACK_INODE_INIT_XATTRS 4 + #ifdef SMACK_IPV6_PORT_LABELING static DEFINE_MUTEX(smack_ipv6_lock); static LIST_HEAD(smk_ipv6_port_list); @@ -939,26 +941,27 @@ static int smack_inode_alloc_security(struct inode *inode) * @inode: the newly created inode * @dir: containing directory object * @qstr: unused - * @name: where to put the attribute name - * @value: where to put the attribute value - * @len: where to put the length of the attribute + * @xattrs: where to put the attribute * * Returns 0 if it all works out, -ENOMEM if there's no memory */ static int smack_inode_init_security(struct inode *inode, struct inode *dir, - const struct qstr *qstr, const char **name, - void **value, size_t *len) + const struct qstr *qstr, + struct xattr *xattrs) { struct inode_smack *issp = smack_inode(inode); struct smack_known *skp = smk_of_current(); struct smack_known *isp = smk_of_inode(inode); struct smack_known *dsp = smk_of_inode(dir); + struct xattr *xattr = NULL; int may; - if (name) - *name = XATTR_SMACK_SUFFIX; + if (xattrs) + xattr = xattrs + smack_blob_sizes.lbs_xattr; + + if (xattr) { + xattr->name = XATTR_SMACK_SUFFIX; - if (value && len) { rcu_read_lock(); may = smk_access_entry(skp->smk_known, dsp->smk_known, &skp->smk_rules); @@ -976,11 +979,11 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir, issp->smk_flags |= SMK_INODE_CHANGED; } - *value = kstrdup(isp->smk_known, GFP_NOFS); - if (*value == NULL) + xattr->value = kstrdup(isp->smk_known, GFP_NOFS); + if (xattr->value == NULL) return -ENOMEM; - *len = strlen(isp->smk_known); + xattr->value_len = strlen(isp->smk_known); } return 0; @@ -4785,6 +4788,7 @@ struct lsm_blob_sizes smack_blob_sizes __lsm_ro_after_init = { .lbs_ipc = sizeof(struct smack_known *), .lbs_msg_msg = sizeof(struct smack_known *), .lbs_superblock = sizeof(struct superblock_smack), + .lbs_xattr = SMACK_INODE_INIT_XATTRS, }; static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {