From patchwork Wed Mar 29 13:04:13 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 13192364 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 3AD89C6FD18 for ; Wed, 29 Mar 2023 13:05:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230125AbjC2NFj (ORCPT ); Wed, 29 Mar 2023 09:05:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50672 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230133AbjC2NF2 (ORCPT ); Wed, 29 Mar 2023 09:05:28 -0400 Received: from frasgout11.his.huawei.com (frasgout11.his.huawei.com [14.137.139.23]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 691AD2D41; Wed, 29 Mar 2023 06:05:25 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.18.147.229]) by frasgout11.his.huawei.com (SkyGuard) with ESMTP id 4Pmml13jKpz9v7gT; Wed, 29 Mar 2023 20:56:13 +0800 (CST) Received: from huaweicloud.com (unknown [10.204.63.22]) by APP1 (Coremail) with SMTP id LxC2BwCXFABgNyRk2AzcAQ--.1625S4; Wed, 29 Mar 2023 14:05:01 +0100 (CET) From: Roberto Sassu To: 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: reiserfs-devel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, bpf@vger.kernel.org, kpsingh@kernel.org, keescook@chromium.org, nicolas.bouchinet@clip-os.org, Roberto Sassu Subject: [PATCH v9 2/4] security: Allow all LSMs to provide xattrs for inode_init_security hook Date: Wed, 29 Mar 2023 15:04:13 +0200 Message-Id: <20230329130415.2312521-3-roberto.sassu@huaweicloud.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230329130415.2312521-1-roberto.sassu@huaweicloud.com> References: <20230329130415.2312521-1-roberto.sassu@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: LxC2BwCXFABgNyRk2AzcAQ--.1625S4 X-Coremail-Antispam: 1UD129KBjvAXoW3Kr1DAr18Ary5XFyUJw1rXrb_yoW8Gw4fZo WxJwnrXr40qr1xKrWFg3Z7JFZruayrWr4fJr1Fvr45A3Zxtw1UCw13Xay8Xa13WryrKr48 t3s7Aa48XrZFqF98n29KB7ZKAUJUUUU8529EdanIXcx71UUUUU7v73VFW2AGmfu7bjvjm3 AaLaJ3UjIYCTnIWjp_UUUO57kC6x804xWl14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK 8VAvwI8IcIk0rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jr yl82xGYIkIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_JFI_Gr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26r4j6F4UM28EF7xvwVC2z280aVCY1x0267AK xVW8Jr0_Cr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7 xfMcIj6xIIjxv20xvE14v26r106r15McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Y z7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1lc7CjxVAaw2 AFwI0_GFv_Wryl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAq x4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r4a6r W5MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_JFI_Gr1lIxAIcVC0I7IYx2IY6xkF 7I0E14v26r4UJVWxJr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14 v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr1j6F4UJbIYCTnIWIevJa73UjIFyTuY vjxUxeHqDUUUU X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAQALBF1jj4tPTAAAs3 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: bpf@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_count 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 new_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. Also, pass to the hook the number of xattrs filled by each LSM, so that there are no gaps when the next LSM fills the array. Gaps might occur because an LSM can legitimately request xattrs to the LSM infrastructure, but not fill the reserved slots, if it was not initialized. Update the documentation of security_inode_init_security() to reflect the changes, and fix the description of the xattr name, as it is not allocated anymore. On the security_inode_init_security() side, ensure that if LSMs returned zero from the hook, they correctly filled a new_xattrs slot. Consequently, change the default return value of the hook to -EOPNOTSUPP, so that BPF LSM returns that, and does not cause security_inode_init_security() to fail. Finally, adapt both SELinux and Smack to use the new definition of the inode_init_security hook, and to fill the reserved slots in the xattr array. Introduce the lsm_find_xattr_slot() helper to retrieve an available slot to fill, and to increment the number of filled slots. Move the xattr->name assignment after the xattr->value one, so that it is done only in case of successful memory allocation. For Smack, also reserve space for the other defined xattrs although they are not set yet in smack_inode_init_security(). Reported-by: Nicolas Bouchinet (EVM crash) Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/ Signed-off-by: Roberto Sassu --- include/linux/lsm_hook_defs.h | 6 +-- include/linux/lsm_hooks.h | 14 ++++++ security/security.c | 92 +++++++++++++++++++++++++++-------- security/selinux/hooks.c | 18 ++++--- security/smack/smack_lsm.c | 33 ++++++++----- 5 files changed, 120 insertions(+), 43 deletions(-) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 6bb55e61e8e..1fd95db0087 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -111,9 +111,9 @@ LSM_HOOK(int, 0, path_notify, const struct path *path, u64 mask, unsigned int obj_type) 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) +LSM_HOOK(int, -EOPNOTSUPP, inode_init_security, struct inode *inode, + struct inode *dir, const struct qstr *qstr, struct xattr *xattrs, + int *num_filled_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 c2be66c669a..b60de5f2f34 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -28,6 +28,7 @@ #include #include #include +#include union security_list_options { #define LSM_HOOK(RET, DEFAULT, NAME, ...) RET (*NAME)(__VA_ARGS__); @@ -63,8 +64,21 @@ struct lsm_blob_sizes { int lbs_ipc; int lbs_msg_msg; int lbs_task; + int lbs_xattr_count; /* number of xattr slots in new_xattrs array */ }; +/* + * Retrieve the first available slot to fill with an xattr, and increment + * the number of filled slots. + */ +static inline struct xattr *lsm_find_xattr_slot(struct xattr *xattrs, + int *num_filled_xattrs) +{ + if (unlikely(!xattrs)) + return NULL; + return xattrs + (*num_filled_xattrs)++; +} + /* * LSM_RET_VOID is used as the default value in LSM_HOOK definitions for void * LSM hooks (in include/linux/lsm_hook_defs.h). diff --git a/security/security.c b/security/security.c index f4170efcddd..be33d643a81 100644 --- a/security/security.c +++ b/security/security.c @@ -31,8 +31,6 @@ #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) @@ -212,6 +210,8 @@ 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_count, + &blob_sizes.lbs_xattr_count); } /* Prepare LSM for initialization. */ @@ -378,6 +378,7 @@ 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_count); /* * Create any kmem_caches needed for blobs @@ -1591,11 +1592,15 @@ EXPORT_SYMBOL(security_dentry_create_files_as); * created inode and set up the incore security field for the new inode. 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. 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. + * hooks called by the VFS. The hook function is expected to populate the + * @xattrs array, by calling lsm_find_xattr_slot() to retrieve the slots + * reserved by the security module with the lbs_xattr_count field of the + * lsm_blob_sizes structure. For each slot, the hook function should set ->name + * to the attribute name suffix (e.g. selinux), to allocate ->value (will be + * freed by the caller) and set it to the attribute value, to set ->value_len to + * the length of the value. 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. * * Return: Returns 0 on success, -EOPNOTSUPP if no security attribute is * needed, or -ENOMEM on memory allocation failure. @@ -1604,33 +1609,80 @@ 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 num_filled_xattrs = 0, old_num_filled_xattrs; + int ret = -EOPNOTSUPP, i; if (unlikely(IS_PRIVATE(inode))) return 0; + if (!blob_sizes.lbs_xattr_count) + 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, NULL); + /* Allocate +1 for EVM and +1 as terminator. */ + new_xattrs = kcalloc(blob_sizes.lbs_xattr_count + 2, + sizeof(*new_xattrs), GFP_NOFS); + if (!new_xattrs) + return -ENOMEM; + + hlist_for_each_entry(P, &security_hook_heads.inode_init_security, + list) { + old_num_filled_xattrs = num_filled_xattrs; + + ret = P->hook.inode_init_security(inode, dir, qstr, new_xattrs, + &num_filled_xattrs); + if (ret && ret != -EOPNOTSUPP) + goto out; + /* + * As documented in lsm_hooks.h, -EOPNOTSUPP in this context + * means that the LSM is not willing to provide an xattr, not + * that it wants to signal an error. Thus, continue to invoke + * the remaining LSMs. + */ + if (ret == -EOPNOTSUPP) + continue; + + /* LSM should fill new_xattrs if it returns zero. */ + if (old_num_filled_xattrs == num_filled_xattrs) { + WARN_ONCE(1, "LSM %s: returned zero but didn't fill any slot\n", + P->lsm); + ret = -EINVAL; + goto out; + } + + /* + * For filled xattr slots, name and value must be non-NULL. + * + * NULL value is interpreted by filesystems as a remove op, see + * ext4_xattr_set_handle() for more details. + */ + for (i = old_num_filled_xattrs; i < num_filled_xattrs; i++) { + if (!new_xattrs[i].name || !new_xattrs[i].value) { + WARN_ONCE(1, "LSM %s: NULL xattr name and/or value\n", + P->lsm); + ret = -EINVAL; + 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 9a5bdfc2131..dc349cf34e8 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 +2870,12 @@ 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, + int *num_filled_xattrs) { const struct task_security_struct *tsec = selinux_cred(current_cred()); struct superblock_security_struct *sbsec; + struct xattr *xattr = lsm_find_xattr_slot(xattrs, num_filled_xattrs); u32 newsid, clen; int rc; char *context; @@ -2899,16 +2902,14 @@ 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 (value && len) { + if (xattr) { 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; + xattr->name = XATTR_SELINUX_SUFFIX; } return 0; @@ -6918,6 +6919,7 @@ 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_count = SELINUX_INODE_INIT_XATTRS, }; #ifdef CONFIG_PERF_EVENTS diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index cfcbb748da2..ba10f4e8632 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -52,6 +52,15 @@ #define SMK_RECEIVING 1 #define SMK_SENDING 2 +/* + * Smack uses multiple xattrs. + * SMACK64 - for access control, SMACK64EXEC - label for the program, + * SMACK64MMAP - controls library loading, + * SMACK64TRANSMUTE - label initialization, + * Not saved on files - SMACK64IPIN and SMACK64IPOUT + */ +#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 +948,24 @@ 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 attributes + * @num_filled_xattrs: current number of filled xattrs (updated) * * 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, + int *num_filled_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 = lsm_find_xattr_slot(xattrs, num_filled_xattrs); int may; - if (name) - *name = XATTR_SMACK_SUFFIX; - - if (value && len) { + if (xattr) { rcu_read_lock(); may = smk_access_entry(skp->smk_known, dsp->smk_known, &skp->smk_rules); @@ -976,11 +983,12 @@ 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); + xattr->name = XATTR_SMACK_SUFFIX; } return 0; @@ -4854,6 +4862,7 @@ 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_count = SMACK_INODE_INIT_XATTRS, }; static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {