From patchwork Fri Oct 21 15:14:53 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Nicolas Bouchinet X-Patchwork-Id: 13014900 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 A1B51C4332F for ; Fri, 21 Oct 2022 15:16:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230333AbiJUPQD (ORCPT ); Fri, 21 Oct 2022 11:16:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230259AbiJUPPs (ORCPT ); Fri, 21 Oct 2022 11:15:48 -0400 Received: from relay1-d.mail.gandi.net (relay1-d.mail.gandi.net [217.70.183.193]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5A869F6812; Fri, 21 Oct 2022 08:15:03 -0700 (PDT) Received: (Authenticated sender: nicolas.bouchinet@clip-os.org) by mail.gandi.net (Postfix) with ESMTPSA id 067F3240009; Fri, 21 Oct 2022 15:14:54 +0000 (UTC) Date: Fri, 21 Oct 2022 17:14:53 +0200 From: Nicolas Bouchinet To: linux-integrity@vger.kernel.org Cc: philippe.trebuchet@ssi.gouv.fr, zohar@linux.ibm.com, 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 Subject: [PATCH v2] evm: Correct inode_init_security hooks behaviors Message-ID: MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: 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. Adds a `call_int_hook_xattr` macro that fetches and feed the `new_xattrs` array with every called hook xattr values. Adds a `evm_init_hmacs` function which init the EVM hmac using every entry of the array contrary to `evm_init_hmac`. Fixes the `evm_inode_init_security` function to use `evm_init_hmacs`. The `MAX_LSM_EVM_XATTR` value has been raised to 5 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: stable@vger.kernel.org Signed-off-by: Nicolas Bouchinet --- Changes since v1: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/ * The `call_int_hook_xattr` macro has been inlined into the `security_inode_init_security` hook (as suggested by Paul Moor, Mickaël Salaün and Casey Schaufler). * The MAX_LSM_EVM_XATTR value is processed based on compiled LSMs (as proposed by Casey Schaufler). * Various typos and cosmetic changes has been fixed (as suggested by Mickaël Salaün) * A MAX_LSM_EVM_XATTR test has been wrapped in a WAN_ON_ONCE macro (as suggested by Mickaël Salaün). --- include/linux/lsm_hook_defs.h | 2 +- include/linux/lsm_hooks.h | 4 ++-- security/integrity/evm/evm.h | 2 ++ security/integrity/evm/evm_crypto.c | 22 ++++++++++++++++++++++ security/integrity/evm/evm_main.c | 9 +++++---- security/security.c | 28 +++++++++++++++++++++------- 6 files changed, 53 insertions(+), 14 deletions(-) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 806448173033..e5dd0c0f6345 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -111,7 +111,7 @@ 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, +LSM_HOOK(int, -EOPNOTSUPP, inode_init_security, struct inode *inode, struct inode *dir, const struct qstr *qstr, const char **name, void **value, size_t *len) LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode, diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 84a0d7e02176..95aff9383de1 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -229,8 +229,8 @@ * 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. diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h index f8b8c5004fc7..a2f9886e924d 100644 --- a/security/integrity/evm/evm.h +++ b/security/integrity/evm/evm.h @@ -60,6 +60,8 @@ int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name, struct evm_digest *data); int evm_init_hmac(struct inode *inode, const struct xattr *xattr, char *hmac_val); +int evm_init_hmacs(struct inode *inode, const struct xattr *xattrs, + char *hmac_val); int evm_init_secfs(void); #endif diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index 708de9656bbd..db6868875e09 100644 --- a/security/integrity/evm/evm_crypto.c +++ b/security/integrity/evm/evm_crypto.c @@ -385,6 +385,28 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name, return rc; } +int evm_protected_xattr(const char *req_xattr_name); + +int evm_init_hmacs(struct inode *inode, const struct xattr *lsm_xattrs, + char *hmac_val) +{ + struct shash_desc *desc; + + desc = init_desc(EVM_XATTR_HMAC, HASH_ALGO_SHA1); + if (IS_ERR(desc)) { + pr_info("init_desc failed\n"); + return PTR_ERR(desc); + } + + for (int i = 0; lsm_xattrs[i].value != NULL; i++) { + if (evm_protected_xattr(lsm_xattrs[i].name)) + crypto_shash_update(desc, lsm_xattrs[i].value, lsm_xattrs[i].value_len); + } + hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val); + kfree(desc); + return 0; +} + int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr, char *hmac_val) { diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 2e6fb6e2ffd2..4f89b9eaf028 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -284,6 +284,8 @@ static int evm_protected_xattr_common(const char *req_xattr_name, int found = 0; struct xattr_list *xattr; + if (!req_xattr_name) + return found; namelen = strlen(req_xattr_name); list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { if (!all_xattrs && !xattr->enabled) @@ -305,7 +307,7 @@ static int evm_protected_xattr_common(const char *req_xattr_name, return found; } -static int evm_protected_xattr(const char *req_xattr_name) +int evm_protected_xattr(const char *req_xattr_name) { return evm_protected_xattr_common(req_xattr_name, false); } @@ -841,8 +843,7 @@ int evm_inode_init_security(struct inode *inode, struct evm_xattr *xattr_data; int rc; - if (!(evm_initialized & EVM_INIT_HMAC) || - !evm_protected_xattr(lsm_xattr->name)) + if (!(evm_initialized & EVM_INIT_HMAC)) return 0; xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); @@ -850,7 +851,7 @@ int evm_inode_init_security(struct inode *inode, return -ENOMEM; xattr_data->data.type = EVM_XATTR_HMAC; - rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest); + rc = evm_init_hmacs(inode, lsm_xattr, xattr_data->digest); if (rc < 0) goto out; diff --git a/security/security.c b/security/security.c index 14d30fec8a00..cf11bd7d6a1b 100644 --- a/security/security.c +++ b/security/security.c @@ -30,7 +30,11 @@ #include #include -#define MAX_LSM_EVM_XATTR 2 +#define MAX_LSM_EVM_XATTR \ + ((IS_ENABLED(CONFIG_EVM) ? 1 : 0) + \ + (IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \ + (IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \ + (IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0)) /* How many LSMs were built into the kernel? */ #define LSM_COUNT (__end_lsm_info - __start_lsm_info) @@ -1091,9 +1095,11 @@ int security_inode_init_security(struct inode *inode, struct inode *dir, const struct qstr *qstr, const initxattrs initxattrs, void *fs_data) { + int i = 0; + int ret = -EOPNOTSUPP; struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1]; struct xattr *lsm_xattr, *evm_xattr, *xattr; - int ret; + struct security_hook_list *hook_ptr; if (unlikely(IS_PRIVATE(inode))) return 0; @@ -1103,15 +1109,23 @@ int security_inode_init_security(struct inode *inode, struct inode *dir, 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); + hlist_for_each_entry(hook_ptr, &security_hook_heads.inode_init_security, list) { + ret = hook_ptr->hook.inode_init_security(inode, dir, qstr, &lsm_xattr->name, + &lsm_xattr->value, &lsm_xattr->value_len); + if (ret == -EOPNOTSUPP) + continue; + if (WARN_ON_ONCE(i >= MAX_LSM_EVM_XATTR)) + ret = -ENOMEM; + if (ret != 0) + break; + lsm_xattr++; + i++; + } if (ret) 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, evm_xattr); if (ret) goto out; ret = initxattrs(inode, new_xattrs, fs_data);