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From:   Roberto Sassu <roberto.sassu@huaweicloud.com>
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        linux-integrity@vger.kernel.org, keyrings@vger.kernel.org,
        selinux@vger.kernel.org, Roberto Sassu <roberto.sassu@huawei.com>
Subject: [PATCH v4 22/23] integrity: Move integrity functions to the LSM infrastructure
Date:   Fri, 27 Oct 2023 10:42:33 +0200
Message-Id: <20231027084234.485243-3-roberto.sassu@huaweicloud.com>
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From: Roberto Sassu <roberto.sassu@huawei.com>

Remove hardcoded calls to integrity functions from the LSM infrastructure
and, instead, register them in integrity_lsm_init() with the IMA or EVM
LSM ID (the first non-NULL returned by ima_get_lsm_id() and
evm_get_lsm_id()).

Also move the global declaration of integrity_inode_get() to
security/integrity/integrity.h, so that the function can be still called by
IMA.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 include/linux/integrity.h      | 26 --------------------------
 security/integrity/iint.c      | 30 +++++++++++++++++++++++++++++-
 security/integrity/integrity.h |  7 +++++++
 security/security.c            |  9 +--------
 4 files changed, 37 insertions(+), 35 deletions(-)

diff --git a/include/linux/integrity.h b/include/linux/integrity.h
index 2ea0f2f65ab6..afaae7ad26f4 100644
--- a/include/linux/integrity.h
+++ b/include/linux/integrity.h
@@ -21,38 +21,12 @@ enum integrity_status {
 
 /* List of EVM protected security xattrs */
 #ifdef CONFIG_INTEGRITY
-extern struct integrity_iint_cache *integrity_inode_get(struct inode *inode);
-extern void integrity_inode_free(struct inode *inode);
 extern void __init integrity_load_keys(void);
 
 #else
-static inline struct integrity_iint_cache *
-				integrity_inode_get(struct inode *inode)
-{
-	return NULL;
-}
-
-static inline void integrity_inode_free(struct inode *inode)
-{
-	return;
-}
-
 static inline void integrity_load_keys(void)
 {
 }
 #endif /* CONFIG_INTEGRITY */
 
-#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
-
-extern int integrity_kernel_module_request(char *kmod_name);
-
-#else
-
-static inline int integrity_kernel_module_request(char *kmod_name)
-{
-	return 0;
-}
-
-#endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */
-
 #endif /* _LINUX_INTEGRITY_H */
diff --git a/security/integrity/iint.c b/security/integrity/iint.c
index 3d9cf5041739..31a0fda3f1a1 100644
--- a/security/integrity/iint.c
+++ b/security/integrity/iint.c
@@ -171,7 +171,7 @@ struct integrity_iint_cache *integrity_inode_get(struct inode *inode)
  *
  * Free the integrity information(iint) associated with an inode.
  */
-void integrity_inode_free(struct inode *inode)
+static void integrity_inode_free(struct inode *inode)
 {
 	struct integrity_iint_cache *iint;
 
@@ -193,11 +193,39 @@ static void iint_init_once(void *foo)
 	memset(iint, 0, sizeof(*iint));
 }
 
+static struct security_hook_list integrity_hooks[] __ro_after_init = {
+	LSM_HOOK_INIT(inode_free_security, integrity_inode_free),
+#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
+	LSM_HOOK_INIT(kernel_module_request, integrity_kernel_module_request),
+#endif
+};
+
+/*
+ * Perform the initialization of the 'integrity', 'ima' and 'evm' LSMs to
+ * ensure that the management of integrity metadata is working at the time
+ * IMA and EVM hooks are registered to the LSM infrastructure, and to keep
+ * the original ordering of IMA and EVM functions as when they were hardcoded.
+ */
 static int __init integrity_lsm_init(void)
 {
+	const struct lsm_id *lsmid;
+
 	iint_cache =
 	    kmem_cache_create("iint_cache", sizeof(struct integrity_iint_cache),
 			      0, SLAB_PANIC, iint_init_once);
+	/*
+	 * Obtain either the IMA or EVM LSM ID to register integrity-specific
+	 * hooks under that LSM, since there is no LSM ID assigned to the
+	 * 'integrity' LSM.
+	 */
+	lsmid = ima_get_lsm_id();
+	if (!lsmid)
+		lsmid = evm_get_lsm_id();
+	/* No point in continuing, since both IMA and EVM are disabled. */
+	if (!lsmid)
+		return 0;
+
+	security_add_hooks(integrity_hooks, ARRAY_SIZE(integrity_hooks), lsmid);
 	init_ima_lsm();
 	init_evm_lsm();
 	return 0;
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 7534ec06324e..e4df82d6f6e7 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -180,6 +180,7 @@ struct integrity_iint_cache {
  * integrity data associated with an inode.
  */
 struct integrity_iint_cache *integrity_iint_find(struct inode *inode);
+struct integrity_iint_cache *integrity_inode_get(struct inode *inode);
 
 int integrity_kernel_read(struct file *file, loff_t offset,
 			  void *addr, unsigned long count);
@@ -266,12 +267,18 @@ static inline int __init integrity_load_cert(const unsigned int id,
 #ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
 int asymmetric_verify(struct key *keyring, const char *sig,
 		      int siglen, const char *data, int datalen);
+int integrity_kernel_module_request(char *kmod_name);
 #else
 static inline int asymmetric_verify(struct key *keyring, const char *sig,
 				    int siglen, const char *data, int datalen)
 {
 	return -EOPNOTSUPP;
 }
+
+static inline int integrity_kernel_module_request(char *kmod_name)
+{
+	return 0;
+}
 #endif
 
 #ifdef CONFIG_IMA_APPRAISE_MODSIG
diff --git a/security/security.c b/security/security.c
index 5bbeedd534b6..c70664c947be 100644
--- a/security/security.c
+++ b/security/security.c
@@ -19,7 +19,6 @@
 #include <linux/kernel.h>
 #include <linux/kernel_read_file.h>
 #include <linux/lsm_hooks.h>
-#include <linux/integrity.h>
 #include <linux/fsnotify.h>
 #include <linux/mman.h>
 #include <linux/mount.h>
@@ -1590,7 +1589,6 @@ static void inode_free_by_rcu(struct rcu_head *head)
  */
 void security_inode_free(struct inode *inode)
 {
-	integrity_inode_free(inode);
 	call_void_hook(inode_free_security, inode);
 	/*
 	 * The inode may still be referenced in a path walk and
@@ -3175,12 +3173,7 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode)
  */
 int security_kernel_module_request(char *kmod_name)
 {
-	int ret;
-
-	ret = call_int_hook(kernel_module_request, 0, kmod_name);
-	if (ret)
-		return ret;
-	return integrity_kernel_module_request(kmod_name);
+	return call_int_hook(kernel_module_request, 0, kmod_name);
 }
 
 /**
-- 
2.34.1