ima,evm: move initcalls to the LSM framework

This patch converts IMA and EVM to use the LSM frameworks's initcall
mechanism. It moved the integrity_fs_init() call to ima_fs_init() and
evm_init_secfs(), to work around the fact that there is no "integrity" LSM,
and introduced integrity_fs_fini() to remove the integrity directory, if
empty. Both integrity_fs_init() and integrity_fs_fini() support the
scenario of being called by both the IMA and EVM LSMs.

This patch does not touch any of the platform certificate code that
lives under the security/integrity/platform_certs directory as the
IMA/EVM developers would prefer to address that in a future patchset.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Acked-by: Mimi Zohar <zohar@linux.ibm.com>
[PM: adjust description as discussed over email]
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/integrity/evm/evm_main.c

@@ -1179,6 +1179,5 @@ DEFINE_LSM(evm) = {
 	.init = init_evm_lsm,
 	.order = LSM_ORDER_LAST,
 	.blobs = &evm_blob_sizes,
+	.initcall_late = init_evm,
 };
-
-late_initcall(init_evm);

security/integrity/evm/evm_secfs.c

@@ -302,10 +302,16 @@ int __init evm_init_secfs(void)
 	int error = 0;
 	struct dentry *dentry;
 
-	evm_dir = securityfs_create_dir("evm", integrity_dir);
+	error = integrity_fs_init();
-	if (IS_ERR(evm_dir))
+	if (error < 0)
 		return -EFAULT;
 
+	evm_dir = securityfs_create_dir("evm", integrity_dir);
+	if (IS_ERR(evm_dir)) {
+		error = -EFAULT;
+		goto out;
+	}
+
 	dentry = securityfs_create_file("evm", 0660,
 				      evm_dir, NULL, &evm_key_ops);
 	if (IS_ERR(dentry)) {
@@ -329,5 +335,6 @@ int __init evm_init_secfs(void)
 out:
 	securityfs_remove(evm_symlink);
 	securityfs_remove(evm_dir);
+	integrity_fs_fini();
 	return error;
 }

security/integrity/iint.c

@@ -42,8 +42,11 @@ void __init integrity_load_keys(void)
 		evm_load_x509();
 }
 
-static int __init integrity_fs_init(void)
+int __init integrity_fs_init(void)
 {
+	if (integrity_dir)
+		return 0;
+
 	integrity_dir = securityfs_create_dir("integrity", NULL);
 	if (IS_ERR(integrity_dir)) {
 		int ret = PTR_ERR(integrity_dir);
@@ -58,4 +61,11 @@ static int __init integrity_fs_init(void)
 	return 0;
 }
 
-late_initcall(integrity_fs_init)
+void __init integrity_fs_fini(void)
+{
+	if (!integrity_dir || !simple_empty(integrity_dir))
+		return;
+
+	securityfs_remove(integrity_dir);
+	integrity_dir = NULL;
+}

security/integrity/ima/ima_fs.c

@@ -499,9 +499,15 @@ int __init ima_fs_init(void)
 	struct dentry *dentry;
 	int ret;
 
+	ret = integrity_fs_init();
+	if (ret < 0)
+		return ret;
+
 	ima_dir = securityfs_create_dir("ima", integrity_dir);
-	if (IS_ERR(ima_dir))
+	if (IS_ERR(ima_dir)) {
-		return PTR_ERR(ima_dir);
+		ret = PTR_ERR(ima_dir);
+		goto out;
+	}
 
 	ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
 						NULL);
@@ -555,6 +561,7 @@ int __init ima_fs_init(void)
 out:
 	securityfs_remove(ima_symlink);
 	securityfs_remove(ima_dir);
+	integrity_fs_fini();
 
 	return ret;
 }

security/integrity/ima/ima_main.c

@@ -1283,6 +1283,6 @@ DEFINE_LSM(ima) = {
 	.init = init_ima_lsm,
 	.order = LSM_ORDER_LAST,
 	.blobs = &ima_blob_sizes,
+	/* Start IMA after the TPM is available */
+	.initcall_late = init_ima,
 };
-
-late_initcall(init_ima);	/* Start IMA after the TPM is available */

security/integrity/integrity.h

@@ -114,6 +114,8 @@ struct ima_file_id {
 
 int integrity_kernel_read(struct file *file, loff_t offset,
 			  void *addr, unsigned long count);
+int __init integrity_fs_init(void);
+void __init integrity_fs_fini(void);
 
 #define INTEGRITY_KEYRING_EVM		0
 #define INTEGRITY_KEYRING_IMA		1