EVM: turn evm_config_xattrnames into a list

Use a list of xattrs rather than an array - this makes it easier to
extend the list at runtime.
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: James Morris <james.morris@microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

security/integrity/evm/evm.h

@@ -30,6 +30,11 @@
 #define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP_COMPLETE | \
 		       EVM_ALLOW_METADATA_WRITES)
 
+struct xattr_list {
+	struct list_head list;
+	char *name;
+};
+
 extern int evm_initialized;
 
 #define EVM_ATTR_FSUUID		0x0001
@@ -40,7 +45,7 @@ extern struct crypto_shash *hmac_tfm;
 extern struct crypto_shash *hash_tfm;
 
 /* List of EVM protected security xattrs */
-extern char *evm_config_xattrnames[];
+extern struct list_head evm_config_xattrnames;
 
 int evm_init_key(void);
 int evm_update_evmxattr(struct dentry *dentry,

security/integrity/evm/evm_crypto.c

@@ -192,8 +192,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
 				char type, char *digest)
 {
 	struct inode *inode = d_backing_inode(dentry);
+	struct xattr_list *xattr;
 	struct shash_desc *desc;
-	char **xattrname;
 	size_t xattr_size = 0;
 	char *xattr_value = NULL;
 	int error;
@@ -208,14 +208,14 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
 		return PTR_ERR(desc);
 
 	error = -ENODATA;
-	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
+	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
 		bool is_ima = false;
 
-		if (strcmp(*xattrname, XATTR_NAME_IMA) == 0)
+		if (strcmp(xattr->name, XATTR_NAME_IMA) == 0)
 			is_ima = true;
 
 		if ((req_xattr_name && req_xattr_value)
-		    && !strcmp(*xattrname, req_xattr_name)) {
+		    && !strcmp(xattr->name, req_xattr_name)) {
 			error = 0;
 			crypto_shash_update(desc, (const u8 *)req_xattr_value,
 					     req_xattr_value_len);
@@ -223,7 +223,7 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
 				ima_present = true;
 			continue;
 		}
-		size = vfs_getxattr_alloc(dentry, *xattrname,
+		size = vfs_getxattr_alloc(dentry, xattr->name,
 					  &xattr_value, xattr_size, GFP_NOFS);
 		if (size == -ENOMEM) {
 			error = -ENOMEM;

security/integrity/evm/evm_main.c

@@ -35,28 +35,29 @@ static const char * const integrity_status_msg[] = {
 };
 int evm_hmac_attrs;
 
-char *evm_config_xattrnames[] = {
+static struct xattr_list evm_config_default_xattrnames[] __ro_after_init = {
 #ifdef CONFIG_SECURITY_SELINUX
-	XATTR_NAME_SELINUX,
+	{.name = XATTR_NAME_SELINUX},
 #endif
 #ifdef CONFIG_SECURITY_SMACK
-	XATTR_NAME_SMACK,
+	{.name = XATTR_NAME_SMACK},
 #ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
-	XATTR_NAME_SMACKEXEC,
-	XATTR_NAME_SMACKTRANSMUTE,
-	XATTR_NAME_SMACKMMAP,
+	{.name = XATTR_NAME_SMACKEXEC},
+	{.name = XATTR_NAME_SMACKTRANSMUTE},
+	{.name = XATTR_NAME_SMACKMMAP},
 #endif
 #endif
 #ifdef CONFIG_SECURITY_APPARMOR
-	XATTR_NAME_APPARMOR,
+	{.name = XATTR_NAME_APPARMOR},
 #endif
 #ifdef CONFIG_IMA_APPRAISE
-	XATTR_NAME_IMA,
+	{.name = XATTR_NAME_IMA},
 #endif
-	XATTR_NAME_CAPS,
-	NULL
+	{.name = XATTR_NAME_CAPS},
 };
 
+LIST_HEAD(evm_config_xattrnames);
+
 static int evm_fixmode;
 static int __init evm_set_fixmode(char *str)
 {
@@ -68,6 +69,17 @@ __setup("evm=", evm_set_fixmode);
 
 static void __init evm_init_config(void)
 {
+	int i, xattrs;
+
+	xattrs = ARRAY_SIZE(evm_config_default_xattrnames);
+
+	pr_info("Initialising EVM extended attributes:\n");
+	for (i = 0; i < xattrs; i++) {
+		pr_info("%s\n", evm_config_default_xattrnames[i].name);
+		list_add_tail(&evm_config_default_xattrnames[i].list,
+			      &evm_config_xattrnames);
+	}
+
 #ifdef CONFIG_EVM_ATTR_FSUUID
 	evm_hmac_attrs |= EVM_ATTR_FSUUID;
 #endif
@@ -82,15 +94,15 @@ static bool evm_key_loaded(void)
 static int evm_find_protected_xattrs(struct dentry *dentry)
 {
 	struct inode *inode = d_backing_inode(dentry);
-	char **xattr;
+	struct xattr_list *xattr;
 	int error;
 	int count = 0;
 
 	if (!(inode->i_opflags & IOP_XATTR))
 		return -EOPNOTSUPP;
 
-	for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
-		error = __vfs_getxattr(dentry, inode, *xattr, NULL, 0);
+	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
+		error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
 		if (error < 0) {
 			if (error == -ENODATA)
 				continue;
@@ -211,24 +223,25 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 
 static int evm_protected_xattr(const char *req_xattr_name)
 {
-	char **xattrname;
 	int namelen;
 	int found = 0;
+	struct xattr_list *xattr;
 
 	namelen = strlen(req_xattr_name);
-	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
-		if ((strlen(*xattrname) == namelen)
-		    && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
+	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
+		if ((strlen(xattr->name) == namelen)
+		    && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
 			found = 1;
 			break;
 		}
 		if (strncmp(req_xattr_name,
-			    *xattrname + XATTR_SECURITY_PREFIX_LEN,
+			    xattr->name + XATTR_SECURITY_PREFIX_LEN,
 			    strlen(req_xattr_name)) == 0) {
 			found = 1;
 			break;
 		}
 	}
+
 	return found;
 }
 
@@ -544,35 +557,35 @@ void __init evm_load_x509(void)
 static int __init init_evm(void)
 {
 	int error;
+	struct list_head *pos, *q;
+	struct xattr_list *xattr;
 
 	evm_init_config();
 
 	error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
 	if (error)
-		return error;
+		goto error;
 
 	error = evm_init_secfs();
 	if (error < 0) {
 		pr_info("Error registering secfs\n");
-		return error;
+		goto error;
 	}
 
-	return 0;
-}
-
-/*
- * evm_display_config - list the EVM protected security extended attributes
- */
-static int __init evm_display_config(void)
-{
-	char **xattrname;
+error:
+	if (error != 0) {
+		if (!list_empty(&evm_config_xattrnames)) {
+			list_for_each_safe(pos, q, &evm_config_xattrnames) {
+				xattr = list_entry(pos, struct xattr_list,
+						   list);
+				list_del(pos);
+			}
+		}
+	}
 
-	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
-		pr_info("%s\n", *xattrname);
-	return 0;
+	return error;
 }
 
-pure_initcall(evm_display_config);
 late_initcall(init_evm);
 
 MODULE_DESCRIPTION("Extended Verification Module");