KEYS: fix "ca_keys=" partial key matching

The call to asymmetric_key_hex_to_key_id() from ca_keys_setup()
silently fails with -ENOMEM.  Instead of dynamically allocating
memory from a __setup function, this patch defines a variable
and calls __asymmetric_key_hex_to_key_id(), a new helper function,
directly.

This bug was introduced by 'commit 46963b774d ("KEYS: Overhaul
key identification when searching for asymmetric keys")'.

Changelog:
- for clarification, rename hexlen to asciihexlen in
  asymmetric_key_hex_to_key_id()
- add size argument to __asymmetric_key_hex_to_key_id() - David Howells
- inline __asymmetric_key_hex_to_key_id() - David Howells
- remove duplicate strlen() calls

Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # 3.18

crypto/asymmetric_keys/asymmetric_keys.h

@@ -11,6 +11,9 @@
 
 extern struct asymmetric_key_id *asymmetric_key_hex_to_key_id(const char *id);
 
+extern int __asymmetric_key_hex_to_key_id(const char *id,
+					  struct asymmetric_key_id *match_id,
+					  size_t hexlen);
 static inline
 const struct asymmetric_key_ids *asymmetric_key_ids(const struct key *key)
 {

crypto/asymmetric_keys/asymmetric_type.c

@@ -104,6 +104,15 @@ static bool asymmetric_match_key_ids(
 	return false;
 }
 
+/* helper function can be called directly with pre-allocated memory */
+inline int __asymmetric_key_hex_to_key_id(const char *id,
+				   struct asymmetric_key_id *match_id,
+				   size_t hexlen)
+{
+	match_id->len = hexlen;
+	return hex2bin(match_id->data, id, hexlen);
+}
+
 /**
  * asymmetric_key_hex_to_key_id - Convert a hex string into a key ID.
  * @id: The ID as a hex string.
@@ -111,21 +120,20 @@ static bool asymmetric_match_key_ids(
 struct asymmetric_key_id *asymmetric_key_hex_to_key_id(const char *id)
 {
 	struct asymmetric_key_id *match_id;
-	size_t hexlen;
+	size_t asciihexlen;
 	int ret;
 
 	if (!*id)
 		return ERR_PTR(-EINVAL);
-	hexlen = strlen(id);
-	if (hexlen & 1)
+	asciihexlen = strlen(id);
+	if (asciihexlen & 1)
 		return ERR_PTR(-EINVAL);
 
-	match_id = kmalloc(sizeof(struct asymmetric_key_id) + hexlen / 2,
+	match_id = kmalloc(sizeof(struct asymmetric_key_id) + asciihexlen / 2,
 			   GFP_KERNEL);
 	if (!match_id)
 		return ERR_PTR(-ENOMEM);
-	match_id->len = hexlen / 2;
-	ret = hex2bin(match_id->data, id, hexlen / 2);
+	ret = __asymmetric_key_hex_to_key_id(id, match_id, asciihexlen / 2);
 	if (ret < 0) {
 		kfree(match_id);
 		return ERR_PTR(-EINVAL);

crypto/asymmetric_keys/x509_public_key.c

@@ -28,17 +28,30 @@ static bool use_builtin_keys;
 static struct asymmetric_key_id *ca_keyid;
 
 #ifndef MODULE
+static struct {
+	struct asymmetric_key_id id;
+	unsigned char data[10];
+} cakey;
+
 static int __init ca_keys_setup(char *str)
 {
 	if (!str)		/* default system keyring */
 		return 1;
 
 	if (strncmp(str, "id:", 3) == 0) {
-		struct asymmetric_key_id *p;
-		p = asymmetric_key_hex_to_key_id(str + 3);
-		if (p == ERR_PTR(-EINVAL))
-			pr_err("Unparsable hex string in ca_keys\n");
-		else if (!IS_ERR(p))
+		struct asymmetric_key_id *p = &cakey.id;
+		size_t hexlen = (strlen(str) - 3) / 2;
+		int ret;
+
+		if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
+			pr_err("Missing or invalid ca_keys id\n");
+			return 1;
+		}
+
+		ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
+		if (ret < 0)
+			pr_err("Unparsable ca_keys id hex string\n");
+		else
 			ca_keyid = p;	/* owner key 'id:xxxxxx' */
 	} else if (strcmp(str, "builtin") == 0) {
 		use_builtin_keys = true;