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 46963b774d44 ("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

1 files changed, 18 insertions, 5 deletions

diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index a6c42031628e..24f17e6c5904 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/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;