SMACK: Fix the memory leak in smack_cred_prepare() hook

Memory leak in smack_cred_prepare()function.
smack_cred_prepare() hook returns error if there is error in allocating
memory in smk_copy_rules() or smk_copy_relabel() function.
If smack_cred_prepare() function returns error then the calling
function should call smack_cred_free() function for cleanup.
In smack_cred_free() function first credential is  extracted and
then all rules are deleted. In smack_cred_prepare() function security
field is assigned in the end when all function return success. But this
function may return before and memory will not be freed.
Signed-off-by: NHimanshu Shukla <himanshu.sh@samsung.com>
Acked-by: NCasey Schaufler <casey@schaufler-ca.com>

security/smack/smack_lsm.c

@@ -2023,6 +2023,8 @@ static int smack_cred_prepare(struct cred *new, const struct cred *old,
 	if (new_tsp == NULL)
 		return -ENOMEM;
 
+	new->security = new_tsp;
+
 	rc = smk_copy_rules(&new_tsp->smk_rules, &old_tsp->smk_rules, gfp);
 	if (rc != 0)
 		return rc;
@@ -2032,7 +2034,6 @@ static int smack_cred_prepare(struct cred *new, const struct cred *old,
 	if (rc != 0)
 		return rc;
 
-	new->security = new_tsp;
 	return 0;
 }