ima: Fix memory leak in __ima_inode_hash()

Commit f3cc6b25 ("ima: always measure and audit files in policy") lets
measurement or audit happen even if the file digest cannot be calculated.

As a result, iint->ima_hash could have been allocated despite
ima_collect_measurement() returning an error.

Since ima_hash belongs to a temporary inode metadata structure, declared
at the beginning of __ima_inode_hash(), just add a kfree() call if
ima_collect_measurement() returns an error different from -ENOMEM (in that
case, ima_hash should not have been allocated).

Cc: stable@vger.kernel.org
Fixes: 280fe836 ("ima: Always return a file measurement in ima_file_hash()")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

security/integrity/ima/ima_main.c

@@ -542,8 +542,13 @@ static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf,
 
 		rc = ima_collect_measurement(&tmp_iint, file, NULL, 0,
 					     ima_hash_algo, NULL);
-		if (rc < 0)
+		if (rc < 0) {
+			/* ima_hash could be allocated in case of failure. */
+			if (rc != -ENOMEM)
+				kfree(tmp_iint.ima_hash);
+
 			return -EOPNOTSUPP;
+		}
 
 		iint = &tmp_iint;
 		mutex_lock(&iint->mutex);