ima: fix memory leak in ima_release_policy

When the "policy" securityfs file is opened for read, it is opened as a
sequential file. However, when it is eventually released, there is no
cleanup for the sequential file, therefore some memory is leaked.

This patch adds a call to seq_release() in ima_release_policy() to clean up
the memory when the file is opened for read.

Fixes: 80eae209 IMA: allow reading back the current policy
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Eric Richter <erichte@linux.vnet.ibm.com>
Tested-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

security/integrity/ima/ima_fs.c

@@ -401,7 +401,7 @@ static int ima_release_policy(struct inode *inode, struct file *file)
 	const char *cause = valid_policy ? "completed" : "failed";
 
 	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
-		return 0;
+		return seq_release(inode, file);
 
 	if (valid_policy && ima_check_policy() < 0) {
 		cause = "failed";