afs: Fix a use after free in afs_xattr_get_acl()

The "op" pointer is freed earlier when we call afs_put_operation().

Fixes: e49c7b2 ("afs: Build an abstraction around an "operation" concept")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Colin Ian King <colin.king@canonical.com>

fs/afs/xattr.c

@@ -85,7 +85,7 @@ static int afs_xattr_get_acl(const struct xattr_handler *handler,
 			if (acl->size <= size)
 				memcpy(buffer, acl->data, acl->size);
 			else
-				op->error = -ERANGE;
+				ret = -ERANGE;
 		}
 	}