ext4 crypto: handle unexpected lack of encryption keys

Fix up attempts by users to try to write to a file when they don't
have access to the encryption key.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 875ca6b..ac517f1 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -226,6 +226,8 @@
 		int err = ext4_get_encryption_info(inode);
 		if (err)
 			return 0;
+		if (ext4_encryption_info(inode) == NULL)
+			return -ENOKEY;
 	}
 	file_accessed(file);
 	if (IS_DAX(file_inode(file))) {
@@ -278,6 +280,13 @@
 			ext4_journal_stop(handle);
 		}
 	}
+	if (ext4_encrypted_inode(inode)) {
+		ret = ext4_get_encryption_info(inode);
+		if (ret)
+			return -EACCES;
+		if (ext4_encryption_info(inode) == NULL)
+			return -ENOKEY;
+	}
 	/*
 	 * Set up the jbd2_inode if we are opening the inode for
 	 * writing and the journal is present
@@ -287,13 +296,7 @@
 		if (ret < 0)
 			return ret;
 	}
-	ret = dquot_file_open(inode, filp);
-	if (!ret && ext4_encrypted_inode(inode)) {
-		ret = ext4_get_encryption_info(inode);
-		if (ret)
-			ret = -EACCES;
-	}
-	return ret;
+	return dquot_file_open(inode, filp);
 }
 
 /*