fscrypto: lock inode while setting encryption policy

commit 8906a822 upstream.

i_rwsem needs to be acquired while setting an encryption policy so that
concurrent calls to FS_IOC_SET_ENCRYPTION_POLICY are correctly
serialized (especially the ->get_context() + ->set_context() pair), and
so that new files cannot be created in the directory during or after the
->empty_dir() check.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Richard Weinberger <richard@nod.at>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/ext4/ioctl.c

@@ -633,8 +633,12 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		if (err)
 			goto encryption_policy_out;
 
+		mutex_lock(&inode->i_mutex);
+
 		err = ext4_process_policy(&policy, inode);
 
+		mutex_unlock(&inode->i_mutex);
+
 		mnt_drop_write_file(filp);
 encryption_policy_out:
 		return err;

fs/f2fs/file.c

@@ -1535,12 +1535,19 @@ static int f2fs_ioc_set_encryption_policy(struct file *filp, unsigned long arg)
 #ifdef CONFIG_F2FS_FS_ENCRYPTION
 	struct f2fs_encryption_policy policy;
 	struct inode *inode = file_inode(filp);
+	int err;
 
 	if (copy_from_user(&policy, (struct f2fs_encryption_policy __user *)arg,
 				sizeof(policy)))
 		return -EFAULT;
 
-	return f2fs_process_policy(&policy, inode);
+	mutex_lock(&inode->i_mutex);
+
+	err = f2fs_process_policy(&policy, inode);
+
+	mutex_unlock(&inode->i_mutex);
+
+	return err;
 #else
 	return -EOPNOTSUPP;
 #endif