linux/fs/ecryptfs/miscdev.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 2008 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <[email protected]>
 */

#include <linux/fs.h>
#include <linux/hash.h>
#include <linux/random.h>
#include <linux/miscdevice.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/module.h>
#include "ecryptfs_kernel.h"

static atomic_t ecryptfs_num_miscdev_opens;

/**
 * ecryptfs_miscdev_poll
 * @file: dev file
 * @pt: dev poll table (ignored)
 *
 * Returns the poll mask
 */
static __poll_t
ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
{ … }

/**
 * ecryptfs_miscdev_open
 * @inode: inode of miscdev handle (ignored)
 * @file: file for miscdev handle
 *
 * Returns zero on success; non-zero otherwise
 */
static int
ecryptfs_miscdev_open(struct inode *inode, struct file *file)
{ … }

/**
 * ecryptfs_miscdev_release
 * @inode: inode of fs/ecryptfs/euid handle (ignored)
 * @file: file for fs/ecryptfs/euid handle
 *
 * This keeps the daemon registered until the daemon sends another
 * ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
 *
 * Returns zero on success; non-zero otherwise
 */
static int
ecryptfs_miscdev_release(struct inode *inode, struct file *file)
{ … }

/**
 * ecryptfs_send_miscdev
 * @data: Data to send to daemon; may be NULL
 * @data_size: Amount of data to send to daemon
 * @msg_ctx: Message context, which is used to handle the reply. If
 *           this is NULL, then we do not expect a reply.
 * @msg_type: Type of message
 * @msg_flags: Flags for message
 * @daemon: eCryptfs daemon object
 *
 * Add msg_ctx to queue and then, if it exists, notify the blocked
 * miscdevess about the data being available. Must be called with
 * ecryptfs_daemon_hash_mux held.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_send_miscdev(char *data, size_t data_size,
			  struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
			  u16 msg_flags, struct ecryptfs_daemon *daemon)
{ … }

/*
 * miscdevfs packet format:
 *  Octet 0: Type
 *  Octets 1-4: network byte order msg_ctx->counter
 *  Octets 5-N0: Size of struct ecryptfs_message to follow
 *  Octets N0-N1: struct ecryptfs_message (including data)
 *
 *  Octets 5-N1 not written if the packet type does not include a message
 */
#define PKT_TYPE_SIZE …
#define PKT_CTR_SIZE …
#define MIN_NON_MSG_PKT_SIZE …
#define MIN_MSG_PKT_SIZE …
/* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
#define MAX_MSG_PKT_SIZE …
#define PKT_TYPE_OFFSET …
#define PKT_CTR_OFFSET …
#define PKT_LEN_OFFSET …

/**
 * ecryptfs_miscdev_read - format and send message from queue
 * @file: miscdevfs handle
 * @buf: User buffer into which to copy the next message on the daemon queue
 * @count: Amount of space available in @buf
 * @ppos: Offset in file (ignored)
 *
 * Pulls the most recent message from the daemon queue, formats it for
 * being sent via a miscdevfs handle, and copies it into @buf
 *
 * Returns the number of bytes copied into the user buffer
 */
static ssize_t
ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
		      loff_t *ppos)
{ … }

/**
 * ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
 * @daemon: eCryptfs daemon object
 * @data: Bytes comprising struct ecryptfs_message
 * @data_size: sizeof(struct ecryptfs_message) + data len
 * @seq: Sequence number for miscdev response packet
 *
 * Returns zero on success; non-zero otherwise
 */
static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
				     size_t data_size, u32 seq)
{ … }

/**
 * ecryptfs_miscdev_write - handle write to daemon miscdev handle
 * @file: File for misc dev handle
 * @buf: Buffer containing user data
 * @count: Amount of data in @buf
 * @ppos: Pointer to offset in file (ignored)
 *
 * Returns the number of bytes read from @buf
 */
static ssize_t
ecryptfs_miscdev_write(struct file *file, const char __user *buf,
		       size_t count, loff_t *ppos)
{ … }


static const struct file_operations ecryptfs_miscdev_fops = …;

static struct miscdevice ecryptfs_miscdev = …;

/**
 * ecryptfs_init_ecryptfs_miscdev
 *
 * Messages sent to the userspace daemon from the kernel are placed on
 * a queue associated with the daemon. The next read against the
 * miscdev handle by that daemon will return the oldest message placed
 * on the message queue for the daemon.
 *
 * Returns zero on success; non-zero otherwise
 */
int __init ecryptfs_init_ecryptfs_miscdev(void)
{ … }

/**
 * ecryptfs_destroy_ecryptfs_miscdev
 *
 * All of the daemons must be exorcised prior to calling this
 * function.
 */
void ecryptfs_destroy_ecryptfs_miscdev(void)
{ … }