linux/fs/ecryptfs/messaging.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 2004-2008 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <[email protected]>
 *		Tyler Hicks <[email protected]>
 */
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/user_namespace.h>
#include <linux/nsproxy.h>
#include "ecryptfs_kernel.h"

static LIST_HEAD(ecryptfs_msg_ctx_free_list);
static LIST_HEAD(ecryptfs_msg_ctx_alloc_list);
static DEFINE_MUTEX(ecryptfs_msg_ctx_lists_mux);

static struct hlist_head *ecryptfs_daemon_hash;
DEFINE_MUTEX(…) …;
static int ecryptfs_hash_bits;
#define ecryptfs_current_euid_hash(uid) …

static u32 ecryptfs_msg_counter;
static struct ecryptfs_msg_ctx *ecryptfs_msg_ctx_arr;

/**
 * ecryptfs_acquire_free_msg_ctx
 * @msg_ctx: The context that was acquired from the free list
 *
 * Acquires a context element from the free list and locks the mutex
 * on the context.  Sets the msg_ctx task to current.  Returns zero on
 * success; non-zero on error or upon failure to acquire a free
 * context element.  Must be called with ecryptfs_msg_ctx_lists_mux
 * held.
 */
static int ecryptfs_acquire_free_msg_ctx(struct ecryptfs_msg_ctx **msg_ctx)
{ … }

/**
 * ecryptfs_msg_ctx_free_to_alloc
 * @msg_ctx: The context to move from the free list to the alloc list
 *
 * Must be called with ecryptfs_msg_ctx_lists_mux held.
 */
static void ecryptfs_msg_ctx_free_to_alloc(struct ecryptfs_msg_ctx *msg_ctx)
{ … }

/**
 * ecryptfs_msg_ctx_alloc_to_free
 * @msg_ctx: The context to move from the alloc list to the free list
 *
 * Must be called with ecryptfs_msg_ctx_lists_mux held.
 */
void ecryptfs_msg_ctx_alloc_to_free(struct ecryptfs_msg_ctx *msg_ctx)
{ … }

/**
 * ecryptfs_find_daemon_by_euid
 * @daemon: If return value is zero, points to the desired daemon pointer
 *
 * Must be called with ecryptfs_daemon_hash_mux held.
 *
 * Search the hash list for the current effective user id.
 *
 * Returns zero if the user id exists in the list; non-zero otherwise.
 */
int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon)
{ … }

/**
 * ecryptfs_spawn_daemon - Create and initialize a new daemon struct
 * @daemon: Pointer to set to newly allocated daemon struct
 * @file: File used when opening /dev/ecryptfs
 *
 * Must be called ceremoniously while in possession of
 * ecryptfs_sacred_daemon_hash_mux
 *
 * Returns zero on success; non-zero otherwise
 */
int
ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, struct file *file)
{ … }

/*
 * ecryptfs_exorcise_daemon - Destroy the daemon struct
 *
 * Must be called ceremoniously while in possession of
 * ecryptfs_daemon_hash_mux and the daemon's own mux.
 */
int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
{ … }

/**
 * ecryptfs_process_response
 * @daemon: eCryptfs daemon object
 * @msg: The ecryptfs message received; the caller should sanity check
 *       msg->data_len and free the memory
 * @seq: The sequence number of the message; must match the sequence
 *       number for the existing message context waiting for this
 *       response
 *
 * Processes a response message after sending an operation request to
 * userspace. Some other process is awaiting this response. Before
 * sending out its first communications, the other process allocated a
 * msg_ctx from the ecryptfs_msg_ctx_arr at a particular index. The
 * response message contains this index so that we can copy over the
 * response message into the msg_ctx that the process holds a
 * reference to. The other process is going to wake up, check to see
 * that msg_ctx->state == ECRYPTFS_MSG_CTX_STATE_DONE, and then
 * proceed to read off and process the response message. Returns zero
 * upon delivery to desired context element; non-zero upon delivery
 * failure or error.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
			      struct ecryptfs_message *msg, u32 seq)
{ … }

/**
 * ecryptfs_send_message_locked
 * @data: The data to send
 * @data_len: The length of data
 * @msg_type: Type of message
 * @msg_ctx: The message context allocated for the send
 *
 * Must be called with ecryptfs_daemon_hash_mux held.
 *
 * Returns zero on success; non-zero otherwise
 */
static int
ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
			     struct ecryptfs_msg_ctx **msg_ctx)
{ … }

/**
 * ecryptfs_send_message
 * @data: The data to send
 * @data_len: The length of data
 * @msg_ctx: The message context allocated for the send
 *
 * Grabs ecryptfs_daemon_hash_mux.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_send_message(char *data, int data_len,
			  struct ecryptfs_msg_ctx **msg_ctx)
{ … }

/**
 * ecryptfs_wait_for_response
 * @msg_ctx: The context that was assigned when sending a message
 * @msg: The incoming message from userspace; not set if rc != 0
 *
 * Sleeps until awaken by ecryptfs_receive_message or until the amount
 * of time exceeds ecryptfs_message_wait_timeout.  If zero is
 * returned, msg will point to a valid message from userspace; a
 * non-zero value is returned upon failure to receive a message or an
 * error occurs. Callee must free @msg on success.
 */
int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
			       struct ecryptfs_message **msg)
{ … }

int __init ecryptfs_init_messaging(void)
{ … }

void ecryptfs_release_messaging(void)
{ … }