aio: remove unnecessary check

[linux-2.6/next.git] / fs / ecryptfs / messaging.c

/**
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 2004-2008 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
 *              Tyler Hicks <tyhicks@ou.edu>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */
#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 struct mutex ecryptfs_msg_ctx_lists_mux;

static struct hlist_head *ecryptfs_daemon_hash;
struct mutex ecryptfs_daemon_hash_mux;
static int ecryptfs_hash_bits;
#define ecryptfs_uid_hash(uid) \
        hash_long((unsigned long)uid, ecryptfs_hash_bits)

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)
{
        struct list_head *p;
        int rc;

        if (list_empty(&ecryptfs_msg_ctx_free_list)) {
                printk(KERN_WARNING "%s: The eCryptfs free "
                       "context list is empty.  It may be helpful to "
                       "specify the ecryptfs_message_buf_len "
                       "parameter to be greater than the current "
                       "value of [%d]\n", __func__, ecryptfs_message_buf_len);
                rc = -ENOMEM;
                goto out;
        }
        list_for_each(p, &ecryptfs_msg_ctx_free_list) {
                *msg_ctx = list_entry(p, struct ecryptfs_msg_ctx, node);
                if (mutex_trylock(&(*msg_ctx)->mux)) {
                        (*msg_ctx)->task = current;
                        rc = 0;
                        goto out;
                }
        }
        rc = -ENOMEM;
out:
        return rc;
}

/**
 * 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)
{
        list_move(&msg_ctx->node, &ecryptfs_msg_ctx_alloc_list);
        msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_PENDING;
        msg_ctx->counter = ++ecryptfs_msg_counter;
}

/**
 * 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)
{
        list_move(&(msg_ctx->node), &ecryptfs_msg_ctx_free_list);
        if (msg_ctx->msg)
                kfree(msg_ctx->msg);
        msg_ctx->msg = NULL;
        msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_FREE;
}

/**
 * ecryptfs_find_daemon_by_euid
 * @euid: The effective user id which maps to the desired daemon id
 * @user_ns: The namespace in which @euid applies
 * @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 given 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, uid_t euid,
                                 struct user_namespace *user_ns)
{
        struct hlist_node *elem;
        int rc;

        hlist_for_each_entry(*daemon, elem,
                             &ecryptfs_daemon_hash[ecryptfs_uid_hash(euid)],
                             euid_chain) {
                if ((*daemon)->euid == euid && (*daemon)->user_ns == user_ns) {
                        rc = 0;
                        goto out;
                }
        }
        rc = -EINVAL;
out:
        return rc;
}

/**
 * ecryptfs_spawn_daemon - Create and initialize a new daemon struct
 * @daemon: Pointer to set to newly allocated daemon struct
 * @euid: Effective user id for the daemon
 * @user_ns: The namespace in which @euid applies
 * @pid: Process id for the daemon
 *
 * 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, uid_t euid,
                      struct user_namespace *user_ns, struct pid *pid)
{
        int rc = 0;

        (*daemon) = kzalloc(sizeof(**daemon), GFP_KERNEL);
        if (!(*daemon)) {
                rc = -ENOMEM;
                printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
                       "GFP_KERNEL memory\n", __func__, sizeof(**daemon));
                goto out;
        }
        (*daemon)->euid = euid;
        (*daemon)->user_ns = get_user_ns(user_ns);
        (*daemon)->pid = get_pid(pid);
        (*daemon)->task = current;
        mutex_init(&(*daemon)->mux);
        INIT_LIST_HEAD(&(*daemon)->msg_ctx_out_queue);
        init_waitqueue_head(&(*daemon)->wait);
        (*daemon)->num_queued_msg_ctx = 0;
        hlist_add_head(&(*daemon)->euid_chain,
                       &ecryptfs_daemon_hash[ecryptfs_uid_hash(euid)]);
out:
        return rc;
}

/**
 * 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)
{
        struct ecryptfs_msg_ctx *msg_ctx, *msg_ctx_tmp;
        int rc = 0;

        mutex_lock(&daemon->mux);
        if ((daemon->flags & ECRYPTFS_DAEMON_IN_READ)
            || (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)) {
                rc = -EBUSY;
                printk(KERN_WARNING "%s: Attempt to destroy daemon with pid "
                       "[0x%p], but it is in the midst of a read or a poll\n",
                       __func__, daemon->pid);
                mutex_unlock(&daemon->mux);
                goto out;
        }
        list_for_each_entry_safe(msg_ctx, msg_ctx_tmp,
                                 &daemon->msg_ctx_out_queue, daemon_out_list) {
                list_del(&msg_ctx->daemon_out_list);
                daemon->num_queued_msg_ctx--;
                printk(KERN_WARNING "%s: Warning: dropping message that is in "
                       "the out queue of a dying daemon\n", __func__);
                ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
        }
        hlist_del(&daemon->euid_chain);
        if (daemon->task)
                wake_up_process(daemon->task);
        if (daemon->pid)
                put_pid(daemon->pid);
        if (daemon->user_ns)
                put_user_ns(daemon->user_ns);
        mutex_unlock(&daemon->mux);
        kzfree(daemon);
out:
        return rc;
}

/**
 * ecryptfs_process_quit
 * @euid: The user ID owner of the message
 * @user_ns: The namespace in which @euid applies
 * @pid: The process ID for the userspace program that sent the
 *       message
 *
 * Deletes the corresponding daemon for the given euid and pid, if
 * it is the registered that is requesting the deletion. Returns zero
 * after deleting the desired daemon; non-zero otherwise.
 */
int ecryptfs_process_quit(uid_t euid, struct user_namespace *user_ns,
                          struct pid *pid)
{
        struct ecryptfs_daemon *daemon;
        int rc;

        mutex_lock(&ecryptfs_daemon_hash_mux);
        rc = ecryptfs_find_daemon_by_euid(&daemon, euid, user_ns);
        if (rc || !daemon) {
                rc = -EINVAL;
                printk(KERN_ERR "Received request from user [%d] to "
                       "unregister unrecognized daemon [0x%p]\n", euid, pid);
                goto out_unlock;
        }
        rc = ecryptfs_exorcise_daemon(daemon);
out_unlock:
        mutex_unlock(&ecryptfs_daemon_hash_mux);
        return rc;
}

/**
 * ecryptfs_process_reponse
 * @msg: The ecryptfs message received; the caller should sanity check
 *       msg->data_len and free the memory
 * @pid: The process ID of the userspace application that sent the
 *       message
 * @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_message *msg, uid_t euid,
                              struct user_namespace *user_ns, struct pid *pid,
                              u32 seq)
{
        struct ecryptfs_daemon *uninitialized_var(daemon);
        struct ecryptfs_msg_ctx *msg_ctx;
        size_t msg_size;
        struct nsproxy *nsproxy;
        struct user_namespace *tsk_user_ns;
        uid_t ctx_euid;
        int rc;

        if (msg->index >= ecryptfs_message_buf_len) {
                rc = -EINVAL;
                printk(KERN_ERR "%s: Attempt to reference "
                       "context buffer at index [%d]; maximum "
                       "allowable is [%d]\n", __func__, msg->index,
                       (ecryptfs_message_buf_len - 1));
                goto out;
        }
        msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
        mutex_lock(&msg_ctx->mux);
        mutex_lock(&ecryptfs_daemon_hash_mux);
        rcu_read_lock();
        nsproxy = task_nsproxy(msg_ctx->task);
        if (nsproxy == NULL) {
                rc = -EBADMSG;
                printk(KERN_ERR "%s: Receiving process is a zombie. Dropping "
                       "message.\n", __func__);
                rcu_read_unlock();
                mutex_unlock(&ecryptfs_daemon_hash_mux);
                goto wake_up;
        }
        tsk_user_ns = __task_cred(msg_ctx->task)->user->user_ns;
        ctx_euid = task_euid(msg_ctx->task);
        rc = ecryptfs_find_daemon_by_euid(&daemon, ctx_euid, tsk_user_ns);
        rcu_read_unlock();
        mutex_unlock(&ecryptfs_daemon_hash_mux);
        if (rc) {
                rc = -EBADMSG;
                printk(KERN_WARNING "%s: User [%d] received a "
                       "message response from process [0x%p] but does "
                       "not have a registered daemon\n", __func__,
                       ctx_euid, pid);
                goto wake_up;
        }
        if (ctx_euid != euid) {
                rc = -EBADMSG;
                printk(KERN_WARNING "%s: Received message from user "
                       "[%d]; expected message from user [%d]\n", __func__,
                       euid, ctx_euid);
                goto unlock;
        }
        if (tsk_user_ns != user_ns) {
                rc = -EBADMSG;
                printk(KERN_WARNING "%s: Received message from user_ns "
                       "[0x%p]; expected message from user_ns [0x%p]\n",
                       __func__, user_ns, tsk_user_ns);
                goto unlock;
        }
        if (daemon->pid != pid) {
                rc = -EBADMSG;
                printk(KERN_ERR "%s: User [%d] sent a message response "
                       "from an unrecognized process [0x%p]\n",
                       __func__, ctx_euid, pid);
                goto unlock;
        }
        if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
                rc = -EINVAL;
                printk(KERN_WARNING "%s: Desired context element is not "
                       "pending a response\n", __func__);
                goto unlock;
        } else if (msg_ctx->counter != seq) {
                rc = -EINVAL;
                printk(KERN_WARNING "%s: Invalid message sequence; "
                       "expected [%d]; received [%d]\n", __func__,
                       msg_ctx->counter, seq);
                goto unlock;
        }
        msg_size = (sizeof(*msg) + msg->data_len);
        msg_ctx->msg = kmalloc(msg_size, GFP_KERNEL);
        if (!msg_ctx->msg) {
                rc = -ENOMEM;
                printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
                       "GFP_KERNEL memory\n", __func__, msg_size);
                goto unlock;
        }
        memcpy(msg_ctx->msg, msg, msg_size);
        msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
        rc = 0;
wake_up:
        wake_up_process(msg_ctx->task);
unlock:
        mutex_unlock(&msg_ctx->mux);
out:
        return rc;
}

/**
 * ecryptfs_send_message_locked
 * @data: The data to send
 * @data_len: The length of data
 * @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)
{
        struct ecryptfs_daemon *daemon;
        uid_t euid = current_euid();
        int rc;

        rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
        if (rc || !daemon) {
                rc = -ENOTCONN;
                printk(KERN_ERR "%s: User [%d] does not have a daemon "
                       "registered\n", __func__, euid);
                goto out;
        }
        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
        rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
        if (rc) {
                mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
                printk(KERN_WARNING "%s: Could not claim a free "
                       "context element\n", __func__);
                goto out;
        }
        ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
        mutex_unlock(&(*msg_ctx)->mux);
        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
        rc = ecryptfs_send_miscdev(data, data_len, *msg_ctx, msg_type, 0,
                                   daemon);
        if (rc)
                printk(KERN_ERR "%s: Error attempting to send message to "
                       "userspace daemon; rc = [%d]\n", __func__, rc);
out:
        return rc;
}

/**
 * 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)
{
        int rc;

        mutex_lock(&ecryptfs_daemon_hash_mux);
        rc = ecryptfs_send_message_locked(data, data_len, ECRYPTFS_MSG_REQUEST,
                                          msg_ctx);
        mutex_unlock(&ecryptfs_daemon_hash_mux);
        return rc;
}

/**
 * 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)
{
        signed long timeout = ecryptfs_message_wait_timeout * HZ;
        int rc = 0;

sleep:
        timeout = schedule_timeout_interruptible(timeout);
        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
        mutex_lock(&msg_ctx->mux);
        if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_DONE) {
                if (timeout) {
                        mutex_unlock(&msg_ctx->mux);
                        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
                        goto sleep;
                }
                rc = -ENOMSG;
        } else {
                *msg = msg_ctx->msg;
                msg_ctx->msg = NULL;
        }
        ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
        mutex_unlock(&msg_ctx->mux);
        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
        return rc;
}

int __init ecryptfs_init_messaging(void)
{
        int i;
        int rc = 0;

        if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
                ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
                printk(KERN_WARNING "%s: Specified number of users is "
                       "too large, defaulting to [%d] users\n", __func__,
                       ecryptfs_number_of_users);
        }
        mutex_init(&ecryptfs_daemon_hash_mux);
        mutex_lock(&ecryptfs_daemon_hash_mux);
        ecryptfs_hash_bits = 1;
        while (ecryptfs_number_of_users >> ecryptfs_hash_bits)
                ecryptfs_hash_bits++;
        ecryptfs_daemon_hash = kmalloc((sizeof(struct hlist_head)
                                        * (1 << ecryptfs_hash_bits)),
                                       GFP_KERNEL);
        if (!ecryptfs_daemon_hash) {
                rc = -ENOMEM;
                printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
                mutex_unlock(&ecryptfs_daemon_hash_mux);
                goto out;
        }
        for (i = 0; i < (1 << ecryptfs_hash_bits); i++)
                INIT_HLIST_HEAD(&ecryptfs_daemon_hash[i]);
        mutex_unlock(&ecryptfs_daemon_hash_mux);
        ecryptfs_msg_ctx_arr = kmalloc((sizeof(struct ecryptfs_msg_ctx)
                                        * ecryptfs_message_buf_len),
                                       GFP_KERNEL);
        if (!ecryptfs_msg_ctx_arr) {
                rc = -ENOMEM;
                printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
                goto out;
        }
        mutex_init(&ecryptfs_msg_ctx_lists_mux);
        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
        ecryptfs_msg_counter = 0;
        for (i = 0; i < ecryptfs_message_buf_len; i++) {
                INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].node);
                INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].daemon_out_list);
                mutex_init(&ecryptfs_msg_ctx_arr[i].mux);
                mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
                ecryptfs_msg_ctx_arr[i].index = i;
                ecryptfs_msg_ctx_arr[i].state = ECRYPTFS_MSG_CTX_STATE_FREE;
                ecryptfs_msg_ctx_arr[i].counter = 0;
                ecryptfs_msg_ctx_arr[i].task = NULL;
                ecryptfs_msg_ctx_arr[i].msg = NULL;
                list_add_tail(&ecryptfs_msg_ctx_arr[i].node,
                              &ecryptfs_msg_ctx_free_list);
                mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
        }
        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
        rc = ecryptfs_init_ecryptfs_miscdev();
        if (rc)
                ecryptfs_release_messaging();
out:
        return rc;
}

void ecryptfs_release_messaging(void)
{
        if (ecryptfs_msg_ctx_arr) {
                int i;

                mutex_lock(&ecryptfs_msg_ctx_lists_mux);
                for (i = 0; i < ecryptfs_message_buf_len; i++) {
                        mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
                        if (ecryptfs_msg_ctx_arr[i].msg)
                                kfree(ecryptfs_msg_ctx_arr[i].msg);
                        mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
                }
                kfree(ecryptfs_msg_ctx_arr);
                mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
        }
        if (ecryptfs_daemon_hash) {
                struct hlist_node *elem;
                struct ecryptfs_daemon *daemon;
                int i;

                mutex_lock(&ecryptfs_daemon_hash_mux);
                for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
                        int rc;

                        hlist_for_each_entry(daemon, elem,
                                             &ecryptfs_daemon_hash[i],
                                             euid_chain) {
                                rc = ecryptfs_exorcise_daemon(daemon);
                                if (rc)
                                        printk(KERN_ERR "%s: Error whilst "
                                               "attempting to destroy daemon; "
                                               "rc = [%d]. Dazed and confused, "
                                               "but trying to continue.\n",
                                               __func__, rc);
                        }
                }
                kfree(ecryptfs_daemon_hash);
                mutex_unlock(&ecryptfs_daemon_hash_mux);
        }
        ecryptfs_destroy_ecryptfs_miscdev();
        return;
}