[JFFS2] Check for all-zero node headers

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

/**
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 2004-2006 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 "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_id_hash;
static struct mutex ecryptfs_daemon_id_hash_mux;
static int ecryptfs_hash_buckets;
#define ecryptfs_uid_hash(uid) \
        hash_long((unsigned long)uid, ecryptfs_hash_buckets)

static unsigned int 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.  Returns zero on success; non-zero on error or upon
 * failure to acquire a free context element.  Be sure to lock the
 * list mutex before calling.
 */
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)) {
                ecryptfs_printk(KERN_WARNING, "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", 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
 *
 * Be sure to lock the list mutex and the context mutex before
 * calling.
 */
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
 *
 * Be sure to lock the list mutex and the context mutex before
 * calling.
 */
static 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->state = ECRYPTFS_MSG_CTX_STATE_FREE;
}

/**
 * ecryptfs_find_daemon_id
 * @uid: The user id which maps to the desired daemon id
 * @id: If return value is zero, points to the desired daemon id
 *      pointer
 *
 * Search the hash list for the given user id.  Returns zero if the
 * user id exists in the list; non-zero otherwise.  The daemon id hash
 * mutex should be held before calling this function.
 */
static int ecryptfs_find_daemon_id(uid_t uid, struct ecryptfs_daemon_id **id)
{
        struct hlist_node *elem;
        int rc;

        hlist_for_each_entry(*id, elem,
                             &ecryptfs_daemon_id_hash[ecryptfs_uid_hash(uid)],
                             id_chain) {
                if ((*id)->uid == uid) {
                        rc = 0;
                        goto out;
                }
        }
        rc = -EINVAL;
out:
        return rc;
}

static int ecryptfs_send_raw_message(unsigned int transport, u16 msg_type,
                                     pid_t pid)
{
        int rc;

        switch(transport) {
        case ECRYPTFS_TRANSPORT_NETLINK:
                rc = ecryptfs_send_netlink(NULL, 0, NULL, msg_type, 0, pid);
                break;
        case ECRYPTFS_TRANSPORT_CONNECTOR:
        case ECRYPTFS_TRANSPORT_RELAYFS:
        default:
                rc = -ENOSYS;
        }
        return rc;
}

/**
 * ecryptfs_process_helo
 * @transport: The underlying transport (netlink, etc.)
 * @uid: The user ID owner of the message
 * @pid: The process ID for the userspace program that sent the
 *       message
 *
 * Adds the uid and pid values to the daemon id hash.  If a uid
 * already has a daemon pid registered, the daemon will be
 * unregistered before the new daemon id is put into the hash list.
 * Returns zero after adding a new daemon id to the hash list;
 * non-zero otherwise.
 */
int ecryptfs_process_helo(unsigned int transport, uid_t uid, pid_t pid)
{
        struct ecryptfs_daemon_id *new_id;
        struct ecryptfs_daemon_id *old_id;
        int rc;

        mutex_lock(&ecryptfs_daemon_id_hash_mux);
        new_id = kmalloc(sizeof(*new_id), GFP_KERNEL);
        if (!new_id) {
                rc = -ENOMEM;
                ecryptfs_printk(KERN_ERR, "Failed to allocate memory; unable "
                                "to register daemon [%d] for user [%d]\n",
                                pid, uid);
                goto unlock;
        }
        if (!ecryptfs_find_daemon_id(uid, &old_id)) {
                printk(KERN_WARNING "Received request from user [%d] "
                       "to register daemon [%d]; unregistering daemon "
                       "[%d]\n", uid, pid, old_id->pid);
                hlist_del(&old_id->id_chain);
                rc = ecryptfs_send_raw_message(transport, ECRYPTFS_NLMSG_QUIT,
                                               old_id->pid);
                if (rc)
                        printk(KERN_WARNING "Failed to send QUIT "
                               "message to daemon [%d]; rc = [%d]\n",
                               old_id->pid, rc);
                kfree(old_id);
        }
        new_id->uid = uid;
        new_id->pid = pid;
        hlist_add_head(&new_id->id_chain,
                       &ecryptfs_daemon_id_hash[ecryptfs_uid_hash(uid)]);
        rc = 0;
unlock:
        mutex_unlock(&ecryptfs_daemon_id_hash_mux);
        return rc;
}

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

        mutex_lock(&ecryptfs_daemon_id_hash_mux);
        if (ecryptfs_find_daemon_id(uid, &id)) {
                rc = -EINVAL;
                ecryptfs_printk(KERN_ERR, "Received request from user [%d] to "
                                "unregister unrecognized daemon [%d]\n", uid,
                                pid);
                goto unlock;
        }
        if (id->pid != pid) {
                rc = -EINVAL;
                ecryptfs_printk(KERN_WARNING, "Received request from user [%d] "
                                "with pid [%d] to unregister daemon [%d]\n",
                                uid, pid, id->pid);
                goto unlock;
        }
        hlist_del(&id->id_chain);
        kfree(id);
        rc = 0;
unlock:
        mutex_unlock(&ecryptfs_daemon_id_hash_mux);
        return rc;
}

/**
 * ecryptfs_process_reponse
 * @msg: The ecryptfs message received; the caller should sanity check
 *       msg->data_len
 * @pid: The process ID of the userspace application that sent the
 *       message
 * @seq: The sequence number of the message
 *
 * Processes a response message after sending a operation request to
 * userspace. Returns zero upon delivery to desired context element;
 * non-zero upon delivery failure or error.
 */
int ecryptfs_process_response(struct ecryptfs_message *msg, uid_t uid,
                              pid_t pid, u32 seq)
{
        struct ecryptfs_daemon_id *id;
        struct ecryptfs_msg_ctx *msg_ctx;
        int msg_size;
        int rc;

        if (msg->index >= ecryptfs_message_buf_len) {
                rc = -EINVAL;
                ecryptfs_printk(KERN_ERR, "Attempt to reference "
                                "context buffer at index [%d]; maximum "
                                "allowable is [%d]\n", msg->index,
                                (ecryptfs_message_buf_len - 1));
                goto out;
        }
        msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
        mutex_lock(&msg_ctx->mux);
        if (ecryptfs_find_daemon_id(msg_ctx->task->euid, &id)) {
                rc = -EBADMSG;
                ecryptfs_printk(KERN_WARNING, "User [%d] received a "
                                "message response from process [%d] but does "
                                "not have a registered daemon\n",
                                msg_ctx->task->euid, pid);
                goto wake_up;
        }
        if (msg_ctx->task->euid != uid) {
                rc = -EBADMSG;
                ecryptfs_printk(KERN_WARNING, "Received message from user "
                                "[%d]; expected message from user [%d]\n",
                                uid, msg_ctx->task->euid);
                goto unlock;
        }
        if (id->pid != pid) {
                rc = -EBADMSG;
                ecryptfs_printk(KERN_ERR, "User [%d] received a "
                                "message response from an unrecognized "
                                "process [%d]\n", msg_ctx->task->euid, pid);
                goto unlock;
        }
        if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
                rc = -EINVAL;
                ecryptfs_printk(KERN_WARNING, "Desired context element is not "
                                "pending a response\n");
                goto unlock;
        } else if (msg_ctx->counter != seq) {
                rc = -EINVAL;
                ecryptfs_printk(KERN_WARNING, "Invalid message sequence; "
                                "expected [%d]; received [%d]\n",
                                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;
                ecryptfs_printk(KERN_ERR, "Failed to allocate memory\n");
                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
 * @transport: The transport over which to send the message (i.e.,
 *             netlink)
 * @data: The data to send
 * @data_len: The length of data
 * @msg_ctx: The message context allocated for the send
 */
int ecryptfs_send_message(unsigned int transport, char *data, int data_len,
                          struct ecryptfs_msg_ctx **msg_ctx)
{
        struct ecryptfs_daemon_id *id;
        int rc;

        mutex_lock(&ecryptfs_daemon_id_hash_mux);
        if (ecryptfs_find_daemon_id(current->euid, &id)) {
                mutex_unlock(&ecryptfs_daemon_id_hash_mux);
                rc = -ENOTCONN;
                ecryptfs_printk(KERN_ERR, "User [%d] does not have a daemon "
                                "registered\n", current->euid);
                goto out;
        }
        mutex_unlock(&ecryptfs_daemon_id_hash_mux);
        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
        rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
        if (rc) {
                mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
                ecryptfs_printk(KERN_WARNING, "Could not claim a free "
                                "context element\n");
                goto out;
        }
        ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
        mutex_unlock(&(*msg_ctx)->mux);
        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
        switch (transport) {
        case ECRYPTFS_TRANSPORT_NETLINK:
                rc = ecryptfs_send_netlink(data, data_len, *msg_ctx,
                                           ECRYPTFS_NLMSG_REQUEST, 0, id->pid);
                break;
        case ECRYPTFS_TRANSPORT_CONNECTOR:
        case ECRYPTFS_TRANSPORT_RELAYFS:
        default:
                rc = -ENOSYS;
        }
        if (rc) {
                printk(KERN_ERR "Error attempting to send message to userspace "
                       "daemon; rc = [%d]\n", rc);
        }
out:
        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.
 */
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 ecryptfs_init_messaging(unsigned int transport)
{
        int i;
        int rc = 0;

        if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
                ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
                ecryptfs_printk(KERN_WARNING, "Specified number of users is "
                                "too large, defaulting to [%d] users\n",
                                ecryptfs_number_of_users);
        }
        mutex_init(&ecryptfs_daemon_id_hash_mux);
        mutex_lock(&ecryptfs_daemon_id_hash_mux);
        ecryptfs_hash_buckets = 0;
        while (ecryptfs_number_of_users >> ++ecryptfs_hash_buckets);
        ecryptfs_daemon_id_hash = kmalloc(sizeof(struct hlist_head)
                                          * ecryptfs_hash_buckets, GFP_KERNEL);
        if (!ecryptfs_daemon_id_hash) {
                rc = -ENOMEM;
                ecryptfs_printk(KERN_ERR, "Failed to allocate memory\n");
                goto out;
        }
        for (i = 0; i < ecryptfs_hash_buckets; i++)
                INIT_HLIST_HEAD(&ecryptfs_daemon_id_hash[i]);
        mutex_unlock(&ecryptfs_daemon_id_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;
                ecryptfs_printk(KERN_ERR, "Failed to allocate memory\n");
                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);
                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);
        switch(transport) {
        case ECRYPTFS_TRANSPORT_NETLINK:
                rc = ecryptfs_init_netlink();
                if (rc)
                        ecryptfs_release_messaging(transport);
                break;
        case ECRYPTFS_TRANSPORT_CONNECTOR:
        case ECRYPTFS_TRANSPORT_RELAYFS:
        default:
                rc = -ENOSYS;
        }
out:
        return rc;
}

void ecryptfs_release_messaging(unsigned int transport)
{
        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_id_hash) {
                struct hlist_node *elem;
                struct ecryptfs_daemon_id *id;
                int i;

                mutex_lock(&ecryptfs_daemon_id_hash_mux);
                for (i = 0; i < ecryptfs_hash_buckets; i++) {
                        hlist_for_each_entry(id, elem,
                                             &ecryptfs_daemon_id_hash[i],
                                             id_chain) {
                                hlist_del(elem);
                                kfree(id);
                        }
                }
                kfree(ecryptfs_daemon_id_hash);
                mutex_unlock(&ecryptfs_daemon_id_hash_mux);
        }
        switch(transport) {
        case ECRYPTFS_TRANSPORT_NETLINK:
                ecryptfs_release_netlink();
                break;
        case ECRYPTFS_TRANSPORT_CONNECTOR:
        case ECRYPTFS_TRANSPORT_RELAYFS:
        default:
                break;
        }
        return;
}