eCryptfs: Sanitize write counts of /dev/ecryptfs

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / ecryptfs / miscdev.c

/**
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 2008 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
 *
 * 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/fs.h>
#include <linux/hash.h>
#include <linux/random.h>
#include <linux/miscdevice.h>
#include <linux/poll.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 (ignored)
 * @pt: dev poll table (ignored)
 *
 * Returns the poll mask
 */
static unsigned int
ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
{
        struct ecryptfs_daemon *daemon;
        unsigned int mask = 0;
        uid_t euid = current_euid();
        int rc;

        mutex_lock(&ecryptfs_daemon_hash_mux);
        /* TODO: Just use file->private_data? */
        rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
        BUG_ON(rc || !daemon);
        mutex_lock(&daemon->mux);
        mutex_unlock(&ecryptfs_daemon_hash_mux);
        if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
                printk(KERN_WARNING "%s: Attempt to poll on zombified "
                       "daemon\n", __func__);
                goto out_unlock_daemon;
        }
        if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
                goto out_unlock_daemon;
        if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
                goto out_unlock_daemon;
        daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
        mutex_unlock(&daemon->mux);
        poll_wait(file, &daemon->wait, pt);
        mutex_lock(&daemon->mux);
        if (!list_empty(&daemon->msg_ctx_out_queue))
                mask |= POLLIN | POLLRDNORM;
out_unlock_daemon:
        daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
        mutex_unlock(&daemon->mux);
        return mask;
}

/**
 * ecryptfs_miscdev_open
 * @inode: inode of miscdev handle (ignored)
 * @file: file for miscdev handle (ignored)
 *
 * Returns zero on success; non-zero otherwise
 */
static int
ecryptfs_miscdev_open(struct inode *inode, struct file *file)
{
        struct ecryptfs_daemon *daemon = NULL;
        uid_t euid = current_euid();
        int rc;

        mutex_lock(&ecryptfs_daemon_hash_mux);
        rc = try_module_get(THIS_MODULE);
        if (rc == 0) {
                rc = -EIO;
                printk(KERN_ERR "%s: Error attempting to increment module use "
                       "count; rc = [%d]\n", __func__, rc);
                goto out_unlock_daemon_list;
        }
        rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
        if (rc || !daemon) {
                rc = ecryptfs_spawn_daemon(&daemon, euid, current_user_ns(),
                                           task_pid(current));
                if (rc) {
                        printk(KERN_ERR "%s: Error attempting to spawn daemon; "
                               "rc = [%d]\n", __func__, rc);
                        goto out_module_put_unlock_daemon_list;
                }
        }
        mutex_lock(&daemon->mux);
        if (daemon->pid != task_pid(current)) {
                rc = -EINVAL;
                printk(KERN_ERR "%s: pid [0x%p] has registered with euid [%d], "
                       "but pid [0x%p] has attempted to open the handle "
                       "instead\n", __func__, daemon->pid, daemon->euid,
                       task_pid(current));
                goto out_unlock_daemon;
        }
        if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
                rc = -EBUSY;
                printk(KERN_ERR "%s: Miscellaneous device handle may only be "
                       "opened once per daemon; pid [0x%p] already has this "
                       "handle open\n", __func__, daemon->pid);
                goto out_unlock_daemon;
        }
        daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
        atomic_inc(&ecryptfs_num_miscdev_opens);
out_unlock_daemon:
        mutex_unlock(&daemon->mux);
out_module_put_unlock_daemon_list:
        if (rc)
                module_put(THIS_MODULE);
out_unlock_daemon_list:
        mutex_unlock(&ecryptfs_daemon_hash_mux);
        return rc;
}

/**
 * ecryptfs_miscdev_release
 * @inode: inode of fs/ecryptfs/euid handle (ignored)
 * @file: file for fs/ecryptfs/euid handle (ignored)
 *
 * 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)
{
        struct ecryptfs_daemon *daemon = NULL;
        uid_t euid = current_euid();
        int rc;

        mutex_lock(&ecryptfs_daemon_hash_mux);
        rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
        BUG_ON(rc || !daemon);
        mutex_lock(&daemon->mux);
        BUG_ON(daemon->pid != task_pid(current));
        BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
        daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
        atomic_dec(&ecryptfs_num_miscdev_opens);
        mutex_unlock(&daemon->mux);
        rc = ecryptfs_exorcise_daemon(daemon);
        if (rc) {
                printk(KERN_CRIT "%s: Fatal error whilst attempting to "
                       "shut down daemon; rc = [%d]. Please report this "
                       "bug.\n", __func__, rc);
                BUG();
        }
        module_put(THIS_MODULE);
        mutex_unlock(&ecryptfs_daemon_hash_mux);
        return rc;
}

/**
 * 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)
{
        int rc = 0;

        mutex_lock(&msg_ctx->mux);
        msg_ctx->msg = kmalloc((sizeof(*msg_ctx->msg) + data_size),
                               GFP_KERNEL);
        if (!msg_ctx->msg) {
                rc = -ENOMEM;
                printk(KERN_ERR "%s: Out of memory whilst attempting "
                       "to kmalloc(%zd, GFP_KERNEL)\n", __func__,
                       (sizeof(*msg_ctx->msg) + data_size));
                goto out_unlock;
        }
        msg_ctx->msg->index = msg_ctx->index;
        msg_ctx->msg->data_len = data_size;
        msg_ctx->type = msg_type;
        memcpy(msg_ctx->msg->data, data, data_size);
        msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
        mutex_lock(&daemon->mux);
        list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
        daemon->num_queued_msg_ctx++;
        wake_up_interruptible(&daemon->wait);
        mutex_unlock(&daemon->mux);
out_unlock:
        mutex_unlock(&msg_ctx->mux);
        return rc;
}

/**
 * ecryptfs_miscdev_read - format and send message from queue
 * @file: fs/ecryptfs/euid miscdevfs handle (ignored)
 * @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)
{
        struct ecryptfs_daemon *daemon;
        struct ecryptfs_msg_ctx *msg_ctx;
        size_t packet_length_size;
        char packet_length[3];
        size_t i;
        size_t total_length;
        uid_t euid = current_euid();
        int rc;

        mutex_lock(&ecryptfs_daemon_hash_mux);
        /* TODO: Just use file->private_data? */
        rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
        BUG_ON(rc || !daemon);
        mutex_lock(&daemon->mux);
        if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
                rc = 0;
                mutex_unlock(&ecryptfs_daemon_hash_mux);
                printk(KERN_WARNING "%s: Attempt to read from zombified "
                       "daemon\n", __func__);
                goto out_unlock_daemon;
        }
        if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
                rc = 0;
                mutex_unlock(&ecryptfs_daemon_hash_mux);
                goto out_unlock_daemon;
        }
        /* This daemon will not go away so long as this flag is set */
        daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
        mutex_unlock(&ecryptfs_daemon_hash_mux);
check_list:
        if (list_empty(&daemon->msg_ctx_out_queue)) {
                mutex_unlock(&daemon->mux);
                rc = wait_event_interruptible(
                        daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
                mutex_lock(&daemon->mux);
                if (rc < 0) {
                        rc = 0;
                        goto out_unlock_daemon;
                }
        }
        if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
                rc = 0;
                goto out_unlock_daemon;
        }
        if (list_empty(&daemon->msg_ctx_out_queue)) {
                /* Something else jumped in since the
                 * wait_event_interruptable() and removed the
                 * message from the queue; try again */
                goto check_list;
        }
        BUG_ON(euid != daemon->euid);
        BUG_ON(current_user_ns() != daemon->user_ns);
        BUG_ON(task_pid(current) != daemon->pid);
        msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
                                   struct ecryptfs_msg_ctx, daemon_out_list);
        BUG_ON(!msg_ctx);
        mutex_lock(&msg_ctx->mux);
        if (msg_ctx->msg) {
                rc = ecryptfs_write_packet_length(packet_length,
                                                  msg_ctx->msg_size,
                                                  &packet_length_size);
                if (rc) {
                        rc = 0;
                        printk(KERN_WARNING "%s: Error writing packet length; "
                               "rc = [%d]\n", __func__, rc);
                        goto out_unlock_msg_ctx;
                }
        } else {
                packet_length_size = 0;
                msg_ctx->msg_size = 0;
        }
        /* 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 */
        total_length = (1 + 4 + packet_length_size + msg_ctx->msg_size);
        if (count < total_length) {
                rc = 0;
                printk(KERN_WARNING "%s: Only given user buffer of "
                       "size [%zd], but we need [%zd] to read the "
                       "pending message\n", __func__, count, total_length);
                goto out_unlock_msg_ctx;
        }
        rc = -EFAULT;
        if (put_user(msg_ctx->type, buf))
                goto out_unlock_msg_ctx;
        if (put_user(cpu_to_be32(msg_ctx->counter), (__be32 __user *)(buf + 1)))
                goto out_unlock_msg_ctx;
        i = 5;
        if (msg_ctx->msg) {
                if (copy_to_user(&buf[i], packet_length, packet_length_size))
                        goto out_unlock_msg_ctx;
                i += packet_length_size;
                if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))
                        goto out_unlock_msg_ctx;
                i += msg_ctx->msg_size;
        }
        rc = i;
        list_del(&msg_ctx->daemon_out_list);
        kfree(msg_ctx->msg);
        msg_ctx->msg = NULL;
        /* We do not expect a reply from the userspace daemon for any
         * message type other than ECRYPTFS_MSG_REQUEST */
        if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
                ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
out_unlock_msg_ctx:
        mutex_unlock(&msg_ctx->mux);
out_unlock_daemon:
        daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
        mutex_unlock(&daemon->mux);
        return rc;
}

/**
 * ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
 * @data: Bytes comprising struct ecryptfs_message
 * @data_size: sizeof(struct ecryptfs_message) + data len
 * @euid: Effective user id of miscdevess sending the miscdev response
 * @user_ns: The namespace in which @euid applies
 * @pid: Miscdevess id of miscdevess sending the miscdev response
 * @seq: Sequence number for miscdev response packet
 *
 * Returns zero on success; non-zero otherwise
 */
static int ecryptfs_miscdev_response(char *data, size_t data_size,
                                     uid_t euid, struct user_namespace *user_ns,
                                     struct pid *pid, u32 seq)
{
        struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
        int rc;

        if ((sizeof(*msg) + msg->data_len) != data_size) {
                printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
                       "[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
                       (sizeof(*msg) + msg->data_len), data_size);
                rc = -EINVAL;
                goto out;
        }
        rc = ecryptfs_process_response(msg, euid, user_ns, pid, seq);
        if (rc)
                printk(KERN_ERR
                       "Error processing response message; rc = [%d]\n", rc);
out:
        return rc;
}

/**
 * ecryptfs_miscdev_write - handle write to daemon miscdev handle
 * @file: File for misc dev handle (ignored)
 * @buf: Buffer containing user data
 * @count: Amount of data in @buf
 * @ppos: Pointer to offset in file (ignored)
 *
 * miscdevfs packet format:
 *  Octet 0: Type
 *  Octets 1-4: network byte order msg_ctx->counter (0's for non-response)
 *  Octets 5-N0: Size of struct ecryptfs_message to follow
 *  Octets N0-N1: struct ecryptfs_message (including data)
 *
 * 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)
{
        __be32 counter_nbo;
        u32 seq;
        size_t packet_size, packet_size_length, i;
        ssize_t sz = 0;
        char *data;
        uid_t euid = current_euid();
        unsigned char packet_size_peek[3];
        int rc;

        if (count == 0) {
                goto out;
        } else if (count == (1 + 4)) {
                /* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
                goto memdup;
        } else if (count < (1 + 4 + 1)
                   || count > (1 + 4 + 2 + sizeof(struct ecryptfs_message) + 4
                               + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)) {
                printk(KERN_WARNING "%s: Acceptable packet size range is "
                       "[%d-%lu], but amount of data written is [%zu].",
                       __func__, (1 + 4 + 1),
                       (1 + 4 + 2 + sizeof(struct ecryptfs_message) + 4
                        + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES), count);
                return -EINVAL;
        }

        if (copy_from_user(packet_size_peek, (buf + 1 + 4),
                           sizeof(packet_size_peek))) {
                printk(KERN_WARNING "%s: Error while inspecting packet size\n",
                       __func__);
                return -EFAULT;
        }

        rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
                                          &packet_size_length);
        if (rc) {
                printk(KERN_WARNING "%s: Error parsing packet length; "
                       "rc = [%d]\n", __func__, rc);
                return rc;
        }

        if ((1 + 4 + packet_size_length + packet_size) != count) {
                printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
                       packet_size);
                return -EINVAL;
        }

memdup:
        data = memdup_user(buf, count);
        if (IS_ERR(data)) {
                printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
                       __func__, PTR_ERR(data));
                goto out;
        }
        sz = count;
        i = 0;
        switch (data[i++]) {
        case ECRYPTFS_MSG_RESPONSE:
                if (count < (1 + 4 + 1 + sizeof(struct ecryptfs_message))) {
                        printk(KERN_WARNING "%s: Minimum acceptable packet "
                               "size is [%zd], but amount of data written is "
                               "only [%zd]. Discarding response packet.\n",
                               __func__,
                               (1 + 4 + 1 + sizeof(struct ecryptfs_message)),
                               count);
                        goto out_free;
                }
                memcpy(&counter_nbo, &data[i], 4);
                seq = be32_to_cpu(counter_nbo);
                i += 4 + packet_size_length;
                rc = ecryptfs_miscdev_response(&data[i], packet_size,
                                               euid, current_user_ns(),
                                               task_pid(current), seq);
                if (rc)
                        printk(KERN_WARNING "%s: Failed to deliver miscdev "
                               "response to requesting operation; rc = [%d]\n",
                               __func__, rc);
                break;
        case ECRYPTFS_MSG_HELO:
        case ECRYPTFS_MSG_QUIT:
                break;
        default:
                ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
                                "message of unrecognized type [%d]\n",
                                data[0]);
                break;
        }
out_free:
        kfree(data);
out:
        return sz;
}


static const struct file_operations ecryptfs_miscdev_fops = {
        .open    = ecryptfs_miscdev_open,
        .poll    = ecryptfs_miscdev_poll,
        .read    = ecryptfs_miscdev_read,
        .write   = ecryptfs_miscdev_write,
        .release = ecryptfs_miscdev_release,
};

static struct miscdevice ecryptfs_miscdev = {
        .minor = MISC_DYNAMIC_MINOR,
        .name  = "ecryptfs",
        .fops  = &ecryptfs_miscdev_fops
};

/**
 * 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 ecryptfs_init_ecryptfs_miscdev(void)
{
        int rc;

        atomic_set(&ecryptfs_num_miscdev_opens, 0);
        rc = misc_register(&ecryptfs_miscdev);
        if (rc)
                printk(KERN_ERR "%s: Failed to register miscellaneous device "
                       "for communications with userspace daemons; rc = [%d]\n",
                       __func__, rc);
        return rc;
}

/**
 * ecryptfs_destroy_ecryptfs_miscdev
 *
 * All of the daemons must be exorcised prior to calling this
 * function.
 */
void ecryptfs_destroy_ecryptfs_miscdev(void)
{
        BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
        misc_deregister(&ecryptfs_miscdev);
}