miscdev.c

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#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;

static unsigned int
ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
{
    struct ecryptfs_daemon *daemon = file->private_data;
    unsigned int mask = 0;

    mutex_lock(&daemon->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;
}

static int
ecryptfs_miscdev_open(struct inode *inode, struct file *file)
{
    struct ecryptfs_daemon *daemon = NULL;
    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);
    if (!rc) {
        rc = -EINVAL;
        goto out_unlock_daemon_list;
    }
    rc = ecryptfs_spawn_daemon(&daemon, file);
    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->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
        rc = -EBUSY;
        goto out_unlock_daemon;
    }
    daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
    file->private_data = daemon;
    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;
}

static int
ecryptfs_miscdev_release(struct inode *inode, struct file *file)
{
    struct ecryptfs_daemon *daemon = file->private_data;
    int rc;

    mutex_lock(&daemon->mux);
    BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
    daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
    atomic_dec(&ecryptfs_num_miscdev_opens);
    mutex_unlock(&daemon->mux);

    mutex_lock(&ecryptfs_daemon_hash_mux);
    rc = ecryptfs_exorcise_daemon(daemon);
    mutex_unlock(&ecryptfs_daemon_hash_mux);
    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);
    return rc;
}

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)
{
    struct ecryptfs_message *msg;

    msg = kmalloc((sizeof(*msg) + data_size), GFP_KERNEL);
    if (!msg) {
        printk(KERN_ERR "%s: Out of memory whilst attempting "
               "to kmalloc(%zd, GFP_KERNEL)\n", __func__,
               (sizeof(*msg) + data_size));
        return -ENOMEM;
    }

    mutex_lock(&msg_ctx->mux);
    msg_ctx->msg = msg;
    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);
    list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
    mutex_unlock(&msg_ctx->mux);

    mutex_lock(&daemon->mux);
    daemon->num_queued_msg_ctx++;
    wake_up_interruptible(&daemon->wait);
    mutex_unlock(&daemon->mux);

    return 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
 */
#define PKT_TYPE_SIZE       1
#define PKT_CTR_SIZE        4
#define MIN_NON_MSG_PKT_SIZE    (PKT_TYPE_SIZE + PKT_CTR_SIZE)
#define MIN_MSG_PKT_SIZE    (PKT_TYPE_SIZE + PKT_CTR_SIZE \
                 + ECRYPTFS_MIN_PKT_LEN_SIZE)
/* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
#define MAX_MSG_PKT_SIZE    (PKT_TYPE_SIZE + PKT_CTR_SIZE \
                 + ECRYPTFS_MAX_PKT_LEN_SIZE \
                 + sizeof(struct ecryptfs_message) \
                 + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
#define PKT_TYPE_OFFSET     0
#define PKT_CTR_OFFSET      PKT_TYPE_SIZE
#define PKT_LEN_OFFSET      (PKT_TYPE_SIZE + PKT_CTR_SIZE)

static ssize_t
ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
              loff_t *ppos)
{
    struct ecryptfs_daemon *daemon = file->private_data;
    struct ecryptfs_msg_ctx *msg_ctx;
    size_t packet_length_size;
    char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
    size_t i;
    size_t total_length;
    int rc;

    mutex_lock(&daemon->mux);
    if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
        rc = 0;
        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;
        goto out_unlock_daemon;
    }
    /* This daemon will not go away so long as this flag is set */
    daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
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;
    }
    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;
    }
    total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + 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[PKT_CTR_OFFSET])))
        goto out_unlock_msg_ctx;
    i = PKT_TYPE_SIZE + PKT_CTR_SIZE;
    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;
}

static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
                     size_t data_size, 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(daemon, msg, seq);
    if (rc)
        printk(KERN_ERR
               "Error processing response message; rc = [%d]\n", rc);
out:
    return rc;
}

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;
    char *data;
    unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
    ssize_t rc;

    if (count == 0) {
        return 0;
    } else if (count == MIN_NON_MSG_PKT_SIZE) {
        /* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
        goto memdup;
    } else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) {
        printk(KERN_WARNING "%s: Acceptable packet size range is "
               "[%d-%zu], but amount of data written is [%zu].",
               __func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count);
        return -EINVAL;
    }

    if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET],
               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 = [%zd]\n", __func__, rc);
        return rc;
    }

    if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + 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));
        return PTR_ERR(data);
    }
    switch (data[PKT_TYPE_OFFSET]) {
    case ECRYPTFS_MSG_RESPONSE:
        if (count < (MIN_MSG_PKT_SIZE
                 + 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__,
                   (MIN_MSG_PKT_SIZE
                + sizeof(struct ecryptfs_message)), count);
            rc = -EINVAL;
            goto out_free;
        }
        memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
        seq = be32_to_cpu(counter_nbo);
        rc = ecryptfs_miscdev_response(file->private_data,
                &data[PKT_LEN_OFFSET + packet_size_length],
                packet_size, seq);
        if (rc) {
            printk(KERN_WARNING "%s: Failed to deliver miscdev "
                   "response to requesting operation; rc = [%zd]\n",
                   __func__, rc);
            goto out_free;
        }
        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]);
        rc = -EINVAL;
        goto out_free;
    }
    rc = count;
out_free:
    kfree(data);
    return rc;
}


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,
    .llseek  = noop_llseek,
};

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

int __init 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;
}

void ecryptfs_destroy_ecryptfs_miscdev(void)
{
    BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
    misc_deregister(&ecryptfs_miscdev);
}