drivers/char/tpm/tpm-dev-common.c

   1 /*
   2  * Copyright (C) 2004 IBM Corporation
   3  * Authors:
   4  * Leendert van Doorn <leendert@watson.ibm.com>
   5  * Dave Safford <safford@watson.ibm.com>
   6  * Reiner Sailer <sailer@watson.ibm.com>
   7  * Kylene Hall <kjhall@us.ibm.com>
   8  *
   9  * Copyright (C) 2013 Obsidian Research Corp
  10  * Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
  11  *
  12  * Device file system interface to the TPM
  13  *
  14  * This program is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU General Public License as
  16  * published by the Free Software Foundation, version 2 of the
  17  * License.
  18  *
  19  */
  20 #include <linux/slab.h>
  21 #include <linux/uaccess.h>
  22 #include "tpm.h"
  23 #include "tpm-dev.h"
  24
  25 static void user_reader_timeout(struct timer_list *t)
  26 {
  27         struct file_priv *priv = from_timer(priv, t, user_read_timer);
  28
  29         pr_warn("TPM user space timeout is deprecated (pid=%d)\n",
  30                 task_tgid_nr(current));
  31
  32         schedule_work(&priv->work);
  33 }
  34
  35 static void timeout_work(struct work_struct *work)
  36 {
  37         struct file_priv *priv = container_of(work, struct file_priv, work);
  38
  39         mutex_lock(&priv->buffer_mutex);
  40         atomic_set(&priv->data_pending, 0);
  41         memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
  42         mutex_unlock(&priv->buffer_mutex);
  43 }
  44
  45 void tpm_common_open(struct file *file, struct tpm_chip *chip,
  46                      struct file_priv *priv)
  47 {
  48         priv->chip = chip;
  49         atomic_set(&priv->data_pending, 0);
  50         mutex_init(&priv->buffer_mutex);
  51         timer_setup(&priv->user_read_timer, user_reader_timeout, 0);
  52         INIT_WORK(&priv->work, timeout_work);
  53
  54         file->private_data = priv;
  55 }
  56
  57 ssize_t tpm_common_read(struct file *file, char __user *buf,
  58                         size_t size, loff_t *off)
  59 {
  60         struct file_priv *priv = file->private_data;
  61         ssize_t ret_size;
  62         ssize_t orig_ret_size;
  63         int rc;
  64
  65         del_singleshot_timer_sync(&priv->user_read_timer);
  66         flush_work(&priv->work);
  67         ret_size = atomic_read(&priv->data_pending);
  68         if (ret_size > 0) {     /* relay data */
  69                 orig_ret_size = ret_size;
  70                 if (size < ret_size)
  71                         ret_size = size;
  72
  73                 mutex_lock(&priv->buffer_mutex);
  74                 rc = copy_to_user(buf, priv->data_buffer, ret_size);
  75                 memset(priv->data_buffer, 0, orig_ret_size);
  76                 if (rc)
  77                         ret_size = -EFAULT;
  78
  79                 mutex_unlock(&priv->buffer_mutex);
  80         }
  81
  82         atomic_set(&priv->data_pending, 0);
  83
  84         return ret_size;
  85 }
  86
  87 ssize_t tpm_common_write(struct file *file, const char __user *buf,
  88                          size_t size, loff_t *off, struct tpm_space *space)
  89 {
  90         struct file_priv *priv = file->private_data;
  91         size_t in_size = size;
  92         ssize_t out_size;
  93
  94         /* Cannot perform a write until the read has cleared either via
  95          * tpm_read or a user_read_timer timeout. This also prevents split
  96          * buffered writes from blocking here.
  97          */
  98         if (atomic_read(&priv->data_pending) != 0)
  99                 return -EBUSY;
 100
 101         if (in_size > TPM_BUFSIZE)
 102                 return -E2BIG;
 103
 104         mutex_lock(&priv->buffer_mutex);
 105
 106         if (copy_from_user
 107             (priv->data_buffer, (void __user *) buf, in_size)) {
 108                 mutex_unlock(&priv->buffer_mutex);
 109                 return -EFAULT;
 110         }
 111
 112         if (in_size < 6 ||
 113             in_size < be32_to_cpu(*((__be32 *) (priv->data_buffer + 2)))) {
 114                 mutex_unlock(&priv->buffer_mutex);
 115                 return -EINVAL;
 116         }
 117
 118         /* atomic tpm command send and result receive. We only hold the ops
 119          * lock during this period so that the tpm can be unregistered even if
 120          * the char dev is held open.
 121          */
 122         if (tpm_try_get_ops(priv->chip)) {
 123                 mutex_unlock(&priv->buffer_mutex);
 124                 return -EPIPE;
 125         }
 126         out_size = tpm_transmit(priv->chip, space, priv->data_buffer,
 127                                 sizeof(priv->data_buffer), 0);
 128
 129         tpm_put_ops(priv->chip);
 130         if (out_size < 0) {
 131                 mutex_unlock(&priv->buffer_mutex);
 132                 return out_size;
 133         }
 134
 135         atomic_set(&priv->data_pending, out_size);
 136         mutex_unlock(&priv->buffer_mutex);
 137
 138         /* Set a timeout by which the reader must come claim the result */
 139         mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
 140
 141         return in_size;
 142 }
 143
 144 /*
 145  * Called on file close
 146  */
 147 void tpm_common_release(struct file *file, struct file_priv *priv)
 148 {
 149         del_singleshot_timer_sync(&priv->user_read_timer);
 150         flush_work(&priv->work);
 151         file->private_data = NULL;
 152         atomic_set(&priv->data_pending, 0);
 153 }