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

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2004 IBM Corporation
   4  * Authors:
   5  * Leendert van Doorn <leendert@watson.ibm.com>
   6  * Dave Safford <safford@watson.ibm.com>
   7  * Reiner Sailer <sailer@watson.ibm.com>
   8  * Kylene Hall <kjhall@us.ibm.com>
   9  *
  10  * Copyright (C) 2013 Obsidian Research Corp
  11  * Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
  12  *
  13  * Device file system interface to the TPM
  14  */
  15 #include <linux/poll.h>
  16 #include <linux/slab.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/workqueue.h>
  19 #include "tpm.h"
  20 #include "tpm-dev.h"
  21
  22 static struct workqueue_struct *tpm_dev_wq;
  23 static DEFINE_MUTEX(tpm_dev_wq_lock);
  24
  25 static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
  26                                 u8 *buf, size_t bufsiz)
  27 {
  28         struct tpm_header *header = (void *)buf;
  29         ssize_t ret, len;
  30
  31         ret = tpm2_prepare_space(chip, space, buf, bufsiz);
  32         /* If the command is not implemented by the TPM, synthesize a
  33          * response with a TPM2_RC_COMMAND_CODE return for user-space.
  34          */
  35         if (ret == -EOPNOTSUPP) {
  36                 header->length = cpu_to_be32(sizeof(*header));
  37                 header->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
  38                 header->return_code = cpu_to_be32(TPM2_RC_COMMAND_CODE |
  39                                                   TSS2_RESMGR_TPM_RC_LAYER);
  40                 ret = sizeof(*header);
  41         }
  42         if (ret)
  43                 goto out_rc;
  44
  45         len = tpm_transmit(chip, buf, bufsiz);
  46         if (len < 0)
  47                 ret = len;
  48
  49         if (!ret)
  50                 ret = tpm2_commit_space(chip, space, buf, &len);
  51
  52 out_rc:
  53         return ret ? ret : len;
  54 }
  55
  56 static void tpm_dev_async_work(struct work_struct *work)
  57 {
  58         struct file_priv *priv =
  59                         container_of(work, struct file_priv, async_work);
  60         ssize_t ret;
  61
  62         mutex_lock(&priv->buffer_mutex);
  63         priv->command_enqueued = false;
  64         ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
  65                                sizeof(priv->data_buffer));
  66         tpm_put_ops(priv->chip);
  67         if (ret > 0) {
  68                 priv->response_length = ret;
  69                 mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
  70         }
  71         mutex_unlock(&priv->buffer_mutex);
  72         wake_up_interruptible(&priv->async_wait);
  73 }
  74
  75 static void user_reader_timeout(struct timer_list *t)
  76 {
  77         struct file_priv *priv = from_timer(priv, t, user_read_timer);
  78
  79         pr_warn("TPM user space timeout is deprecated (pid=%d)\n",
  80                 task_tgid_nr(current));
  81
  82         schedule_work(&priv->timeout_work);
  83 }
  84
  85 static void tpm_timeout_work(struct work_struct *work)
  86 {
  87         struct file_priv *priv = container_of(work, struct file_priv,
  88                                               timeout_work);
  89
  90         mutex_lock(&priv->buffer_mutex);
  91         priv->response_read = true;
  92         priv->response_length = 0;
  93         memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
  94         mutex_unlock(&priv->buffer_mutex);
  95         wake_up_interruptible(&priv->async_wait);
  96 }
  97
  98 void tpm_common_open(struct file *file, struct tpm_chip *chip,
  99                      struct file_priv *priv, struct tpm_space *space)
 100 {
 101         priv->chip = chip;
 102         priv->space = space;
 103         priv->response_read = true;
 104
 105         mutex_init(&priv->buffer_mutex);
 106         timer_setup(&priv->user_read_timer, user_reader_timeout, 0);
 107         INIT_WORK(&priv->timeout_work, tpm_timeout_work);
 108         INIT_WORK(&priv->async_work, tpm_dev_async_work);
 109         init_waitqueue_head(&priv->async_wait);
 110         file->private_data = priv;
 111 }
 112
 113 ssize_t tpm_common_read(struct file *file, char __user *buf,
 114                         size_t size, loff_t *off)
 115 {
 116         struct file_priv *priv = file->private_data;
 117         ssize_t ret_size = 0;
 118         int rc;
 119
 120         mutex_lock(&priv->buffer_mutex);
 121
 122         if (priv->response_length) {
 123                 priv->response_read = true;
 124
 125                 ret_size = min_t(ssize_t, size, priv->response_length);
 126                 if (!ret_size) {
 127                         priv->response_length = 0;
 128                         goto out;
 129                 }
 130
 131                 rc = copy_to_user(buf, priv->data_buffer + *off, ret_size);
 132                 if (rc) {
 133                         memset(priv->data_buffer, 0, TPM_BUFSIZE);
 134                         priv->response_length = 0;
 135                         ret_size = -EFAULT;
 136                 } else {
 137                         memset(priv->data_buffer + *off, 0, ret_size);
 138                         priv->response_length -= ret_size;
 139                         *off += ret_size;
 140                 }
 141         }
 142
 143 out:
 144         if (!priv->response_length) {
 145                 *off = 0;
 146                 del_singleshot_timer_sync(&priv->user_read_timer);
 147                 flush_work(&priv->timeout_work);
 148         }
 149         mutex_unlock(&priv->buffer_mutex);
 150         return ret_size;
 151 }
 152
 153 ssize_t tpm_common_write(struct file *file, const char __user *buf,
 154                          size_t size, loff_t *off)
 155 {
 156         struct file_priv *priv = file->private_data;
 157         int ret = 0;
 158
 159         if (size > TPM_BUFSIZE)
 160                 return -E2BIG;
 161
 162         mutex_lock(&priv->buffer_mutex);
 163
 164         /* Cannot perform a write until the read has cleared either via
 165          * tpm_read or a user_read_timer timeout. This also prevents split
 166          * buffered writes from blocking here.
 167          */
 168         if ((!priv->response_read && priv->response_length) ||
 169             priv->command_enqueued) {
 170                 ret = -EBUSY;
 171                 goto out;
 172         }
 173
 174         if (copy_from_user(priv->data_buffer, buf, size)) {
 175                 ret = -EFAULT;
 176                 goto out;
 177         }
 178
 179         if (size < 6 ||
 180             size < be32_to_cpu(*((__be32 *)(priv->data_buffer + 2)))) {
 181                 ret = -EINVAL;
 182                 goto out;
 183         }
 184
 185         /* atomic tpm command send and result receive. We only hold the ops
 186          * lock during this period so that the tpm can be unregistered even if
 187          * the char dev is held open.
 188          */
 189         if (tpm_try_get_ops(priv->chip)) {
 190                 ret = -EPIPE;
 191                 goto out;
 192         }
 193
 194         priv->response_length = 0;
 195         priv->response_read = false;
 196         *off = 0;
 197
 198         /*
 199          * If in nonblocking mode schedule an async job to send
 200          * the command return the size.
 201          * In case of error the err code will be returned in
 202          * the subsequent read call.
 203          */
 204         if (file->f_flags & O_NONBLOCK) {
 205                 priv->command_enqueued = true;
 206                 queue_work(tpm_dev_wq, &priv->async_work);
 207                 mutex_unlock(&priv->buffer_mutex);
 208                 return size;
 209         }
 210
 211         ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
 212                                sizeof(priv->data_buffer));
 213         tpm_put_ops(priv->chip);
 214
 215         if (ret > 0) {
 216                 priv->response_length = ret;
 217                 mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
 218                 ret = size;
 219         }
 220 out:
 221         mutex_unlock(&priv->buffer_mutex);
 222         return ret;
 223 }
 224
 225 __poll_t tpm_common_poll(struct file *file, poll_table *wait)
 226 {
 227         struct file_priv *priv = file->private_data;
 228         __poll_t mask = 0;
 229
 230         poll_wait(file, &priv->async_wait, wait);
 231         mutex_lock(&priv->buffer_mutex);
 232
 233         /*
 234          * The response_length indicates if there is still response
 235          * (or part of it) to be consumed. Partial reads decrease it
 236          * by the number of bytes read, and write resets it the zero.
 237          */
 238         if (priv->response_length)
 239                 mask = EPOLLIN | EPOLLRDNORM;
 240         else
 241                 mask = EPOLLOUT | EPOLLWRNORM;
 242
 243         mutex_unlock(&priv->buffer_mutex);
 244         return mask;
 245 }
 246
 247 /*
 248  * Called on file close
 249  */
 250 void tpm_common_release(struct file *file, struct file_priv *priv)
 251 {
 252         flush_work(&priv->async_work);
 253         del_singleshot_timer_sync(&priv->user_read_timer);
 254         flush_work(&priv->timeout_work);
 255         file->private_data = NULL;
 256         priv->response_length = 0;
 257 }
 258
 259 int __init tpm_dev_common_init(void)
 260 {
 261         tpm_dev_wq = alloc_workqueue("tpm_dev_wq", WQ_MEM_RECLAIM, 0);
 262
 263         return !tpm_dev_wq ? -ENOMEM : 0;
 264 }
 265
 266 void __exit tpm_dev_common_exit(void)
 267 {
 268         if (tpm_dev_wq) {
 269                 destroy_workqueue(tpm_dev_wq);
 270                 tpm_dev_wq = NULL;
 271         }
 272 }