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
 22static struct workqueue_struct *tpm_dev_wq;
 23
 24static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
 25				u8 *buf, size_t bufsiz)
 26{
 27	struct tpm_header *header = (void *)buf;
 28	ssize_t ret, len;
 29
 30	ret = tpm2_prepare_space(chip, space, buf, bufsiz);
 31	/* If the command is not implemented by the TPM, synthesize a
 32	 * response with a TPM2_RC_COMMAND_CODE return for user-space.
 33	 */
 34	if (ret == -EOPNOTSUPP) {
 35		header->length = cpu_to_be32(sizeof(*header));
 36		header->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
 37		header->return_code = cpu_to_be32(TPM2_RC_COMMAND_CODE |
 38						  TSS2_RESMGR_TPM_RC_LAYER);
 39		ret = sizeof(*header);
 40	}
 41	if (ret)
 42		goto out_rc;
 43
 44	len = tpm_transmit(chip, buf, bufsiz);
 45	if (len < 0)
 46		ret = len;
 47
 48	if (!ret)
 49		ret = tpm2_commit_space(chip, space, buf, &len);
 50
 51out_rc:
 52	return ret ? ret : len;
 53}
 54
 55static void tpm_dev_async_work(struct work_struct *work)
 56{
 57	struct file_priv *priv =
 58			container_of(work, struct file_priv, async_work);
 59	ssize_t ret;
 60
 61	mutex_lock(&priv->buffer_mutex);
 62	priv->command_enqueued = false;
 63	ret = tpm_try_get_ops(priv->chip);
 64	if (ret) {
 65		priv->response_length = ret;
 66		goto out;
 67	}
 68
 69	ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
 70			       sizeof(priv->data_buffer));
 71	tpm_put_ops(priv->chip);
 72
 73	/*
 74	 * If ret is > 0 then tpm_dev_transmit returned the size of the
 75	 * response. If ret is < 0 then tpm_dev_transmit failed and
 76	 * returned an error code.
 77	 */
 78	if (ret != 0) {
 79		priv->response_length = ret;
 80		mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
 81	}
 82out:
 83	mutex_unlock(&priv->buffer_mutex);
 84	wake_up_interruptible(&priv->async_wait);
 85}
 86
 87static void user_reader_timeout(struct timer_list *t)
 88{
 89	struct file_priv *priv = from_timer(priv, t, user_read_timer);
 90
 91	pr_warn("TPM user space timeout is deprecated (pid=%d)\n",
 92		task_tgid_nr(current));
 93
 94	schedule_work(&priv->timeout_work);
 95}
 96
 97static void tpm_timeout_work(struct work_struct *work)
 98{
 99	struct file_priv *priv = container_of(work, struct file_priv,
100					      timeout_work);
101
102	mutex_lock(&priv->buffer_mutex);
103	priv->response_read = true;
104	priv->response_length = 0;
105	memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
106	mutex_unlock(&priv->buffer_mutex);
107	wake_up_interruptible(&priv->async_wait);
108}
109
110void tpm_common_open(struct file *file, struct tpm_chip *chip,
111		     struct file_priv *priv, struct tpm_space *space)
112{
113	priv->chip = chip;
114	priv->space = space;
115	priv->response_read = true;
116
117	mutex_init(&priv->buffer_mutex);
118	timer_setup(&priv->user_read_timer, user_reader_timeout, 0);
119	INIT_WORK(&priv->timeout_work, tpm_timeout_work);
120	INIT_WORK(&priv->async_work, tpm_dev_async_work);
121	init_waitqueue_head(&priv->async_wait);
122	file->private_data = priv;
123}
124
125ssize_t tpm_common_read(struct file *file, char __user *buf,
126			size_t size, loff_t *off)
127{
128	struct file_priv *priv = file->private_data;
129	ssize_t ret_size = 0;
130	int rc;
131
132	mutex_lock(&priv->buffer_mutex);
133
134	if (priv->response_length) {
135		priv->response_read = true;
136
137		ret_size = min_t(ssize_t, size, priv->response_length);
138		if (ret_size <= 0) {
139			priv->response_length = 0;
140			goto out;
141		}
142
143		rc = copy_to_user(buf, priv->data_buffer + *off, ret_size);
144		if (rc) {
145			memset(priv->data_buffer, 0, TPM_BUFSIZE);
146			priv->response_length = 0;
147			ret_size = -EFAULT;
148		} else {
149			memset(priv->data_buffer + *off, 0, ret_size);
150			priv->response_length -= ret_size;
151			*off += ret_size;
152		}
153	}
154
155out:
156	if (!priv->response_length) {
157		*off = 0;
158		del_timer_sync(&priv->user_read_timer);
159		flush_work(&priv->timeout_work);
160	}
161	mutex_unlock(&priv->buffer_mutex);
162	return ret_size;
163}
164
165ssize_t tpm_common_write(struct file *file, const char __user *buf,
166			 size_t size, loff_t *off)
167{
168	struct file_priv *priv = file->private_data;
169	int ret = 0;
170
171	if (size > TPM_BUFSIZE)
172		return -E2BIG;
173
174	mutex_lock(&priv->buffer_mutex);
175
176	/* Cannot perform a write until the read has cleared either via
177	 * tpm_read or a user_read_timer timeout. This also prevents split
178	 * buffered writes from blocking here.
179	 */
180	if ((!priv->response_read && priv->response_length) ||
181	    priv->command_enqueued) {
182		ret = -EBUSY;
183		goto out;
184	}
185
186	if (copy_from_user(priv->data_buffer, buf, size)) {
187		ret = -EFAULT;
188		goto out;
189	}
190
191	if (size < 6 ||
192	    size < be32_to_cpu(*((__be32 *)(priv->data_buffer + 2)))) {
193		ret = -EINVAL;
194		goto out;
195	}
196
197	priv->response_length = 0;
198	priv->response_read = false;
199	*off = 0;
200
201	/*
202	 * If in nonblocking mode schedule an async job to send
203	 * the command return the size.
204	 * In case of error the err code will be returned in
205	 * the subsequent read call.
206	 */
207	if (file->f_flags & O_NONBLOCK) {
208		priv->command_enqueued = true;
209		queue_work(tpm_dev_wq, &priv->async_work);
210		mutex_unlock(&priv->buffer_mutex);
211		return size;
212	}
213
214	/* atomic tpm command send and result receive. We only hold the ops
215	 * lock during this period so that the tpm can be unregistered even if
216	 * the char dev is held open.
217	 */
218	if (tpm_try_get_ops(priv->chip)) {
219		ret = -EPIPE;
220		goto out;
221	}
222
223	ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
224			       sizeof(priv->data_buffer));
225	tpm_put_ops(priv->chip);
226
227	if (ret > 0) {
228		priv->response_length = ret;
229		mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
230		ret = size;
231	}
232out:
233	mutex_unlock(&priv->buffer_mutex);
234	return ret;
235}
236
237__poll_t tpm_common_poll(struct file *file, poll_table *wait)
238{
239	struct file_priv *priv = file->private_data;
240	__poll_t mask = 0;
241
242	poll_wait(file, &priv->async_wait, wait);
243	mutex_lock(&priv->buffer_mutex);
244
245	/*
246	 * The response_length indicates if there is still response
247	 * (or part of it) to be consumed. Partial reads decrease it
248	 * by the number of bytes read, and write resets it the zero.
249	 */
250	if (priv->response_length)
251		mask = EPOLLIN | EPOLLRDNORM;
252	else
253		mask = EPOLLOUT | EPOLLWRNORM;
254
255	mutex_unlock(&priv->buffer_mutex);
256	return mask;
257}
258
259/*
260 * Called on file close
261 */
262void tpm_common_release(struct file *file, struct file_priv *priv)
263{
264	flush_work(&priv->async_work);
265	del_timer_sync(&priv->user_read_timer);
266	flush_work(&priv->timeout_work);
267	file->private_data = NULL;
268	priv->response_length = 0;
269}
270
271int __init tpm_dev_common_init(void)
272{
273	tpm_dev_wq = alloc_workqueue("tpm_dev_wq", WQ_MEM_RECLAIM, 0);
274
275	return !tpm_dev_wq ? -ENOMEM : 0;
276}
277
278void __exit tpm_dev_common_exit(void)
279{
280	if (tpm_dev_wq) {
281		destroy_workqueue(tpm_dev_wq);
282		tpm_dev_wq = NULL;
283	}
284}