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 
24 static 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 
51 out_rc:
52 	return ret ? ret : len;
53 }
54 
55 static 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 	}
82 out:
83 	mutex_unlock(&priv->buffer_mutex);
84 	wake_up_interruptible(&priv->async_wait);
85 }
86 
87 static 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 
97 static 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 
110 void 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 
125 ssize_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 
155 out:
156 	if (!priv->response_length) {
157 		*off = 0;
158 		del_singleshot_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 
165 ssize_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 	}
232 out:
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  */
262 void tpm_common_release(struct file *file, struct file_priv *priv)
263 {
264 	flush_work(&priv->async_work);
265 	del_singleshot_timer_sync(&priv->user_read_timer);
266 	flush_work(&priv->timeout_work);
267 	file->private_data = NULL;
268 	priv->response_length = 0;
269 }
270 
271 int __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 
278 void __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 }
285