1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include <linux/types.h>
4 #include <linux/kconfig.h>
5 #include <linux/list.h>
6 #include <linux/slab.h>
7 #include <linux/security.h>
8 #include <linux/highmem.h>
9 #include <linux/umh.h>
10 #include <linux/sysctl.h>
11 #include <linux/vmalloc.h>
12 #include <linux/module.h>
13 
14 #include "fallback.h"
15 #include "firmware.h"
16 
17 /*
18  * firmware fallback mechanism
19  */
20 
21 MODULE_IMPORT_NS(FIRMWARE_LOADER_PRIVATE);
22 
23 extern struct firmware_fallback_config fw_fallback_config;
24 
25 /* These getters are vetted to use int properly */
26 static inline int __firmware_loading_timeout(void)
27 {
28 	return fw_fallback_config.loading_timeout;
29 }
30 
31 /* These setters are vetted to use int properly */
32 static void __fw_fallback_set_timeout(int timeout)
33 {
34 	fw_fallback_config.loading_timeout = timeout;
35 }
36 
37 /*
38  * use small loading timeout for caching devices' firmware because all these
39  * firmware images have been loaded successfully at lease once, also system is
40  * ready for completing firmware loading now. The maximum size of firmware in
41  * current distributions is about 2M bytes, so 10 secs should be enough.
42  */
43 void fw_fallback_set_cache_timeout(void)
44 {
45 	fw_fallback_config.old_timeout = __firmware_loading_timeout();
46 	__fw_fallback_set_timeout(10);
47 }
48 
49 /* Restores the timeout to the value last configured during normal operation */
50 void fw_fallback_set_default_timeout(void)
51 {
52 	__fw_fallback_set_timeout(fw_fallback_config.old_timeout);
53 }
54 
55 static long firmware_loading_timeout(void)
56 {
57 	return __firmware_loading_timeout() > 0 ?
58 		__firmware_loading_timeout() * HZ : MAX_JIFFY_OFFSET;
59 }
60 
61 static inline bool fw_sysfs_done(struct fw_priv *fw_priv)
62 {
63 	return __fw_state_check(fw_priv, FW_STATUS_DONE);
64 }
65 
66 static inline bool fw_sysfs_loading(struct fw_priv *fw_priv)
67 {
68 	return __fw_state_check(fw_priv, FW_STATUS_LOADING);
69 }
70 
71 static inline int fw_sysfs_wait_timeout(struct fw_priv *fw_priv,  long timeout)
72 {
73 	return __fw_state_wait_common(fw_priv, timeout);
74 }
75 
76 struct fw_sysfs {
77 	bool nowait;
78 	struct device dev;
79 	struct fw_priv *fw_priv;
80 	struct firmware *fw;
81 };
82 
83 static struct fw_sysfs *to_fw_sysfs(struct device *dev)
84 {
85 	return container_of(dev, struct fw_sysfs, dev);
86 }
87 
88 static void __fw_load_abort(struct fw_priv *fw_priv)
89 {
90 	/*
91 	 * There is a small window in which user can write to 'loading'
92 	 * between loading done and disappearance of 'loading'
93 	 */
94 	if (fw_sysfs_done(fw_priv))
95 		return;
96 
97 	list_del_init(&fw_priv->pending_list);
98 	fw_state_aborted(fw_priv);
99 }
100 
101 static void fw_load_abort(struct fw_sysfs *fw_sysfs)
102 {
103 	struct fw_priv *fw_priv = fw_sysfs->fw_priv;
104 
105 	__fw_load_abort(fw_priv);
106 }
107 
108 static LIST_HEAD(pending_fw_head);
109 
110 void kill_pending_fw_fallback_reqs(bool only_kill_custom)
111 {
112 	struct fw_priv *fw_priv;
113 	struct fw_priv *next;
114 
115 	mutex_lock(&fw_lock);
116 	list_for_each_entry_safe(fw_priv, next, &pending_fw_head,
117 				 pending_list) {
118 		if (!fw_priv->need_uevent || !only_kill_custom)
119 			 __fw_load_abort(fw_priv);
120 	}
121 	mutex_unlock(&fw_lock);
122 }
123 
124 static ssize_t timeout_show(struct class *class, struct class_attribute *attr,
125 			    char *buf)
126 {
127 	return sprintf(buf, "%d\n", __firmware_loading_timeout());
128 }
129 
130 /**
131  * firmware_timeout_store() - set number of seconds to wait for firmware
132  * @class: device class pointer
133  * @attr: device attribute pointer
134  * @buf: buffer to scan for timeout value
135  * @count: number of bytes in @buf
136  *
137  *	Sets the number of seconds to wait for the firmware.  Once
138  *	this expires an error will be returned to the driver and no
139  *	firmware will be provided.
140  *
141  *	Note: zero means 'wait forever'.
142  **/
143 static ssize_t timeout_store(struct class *class, struct class_attribute *attr,
144 			     const char *buf, size_t count)
145 {
146 	int tmp_loading_timeout = simple_strtol(buf, NULL, 10);
147 
148 	if (tmp_loading_timeout < 0)
149 		tmp_loading_timeout = 0;
150 
151 	__fw_fallback_set_timeout(tmp_loading_timeout);
152 
153 	return count;
154 }
155 static CLASS_ATTR_RW(timeout);
156 
157 static struct attribute *firmware_class_attrs[] = {
158 	&class_attr_timeout.attr,
159 	NULL,
160 };
161 ATTRIBUTE_GROUPS(firmware_class);
162 
163 static void fw_dev_release(struct device *dev)
164 {
165 	struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
166 
167 	kfree(fw_sysfs);
168 }
169 
170 static int do_firmware_uevent(struct fw_sysfs *fw_sysfs, struct kobj_uevent_env *env)
171 {
172 	if (add_uevent_var(env, "FIRMWARE=%s", fw_sysfs->fw_priv->fw_name))
173 		return -ENOMEM;
174 	if (add_uevent_var(env, "TIMEOUT=%i", __firmware_loading_timeout()))
175 		return -ENOMEM;
176 	if (add_uevent_var(env, "ASYNC=%d", fw_sysfs->nowait))
177 		return -ENOMEM;
178 
179 	return 0;
180 }
181 
182 static int firmware_uevent(struct device *dev, struct kobj_uevent_env *env)
183 {
184 	struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
185 	int err = 0;
186 
187 	mutex_lock(&fw_lock);
188 	if (fw_sysfs->fw_priv)
189 		err = do_firmware_uevent(fw_sysfs, env);
190 	mutex_unlock(&fw_lock);
191 	return err;
192 }
193 
194 static struct class firmware_class = {
195 	.name		= "firmware",
196 	.class_groups	= firmware_class_groups,
197 	.dev_uevent	= firmware_uevent,
198 	.dev_release	= fw_dev_release,
199 };
200 
201 int register_sysfs_loader(void)
202 {
203 	return class_register(&firmware_class);
204 }
205 
206 void unregister_sysfs_loader(void)
207 {
208 	class_unregister(&firmware_class);
209 }
210 
211 static ssize_t firmware_loading_show(struct device *dev,
212 				     struct device_attribute *attr, char *buf)
213 {
214 	struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
215 	int loading = 0;
216 
217 	mutex_lock(&fw_lock);
218 	if (fw_sysfs->fw_priv)
219 		loading = fw_sysfs_loading(fw_sysfs->fw_priv);
220 	mutex_unlock(&fw_lock);
221 
222 	return sprintf(buf, "%d\n", loading);
223 }
224 
225 /**
226  * firmware_loading_store() - set value in the 'loading' control file
227  * @dev: device pointer
228  * @attr: device attribute pointer
229  * @buf: buffer to scan for loading control value
230  * @count: number of bytes in @buf
231  *
232  *	The relevant values are:
233  *
234  *	 1: Start a load, discarding any previous partial load.
235  *	 0: Conclude the load and hand the data to the driver code.
236  *	-1: Conclude the load with an error and discard any written data.
237  **/
238 static ssize_t firmware_loading_store(struct device *dev,
239 				      struct device_attribute *attr,
240 				      const char *buf, size_t count)
241 {
242 	struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
243 	struct fw_priv *fw_priv;
244 	ssize_t written = count;
245 	int loading = simple_strtol(buf, NULL, 10);
246 
247 	mutex_lock(&fw_lock);
248 	fw_priv = fw_sysfs->fw_priv;
249 	if (fw_state_is_aborted(fw_priv))
250 		goto out;
251 
252 	switch (loading) {
253 	case 1:
254 		/* discarding any previous partial load */
255 		if (!fw_sysfs_done(fw_priv)) {
256 			fw_free_paged_buf(fw_priv);
257 			fw_state_start(fw_priv);
258 		}
259 		break;
260 	case 0:
261 		if (fw_sysfs_loading(fw_priv)) {
262 			int rc;
263 
264 			/*
265 			 * Several loading requests may be pending on
266 			 * one same firmware buf, so let all requests
267 			 * see the mapped 'buf->data' once the loading
268 			 * is completed.
269 			 * */
270 			rc = fw_map_paged_buf(fw_priv);
271 			if (rc)
272 				dev_err(dev, "%s: map pages failed\n",
273 					__func__);
274 			else
275 				rc = security_kernel_post_read_file(NULL,
276 						fw_priv->data, fw_priv->size,
277 						READING_FIRMWARE);
278 
279 			/*
280 			 * Same logic as fw_load_abort, only the DONE bit
281 			 * is ignored and we set ABORT only on failure.
282 			 */
283 			list_del_init(&fw_priv->pending_list);
284 			if (rc) {
285 				fw_state_aborted(fw_priv);
286 				written = rc;
287 			} else {
288 				fw_state_done(fw_priv);
289 			}
290 			break;
291 		}
292 		/* fallthrough */
293 	default:
294 		dev_err(dev, "%s: unexpected value (%d)\n", __func__, loading);
295 		/* fallthrough */
296 	case -1:
297 		fw_load_abort(fw_sysfs);
298 		break;
299 	}
300 out:
301 	mutex_unlock(&fw_lock);
302 	return written;
303 }
304 
305 static DEVICE_ATTR(loading, 0644, firmware_loading_show, firmware_loading_store);
306 
307 static void firmware_rw_data(struct fw_priv *fw_priv, char *buffer,
308 			   loff_t offset, size_t count, bool read)
309 {
310 	if (read)
311 		memcpy(buffer, fw_priv->data + offset, count);
312 	else
313 		memcpy(fw_priv->data + offset, buffer, count);
314 }
315 
316 static void firmware_rw(struct fw_priv *fw_priv, char *buffer,
317 			loff_t offset, size_t count, bool read)
318 {
319 	while (count) {
320 		void *page_data;
321 		int page_nr = offset >> PAGE_SHIFT;
322 		int page_ofs = offset & (PAGE_SIZE-1);
323 		int page_cnt = min_t(size_t, PAGE_SIZE - page_ofs, count);
324 
325 		page_data = kmap(fw_priv->pages[page_nr]);
326 
327 		if (read)
328 			memcpy(buffer, page_data + page_ofs, page_cnt);
329 		else
330 			memcpy(page_data + page_ofs, buffer, page_cnt);
331 
332 		kunmap(fw_priv->pages[page_nr]);
333 		buffer += page_cnt;
334 		offset += page_cnt;
335 		count -= page_cnt;
336 	}
337 }
338 
339 static ssize_t firmware_data_read(struct file *filp, struct kobject *kobj,
340 				  struct bin_attribute *bin_attr,
341 				  char *buffer, loff_t offset, size_t count)
342 {
343 	struct device *dev = kobj_to_dev(kobj);
344 	struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
345 	struct fw_priv *fw_priv;
346 	ssize_t ret_count;
347 
348 	mutex_lock(&fw_lock);
349 	fw_priv = fw_sysfs->fw_priv;
350 	if (!fw_priv || fw_sysfs_done(fw_priv)) {
351 		ret_count = -ENODEV;
352 		goto out;
353 	}
354 	if (offset > fw_priv->size) {
355 		ret_count = 0;
356 		goto out;
357 	}
358 	if (count > fw_priv->size - offset)
359 		count = fw_priv->size - offset;
360 
361 	ret_count = count;
362 
363 	if (fw_priv->data)
364 		firmware_rw_data(fw_priv, buffer, offset, count, true);
365 	else
366 		firmware_rw(fw_priv, buffer, offset, count, true);
367 
368 out:
369 	mutex_unlock(&fw_lock);
370 	return ret_count;
371 }
372 
373 static int fw_realloc_pages(struct fw_sysfs *fw_sysfs, int min_size)
374 {
375 	int err;
376 
377 	err = fw_grow_paged_buf(fw_sysfs->fw_priv,
378 				PAGE_ALIGN(min_size) >> PAGE_SHIFT);
379 	if (err)
380 		fw_load_abort(fw_sysfs);
381 	return err;
382 }
383 
384 /**
385  * firmware_data_write() - write method for firmware
386  * @filp: open sysfs file
387  * @kobj: kobject for the device
388  * @bin_attr: bin_attr structure
389  * @buffer: buffer being written
390  * @offset: buffer offset for write in total data store area
391  * @count: buffer size
392  *
393  *	Data written to the 'data' attribute will be later handed to
394  *	the driver as a firmware image.
395  **/
396 static ssize_t firmware_data_write(struct file *filp, struct kobject *kobj,
397 				   struct bin_attribute *bin_attr,
398 				   char *buffer, loff_t offset, size_t count)
399 {
400 	struct device *dev = kobj_to_dev(kobj);
401 	struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
402 	struct fw_priv *fw_priv;
403 	ssize_t retval;
404 
405 	if (!capable(CAP_SYS_RAWIO))
406 		return -EPERM;
407 
408 	mutex_lock(&fw_lock);
409 	fw_priv = fw_sysfs->fw_priv;
410 	if (!fw_priv || fw_sysfs_done(fw_priv)) {
411 		retval = -ENODEV;
412 		goto out;
413 	}
414 
415 	if (fw_priv->data) {
416 		if (offset + count > fw_priv->allocated_size) {
417 			retval = -ENOMEM;
418 			goto out;
419 		}
420 		firmware_rw_data(fw_priv, buffer, offset, count, false);
421 		retval = count;
422 	} else {
423 		retval = fw_realloc_pages(fw_sysfs, offset + count);
424 		if (retval)
425 			goto out;
426 
427 		retval = count;
428 		firmware_rw(fw_priv, buffer, offset, count, false);
429 	}
430 
431 	fw_priv->size = max_t(size_t, offset + count, fw_priv->size);
432 out:
433 	mutex_unlock(&fw_lock);
434 	return retval;
435 }
436 
437 static struct bin_attribute firmware_attr_data = {
438 	.attr = { .name = "data", .mode = 0644 },
439 	.size = 0,
440 	.read = firmware_data_read,
441 	.write = firmware_data_write,
442 };
443 
444 static struct attribute *fw_dev_attrs[] = {
445 	&dev_attr_loading.attr,
446 	NULL
447 };
448 
449 static struct bin_attribute *fw_dev_bin_attrs[] = {
450 	&firmware_attr_data,
451 	NULL
452 };
453 
454 static const struct attribute_group fw_dev_attr_group = {
455 	.attrs = fw_dev_attrs,
456 	.bin_attrs = fw_dev_bin_attrs,
457 };
458 
459 static const struct attribute_group *fw_dev_attr_groups[] = {
460 	&fw_dev_attr_group,
461 	NULL
462 };
463 
464 static struct fw_sysfs *
465 fw_create_instance(struct firmware *firmware, const char *fw_name,
466 		   struct device *device, u32 opt_flags)
467 {
468 	struct fw_sysfs *fw_sysfs;
469 	struct device *f_dev;
470 
471 	fw_sysfs = kzalloc(sizeof(*fw_sysfs), GFP_KERNEL);
472 	if (!fw_sysfs) {
473 		fw_sysfs = ERR_PTR(-ENOMEM);
474 		goto exit;
475 	}
476 
477 	fw_sysfs->nowait = !!(opt_flags & FW_OPT_NOWAIT);
478 	fw_sysfs->fw = firmware;
479 	f_dev = &fw_sysfs->dev;
480 
481 	device_initialize(f_dev);
482 	dev_set_name(f_dev, "%s", fw_name);
483 	f_dev->parent = device;
484 	f_dev->class = &firmware_class;
485 	f_dev->groups = fw_dev_attr_groups;
486 exit:
487 	return fw_sysfs;
488 }
489 
490 /**
491  * fw_load_sysfs_fallback() - load a firmware via the sysfs fallback mechanism
492  * @fw_sysfs: firmware sysfs information for the firmware to load
493  * @opt_flags: flags of options, FW_OPT_*
494  * @timeout: timeout to wait for the load
495  *
496  * In charge of constructing a sysfs fallback interface for firmware loading.
497  **/
498 static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs,
499 				  u32 opt_flags, long timeout)
500 {
501 	int retval = 0;
502 	struct device *f_dev = &fw_sysfs->dev;
503 	struct fw_priv *fw_priv = fw_sysfs->fw_priv;
504 
505 	/* fall back on userspace loading */
506 	if (!fw_priv->data)
507 		fw_priv->is_paged_buf = true;
508 
509 	dev_set_uevent_suppress(f_dev, true);
510 
511 	retval = device_add(f_dev);
512 	if (retval) {
513 		dev_err(f_dev, "%s: device_register failed\n", __func__);
514 		goto err_put_dev;
515 	}
516 
517 	mutex_lock(&fw_lock);
518 	list_add(&fw_priv->pending_list, &pending_fw_head);
519 	mutex_unlock(&fw_lock);
520 
521 	if (opt_flags & FW_OPT_UEVENT) {
522 		fw_priv->need_uevent = true;
523 		dev_set_uevent_suppress(f_dev, false);
524 		dev_dbg(f_dev, "firmware: requesting %s\n", fw_priv->fw_name);
525 		kobject_uevent(&fw_sysfs->dev.kobj, KOBJ_ADD);
526 	} else {
527 		timeout = MAX_JIFFY_OFFSET;
528 	}
529 
530 	retval = fw_sysfs_wait_timeout(fw_priv, timeout);
531 	if (retval < 0 && retval != -ENOENT) {
532 		mutex_lock(&fw_lock);
533 		fw_load_abort(fw_sysfs);
534 		mutex_unlock(&fw_lock);
535 	}
536 
537 	if (fw_state_is_aborted(fw_priv)) {
538 		if (retval == -ERESTARTSYS)
539 			retval = -EINTR;
540 		else
541 			retval = -EAGAIN;
542 	} else if (fw_priv->is_paged_buf && !fw_priv->data)
543 		retval = -ENOMEM;
544 
545 	device_del(f_dev);
546 err_put_dev:
547 	put_device(f_dev);
548 	return retval;
549 }
550 
551 static int fw_load_from_user_helper(struct firmware *firmware,
552 				    const char *name, struct device *device,
553 				    u32 opt_flags)
554 {
555 	struct fw_sysfs *fw_sysfs;
556 	long timeout;
557 	int ret;
558 
559 	timeout = firmware_loading_timeout();
560 	if (opt_flags & FW_OPT_NOWAIT) {
561 		timeout = usermodehelper_read_lock_wait(timeout);
562 		if (!timeout) {
563 			dev_dbg(device, "firmware: %s loading timed out\n",
564 				name);
565 			return -EBUSY;
566 		}
567 	} else {
568 		ret = usermodehelper_read_trylock();
569 		if (WARN_ON(ret)) {
570 			dev_err(device, "firmware: %s will not be loaded\n",
571 				name);
572 			return ret;
573 		}
574 	}
575 
576 	fw_sysfs = fw_create_instance(firmware, name, device, opt_flags);
577 	if (IS_ERR(fw_sysfs)) {
578 		ret = PTR_ERR(fw_sysfs);
579 		goto out_unlock;
580 	}
581 
582 	fw_sysfs->fw_priv = firmware->priv;
583 	ret = fw_load_sysfs_fallback(fw_sysfs, opt_flags, timeout);
584 
585 	if (!ret)
586 		ret = assign_fw(firmware, device, opt_flags);
587 
588 out_unlock:
589 	usermodehelper_read_unlock();
590 
591 	return ret;
592 }
593 
594 static bool fw_force_sysfs_fallback(u32 opt_flags)
595 {
596 	if (fw_fallback_config.force_sysfs_fallback)
597 		return true;
598 	if (!(opt_flags & FW_OPT_USERHELPER))
599 		return false;
600 	return true;
601 }
602 
603 static bool fw_run_sysfs_fallback(u32 opt_flags)
604 {
605 	int ret;
606 
607 	if (fw_fallback_config.ignore_sysfs_fallback) {
608 		pr_info_once("Ignoring firmware sysfs fallback due to sysctl knob\n");
609 		return false;
610 	}
611 
612 	if ((opt_flags & FW_OPT_NOFALLBACK_SYSFS))
613 		return false;
614 
615 	/* Also permit LSMs and IMA to fail firmware sysfs fallback */
616 	ret = security_kernel_load_data(LOADING_FIRMWARE);
617 	if (ret < 0)
618 		return false;
619 
620 	return fw_force_sysfs_fallback(opt_flags);
621 }
622 
623 /**
624  * firmware_fallback_sysfs() - use the fallback mechanism to find firmware
625  * @fw: pointer to firmware image
626  * @name: name of firmware file to look for
627  * @device: device for which firmware is being loaded
628  * @opt_flags: options to control firmware loading behaviour
629  * @ret: return value from direct lookup which triggered the fallback mechanism
630  *
631  * This function is called if direct lookup for the firmware failed, it enables
632  * a fallback mechanism through userspace by exposing a sysfs loading
633  * interface. Userspace is in charge of loading the firmware through the sysfs
634  * loading interface. This sysfs fallback mechanism may be disabled completely
635  * on a system by setting the proc sysctl value ignore_sysfs_fallback to true.
636  * If this is false we check if the internal API caller set the
637  * @FW_OPT_NOFALLBACK_SYSFS flag, if so it would also disable the fallback
638  * mechanism. A system may want to enforce the sysfs fallback mechanism at all
639  * times, it can do this by setting ignore_sysfs_fallback to false and
640  * force_sysfs_fallback to true.
641  * Enabling force_sysfs_fallback is functionally equivalent to build a kernel
642  * with CONFIG_FW_LOADER_USER_HELPER_FALLBACK.
643  **/
644 int firmware_fallback_sysfs(struct firmware *fw, const char *name,
645 			    struct device *device,
646 			    u32 opt_flags,
647 			    int ret)
648 {
649 	if (!fw_run_sysfs_fallback(opt_flags))
650 		return ret;
651 
652 	if (!(opt_flags & FW_OPT_NO_WARN))
653 		dev_warn(device, "Falling back to sysfs fallback for: %s\n",
654 				 name);
655 	else
656 		dev_dbg(device, "Falling back to sysfs fallback for: %s\n",
657 				name);
658 	return fw_load_from_user_helper(fw, name, device, opt_flags);
659 }
660