Loading...
Note: File does not exist in v3.15.
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright(c) 2014 Intel Mobile Communications GmbH
4 * Copyright(c) 2015 Intel Deutschland GmbH
5 *
6 * Author: Johannes Berg <johannes@sipsolutions.net>
7 */
8#include <linux/module.h>
9#include <linux/device.h>
10#include <linux/devcoredump.h>
11#include <linux/list.h>
12#include <linux/slab.h>
13#include <linux/fs.h>
14#include <linux/workqueue.h>
15
16static struct class devcd_class;
17
18/* global disable flag, for security purposes */
19static bool devcd_disabled;
20
21struct devcd_entry {
22 struct device devcd_dev;
23 void *data;
24 size_t datalen;
25 /*
26 * Here, mutex is required to serialize the calls to del_wk work between
27 * user/kernel space which happens when devcd is added with device_add()
28 * and that sends uevent to user space. User space reads the uevents,
29 * and calls to devcd_data_write() which try to modify the work which is
30 * not even initialized/queued from devcoredump.
31 *
32 *
33 *
34 * cpu0(X) cpu1(Y)
35 *
36 * dev_coredump() uevent sent to user space
37 * device_add() ======================> user space process Y reads the
38 * uevents writes to devcd fd
39 * which results into writes to
40 *
41 * devcd_data_write()
42 * mod_delayed_work()
43 * try_to_grab_pending()
44 * del_timer()
45 * debug_assert_init()
46 * INIT_DELAYED_WORK()
47 * schedule_delayed_work()
48 *
49 *
50 * Also, mutex alone would not be enough to avoid scheduling of
51 * del_wk work after it get flush from a call to devcd_free()
52 * mentioned as below.
53 *
54 * disabled_store()
55 * devcd_free()
56 * mutex_lock() devcd_data_write()
57 * flush_delayed_work()
58 * mutex_unlock()
59 * mutex_lock()
60 * mod_delayed_work()
61 * mutex_unlock()
62 * So, delete_work flag is required.
63 */
64 struct mutex mutex;
65 bool delete_work;
66 struct module *owner;
67 ssize_t (*read)(char *buffer, loff_t offset, size_t count,
68 void *data, size_t datalen);
69 void (*free)(void *data);
70 struct delayed_work del_wk;
71 struct device *failing_dev;
72};
73
74static struct devcd_entry *dev_to_devcd(struct device *dev)
75{
76 return container_of(dev, struct devcd_entry, devcd_dev);
77}
78
79static void devcd_dev_release(struct device *dev)
80{
81 struct devcd_entry *devcd = dev_to_devcd(dev);
82
83 devcd->free(devcd->data);
84 module_put(devcd->owner);
85
86 /*
87 * this seems racy, but I don't see a notifier or such on
88 * a struct device to know when it goes away?
89 */
90 if (devcd->failing_dev->kobj.sd)
91 sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
92 "devcoredump");
93
94 put_device(devcd->failing_dev);
95 kfree(devcd);
96}
97
98static void devcd_del(struct work_struct *wk)
99{
100 struct devcd_entry *devcd;
101
102 devcd = container_of(wk, struct devcd_entry, del_wk.work);
103
104 device_del(&devcd->devcd_dev);
105 put_device(&devcd->devcd_dev);
106}
107
108static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj,
109 struct bin_attribute *bin_attr,
110 char *buffer, loff_t offset, size_t count)
111{
112 struct device *dev = kobj_to_dev(kobj);
113 struct devcd_entry *devcd = dev_to_devcd(dev);
114
115 return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
116}
117
118static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj,
119 struct bin_attribute *bin_attr,
120 char *buffer, loff_t offset, size_t count)
121{
122 struct device *dev = kobj_to_dev(kobj);
123 struct devcd_entry *devcd = dev_to_devcd(dev);
124
125 mutex_lock(&devcd->mutex);
126 if (!devcd->delete_work) {
127 devcd->delete_work = true;
128 mod_delayed_work(system_wq, &devcd->del_wk, 0);
129 }
130 mutex_unlock(&devcd->mutex);
131
132 return count;
133}
134
135static struct bin_attribute devcd_attr_data = {
136 .attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, },
137 .size = 0,
138 .read = devcd_data_read,
139 .write = devcd_data_write,
140};
141
142static struct bin_attribute *devcd_dev_bin_attrs[] = {
143 &devcd_attr_data, NULL,
144};
145
146static const struct attribute_group devcd_dev_group = {
147 .bin_attrs = devcd_dev_bin_attrs,
148};
149
150static const struct attribute_group *devcd_dev_groups[] = {
151 &devcd_dev_group, NULL,
152};
153
154static int devcd_free(struct device *dev, void *data)
155{
156 struct devcd_entry *devcd = dev_to_devcd(dev);
157
158 mutex_lock(&devcd->mutex);
159 if (!devcd->delete_work)
160 devcd->delete_work = true;
161
162 flush_delayed_work(&devcd->del_wk);
163 mutex_unlock(&devcd->mutex);
164 return 0;
165}
166
167static ssize_t disabled_show(const struct class *class, const struct class_attribute *attr,
168 char *buf)
169{
170 return sysfs_emit(buf, "%d\n", devcd_disabled);
171}
172
173/*
174 *
175 * disabled_store() worker()
176 * class_for_each_device(&devcd_class,
177 * NULL, NULL, devcd_free)
178 * ...
179 * ...
180 * while ((dev = class_dev_iter_next(&iter))
181 * devcd_del()
182 * device_del()
183 * put_device() <- last reference
184 * error = fn(dev, data) devcd_dev_release()
185 * devcd_free(dev, data) kfree(devcd)
186 * mutex_lock(&devcd->mutex);
187 *
188 *
189 * In the above diagram, It looks like disabled_store() would be racing with parallely
190 * running devcd_del() and result in memory abort while acquiring devcd->mutex which
191 * is called after kfree of devcd memory after dropping its last reference with
192 * put_device(). However, this will not happens as fn(dev, data) runs
193 * with its own reference to device via klist_node so it is not its last reference.
194 * so, above situation would not occur.
195 */
196
197static ssize_t disabled_store(const struct class *class, const struct class_attribute *attr,
198 const char *buf, size_t count)
199{
200 long tmp = simple_strtol(buf, NULL, 10);
201
202 /*
203 * This essentially makes the attribute write-once, since you can't
204 * go back to not having it disabled. This is intentional, it serves
205 * as a system lockdown feature.
206 */
207 if (tmp != 1)
208 return -EINVAL;
209
210 devcd_disabled = true;
211
212 class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
213
214 return count;
215}
216static CLASS_ATTR_RW(disabled);
217
218static struct attribute *devcd_class_attrs[] = {
219 &class_attr_disabled.attr,
220 NULL,
221};
222ATTRIBUTE_GROUPS(devcd_class);
223
224static struct class devcd_class = {
225 .name = "devcoredump",
226 .dev_release = devcd_dev_release,
227 .dev_groups = devcd_dev_groups,
228 .class_groups = devcd_class_groups,
229};
230
231static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
232 void *data, size_t datalen)
233{
234 return memory_read_from_buffer(buffer, count, &offset, data, datalen);
235}
236
237static void devcd_freev(void *data)
238{
239 vfree(data);
240}
241
242/**
243 * dev_coredumpv - create device coredump with vmalloc data
244 * @dev: the struct device for the crashed device
245 * @data: vmalloc data containing the device coredump
246 * @datalen: length of the data
247 * @gfp: allocation flags
248 *
249 * This function takes ownership of the vmalloc'ed data and will free
250 * it when it is no longer used. See dev_coredumpm() for more information.
251 */
252void dev_coredumpv(struct device *dev, void *data, size_t datalen,
253 gfp_t gfp)
254{
255 dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
256}
257EXPORT_SYMBOL_GPL(dev_coredumpv);
258
259static int devcd_match_failing(struct device *dev, const void *failing)
260{
261 struct devcd_entry *devcd = dev_to_devcd(dev);
262
263 return devcd->failing_dev == failing;
264}
265
266/**
267 * devcd_free_sgtable - free all the memory of the given scatterlist table
268 * (i.e. both pages and scatterlist instances)
269 * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
270 * using the sg_chain function then that function should be called only once
271 * on the chained table
272 * @data: pointer to sg_table to free
273 */
274static void devcd_free_sgtable(void *data)
275{
276 _devcd_free_sgtable(data);
277}
278
279/**
280 * devcd_read_from_sgtable - copy data from sg_table to a given buffer
281 * and return the number of bytes read
282 * @buffer: the buffer to copy the data to it
283 * @buf_len: the length of the buffer
284 * @data: the scatterlist table to copy from
285 * @offset: start copy from @offset@ bytes from the head of the data
286 * in the given scatterlist
287 * @data_len: the length of the data in the sg_table
288 */
289static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
290 size_t buf_len, void *data,
291 size_t data_len)
292{
293 struct scatterlist *table = data;
294
295 if (offset > data_len)
296 return -EINVAL;
297
298 if (offset + buf_len > data_len)
299 buf_len = data_len - offset;
300 return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
301 offset);
302}
303
304/**
305 * dev_coredump_put - remove device coredump
306 * @dev: the struct device for the crashed device
307 *
308 * dev_coredump_put() removes coredump, if exists, for a given device from
309 * the file system and free its associated data otherwise, does nothing.
310 *
311 * It is useful for modules that do not want to keep coredump
312 * available after its unload.
313 */
314void dev_coredump_put(struct device *dev)
315{
316 struct device *existing;
317
318 existing = class_find_device(&devcd_class, NULL, dev,
319 devcd_match_failing);
320 if (existing) {
321 devcd_free(existing, NULL);
322 put_device(existing);
323 }
324}
325EXPORT_SYMBOL_GPL(dev_coredump_put);
326
327/**
328 * dev_coredumpm_timeout - create device coredump with read/free methods with a
329 * custom timeout.
330 * @dev: the struct device for the crashed device
331 * @owner: the module that contains the read/free functions, use %THIS_MODULE
332 * @data: data cookie for the @read/@free functions
333 * @datalen: length of the data
334 * @gfp: allocation flags
335 * @read: function to read from the given buffer
336 * @free: function to free the given buffer
337 * @timeout: time in jiffies to remove coredump
338 *
339 * Creates a new device coredump for the given device. If a previous one hasn't
340 * been read yet, the new coredump is discarded. The data lifetime is determined
341 * by the device coredump framework and when it is no longer needed the @free
342 * function will be called to free the data.
343 */
344void dev_coredumpm_timeout(struct device *dev, struct module *owner,
345 void *data, size_t datalen, gfp_t gfp,
346 ssize_t (*read)(char *buffer, loff_t offset,
347 size_t count, void *data,
348 size_t datalen),
349 void (*free)(void *data),
350 unsigned long timeout)
351{
352 static atomic_t devcd_count = ATOMIC_INIT(0);
353 struct devcd_entry *devcd;
354 struct device *existing;
355
356 if (devcd_disabled)
357 goto free;
358
359 existing = class_find_device(&devcd_class, NULL, dev,
360 devcd_match_failing);
361 if (existing) {
362 put_device(existing);
363 goto free;
364 }
365
366 if (!try_module_get(owner))
367 goto free;
368
369 devcd = kzalloc(sizeof(*devcd), gfp);
370 if (!devcd)
371 goto put_module;
372
373 devcd->owner = owner;
374 devcd->data = data;
375 devcd->datalen = datalen;
376 devcd->read = read;
377 devcd->free = free;
378 devcd->failing_dev = get_device(dev);
379 devcd->delete_work = false;
380
381 mutex_init(&devcd->mutex);
382 device_initialize(&devcd->devcd_dev);
383
384 dev_set_name(&devcd->devcd_dev, "devcd%d",
385 atomic_inc_return(&devcd_count));
386 devcd->devcd_dev.class = &devcd_class;
387
388 mutex_lock(&devcd->mutex);
389 dev_set_uevent_suppress(&devcd->devcd_dev, true);
390 if (device_add(&devcd->devcd_dev))
391 goto put_device;
392
393 /*
394 * These should normally not fail, but there is no problem
395 * continuing without the links, so just warn instead of
396 * failing.
397 */
398 if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
399 "failing_device") ||
400 sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
401 "devcoredump"))
402 dev_warn(dev, "devcoredump create_link failed\n");
403
404 dev_set_uevent_suppress(&devcd->devcd_dev, false);
405 kobject_uevent(&devcd->devcd_dev.kobj, KOBJ_ADD);
406 INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
407 schedule_delayed_work(&devcd->del_wk, timeout);
408 mutex_unlock(&devcd->mutex);
409 return;
410 put_device:
411 put_device(&devcd->devcd_dev);
412 mutex_unlock(&devcd->mutex);
413 put_module:
414 module_put(owner);
415 free:
416 free(data);
417}
418EXPORT_SYMBOL_GPL(dev_coredumpm_timeout);
419
420/**
421 * dev_coredumpsg - create device coredump that uses scatterlist as data
422 * parameter
423 * @dev: the struct device for the crashed device
424 * @table: the dump data
425 * @datalen: length of the data
426 * @gfp: allocation flags
427 *
428 * Creates a new device coredump for the given device. If a previous one hasn't
429 * been read yet, the new coredump is discarded. The data lifetime is determined
430 * by the device coredump framework and when it is no longer needed
431 * it will free the data.
432 */
433void dev_coredumpsg(struct device *dev, struct scatterlist *table,
434 size_t datalen, gfp_t gfp)
435{
436 dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
437 devcd_free_sgtable);
438}
439EXPORT_SYMBOL_GPL(dev_coredumpsg);
440
441static int __init devcoredump_init(void)
442{
443 return class_register(&devcd_class);
444}
445__initcall(devcoredump_init);
446
447static void __exit devcoredump_exit(void)
448{
449 class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
450 class_unregister(&devcd_class);
451}
452__exitcall(devcoredump_exit);