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