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 * Contact Information:
7 * Intel Linux Wireless <ilw@linux.intel.com>
8 * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
9 *
10 * Author: Johannes Berg <johannes@sipsolutions.net>
11 */
12 #include <linux/module.h>
13 #include <linux/device.h>
14 #include <linux/devcoredump.h>
15 #include <linux/list.h>
16 #include <linux/slab.h>
17 #include <linux/fs.h>
18 #include <linux/workqueue.h>
19
20 static struct class devcd_class;
21
22 /* global disable flag, for security purposes */
23 static bool devcd_disabled;
24
25 /* if data isn't read by userspace after 5 minutes then delete it */
26 #define DEVCD_TIMEOUT (HZ * 60 * 5)
27
28 struct devcd_entry {
29 struct device devcd_dev;
30 void *data;
31 size_t datalen;
32 /*
33 * Here, mutex is required to serialize the calls to del_wk work between
34 * user/kernel space which happens when devcd is added with device_add()
35 * and that sends uevent to user space. User space reads the uevents,
36 * and calls to devcd_data_write() which try to modify the work which is
37 * not even initialized/queued from devcoredump.
38 *
39 *
40 *
41 * cpu0(X) cpu1(Y)
42 *
43 * dev_coredump() uevent sent to user space
44 * device_add() ======================> user space process Y reads the
45 * uevents writes to devcd fd
46 * which results into writes to
47 *
48 * devcd_data_write()
49 * mod_delayed_work()
50 * try_to_grab_pending()
51 * del_timer()
52 * debug_assert_init()
53 * INIT_DELAYED_WORK()
54 * schedule_delayed_work()
55 *
56 *
57 * Also, mutex alone would not be enough to avoid scheduling of
58 * del_wk work after it get flush from a call to devcd_free()
59 * mentioned as below.
60 *
61 * disabled_store()
62 * devcd_free()
63 * mutex_lock() devcd_data_write()
64 * flush_delayed_work()
65 * mutex_unlock()
66 * mutex_lock()
67 * mod_delayed_work()
68 * mutex_unlock()
69 * So, delete_work flag is required.
70 */
71 struct mutex mutex;
72 bool delete_work;
73 struct module *owner;
74 ssize_t (*read)(char *buffer, loff_t offset, size_t count,
75 void *data, size_t datalen);
76 void (*free)(void *data);
77 struct delayed_work del_wk;
78 struct device *failing_dev;
79 };
80
dev_to_devcd(struct device * dev)81 static struct devcd_entry *dev_to_devcd(struct device *dev)
82 {
83 return container_of(dev, struct devcd_entry, devcd_dev);
84 }
85
devcd_dev_release(struct device * dev)86 static void devcd_dev_release(struct device *dev)
87 {
88 struct devcd_entry *devcd = dev_to_devcd(dev);
89
90 devcd->free(devcd->data);
91 module_put(devcd->owner);
92
93 /*
94 * this seems racy, but I don't see a notifier or such on
95 * a struct device to know when it goes away?
96 */
97 if (devcd->failing_dev->kobj.sd)
98 sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
99 "devcoredump");
100
101 put_device(devcd->failing_dev);
102 kfree(devcd);
103 }
104
devcd_del(struct work_struct * wk)105 static void devcd_del(struct work_struct *wk)
106 {
107 struct devcd_entry *devcd;
108
109 devcd = container_of(wk, struct devcd_entry, del_wk.work);
110
111 device_del(&devcd->devcd_dev);
112 put_device(&devcd->devcd_dev);
113 }
114
devcd_data_read(struct file * filp,struct kobject * kobj,struct bin_attribute * bin_attr,char * buffer,loff_t offset,size_t count)115 static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj,
116 struct bin_attribute *bin_attr,
117 char *buffer, loff_t offset, size_t count)
118 {
119 struct device *dev = kobj_to_dev(kobj);
120 struct devcd_entry *devcd = dev_to_devcd(dev);
121
122 return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
123 }
124
devcd_data_write(struct file * filp,struct kobject * kobj,struct bin_attribute * bin_attr,char * buffer,loff_t offset,size_t count)125 static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj,
126 struct bin_attribute *bin_attr,
127 char *buffer, loff_t offset, size_t count)
128 {
129 struct device *dev = kobj_to_dev(kobj);
130 struct devcd_entry *devcd = dev_to_devcd(dev);
131
132 mutex_lock(&devcd->mutex);
133 if (!devcd->delete_work) {
134 devcd->delete_work = true;
135 mod_delayed_work(system_wq, &devcd->del_wk, 0);
136 }
137 mutex_unlock(&devcd->mutex);
138
139 return count;
140 }
141
142 static struct bin_attribute devcd_attr_data = {
143 .attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, },
144 .size = 0,
145 .read = devcd_data_read,
146 .write = devcd_data_write,
147 };
148
149 static struct bin_attribute *devcd_dev_bin_attrs[] = {
150 &devcd_attr_data, NULL,
151 };
152
153 static const struct attribute_group devcd_dev_group = {
154 .bin_attrs = devcd_dev_bin_attrs,
155 };
156
157 static const struct attribute_group *devcd_dev_groups[] = {
158 &devcd_dev_group, NULL,
159 };
160
devcd_free(struct device * dev,void * data)161 static int devcd_free(struct device *dev, void *data)
162 {
163 struct devcd_entry *devcd = dev_to_devcd(dev);
164
165 mutex_lock(&devcd->mutex);
166 if (!devcd->delete_work)
167 devcd->delete_work = true;
168
169 flush_delayed_work(&devcd->del_wk);
170 mutex_unlock(&devcd->mutex);
171 return 0;
172 }
173
disabled_show(struct class * class,struct class_attribute * attr,char * buf)174 static ssize_t disabled_show(struct class *class, struct class_attribute *attr,
175 char *buf)
176 {
177 return sysfs_emit(buf, "%d\n", devcd_disabled);
178 }
179
180 /*
181 *
182 * disabled_store() worker()
183 * class_for_each_device(&devcd_class,
184 * NULL, NULL, devcd_free)
185 * ...
186 * ...
187 * while ((dev = class_dev_iter_next(&iter))
188 * devcd_del()
189 * device_del()
190 * put_device() <- last reference
191 * error = fn(dev, data) devcd_dev_release()
192 * devcd_free(dev, data) kfree(devcd)
193 * mutex_lock(&devcd->mutex);
194 *
195 *
196 * In the above diagram, It looks like disabled_store() would be racing with parallely
197 * running devcd_del() and result in memory abort while acquiring devcd->mutex which
198 * is called after kfree of devcd memory after dropping its last reference with
199 * put_device(). However, this will not happens as fn(dev, data) runs
200 * with its own reference to device via klist_node so it is not its last reference.
201 * so, above situation would not occur.
202 */
203
disabled_store(struct class * class,struct class_attribute * attr,const char * buf,size_t count)204 static ssize_t disabled_store(struct class *class, struct class_attribute *attr,
205 const char *buf, size_t count)
206 {
207 long tmp = simple_strtol(buf, NULL, 10);
208
209 /*
210 * This essentially makes the attribute write-once, since you can't
211 * go back to not having it disabled. This is intentional, it serves
212 * as a system lockdown feature.
213 */
214 if (tmp != 1)
215 return -EINVAL;
216
217 devcd_disabled = true;
218
219 class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
220
221 return count;
222 }
223 static CLASS_ATTR_RW(disabled);
224
225 static struct attribute *devcd_class_attrs[] = {
226 &class_attr_disabled.attr,
227 NULL,
228 };
229 ATTRIBUTE_GROUPS(devcd_class);
230
231 static struct class devcd_class = {
232 .name = "devcoredump",
233 .owner = THIS_MODULE,
234 .dev_release = devcd_dev_release,
235 .dev_groups = devcd_dev_groups,
236 .class_groups = devcd_class_groups,
237 };
238
devcd_readv(char * buffer,loff_t offset,size_t count,void * data,size_t datalen)239 static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
240 void *data, size_t datalen)
241 {
242 return memory_read_from_buffer(buffer, count, &offset, data, datalen);
243 }
244
devcd_freev(void * data)245 static void devcd_freev(void *data)
246 {
247 vfree(data);
248 }
249
250 /**
251 * dev_coredumpv - create device coredump with vmalloc data
252 * @dev: the struct device for the crashed device
253 * @data: vmalloc data containing the device coredump
254 * @datalen: length of the data
255 * @gfp: allocation flags
256 *
257 * This function takes ownership of the vmalloc'ed data and will free
258 * it when it is no longer used. See dev_coredumpm() for more information.
259 */
dev_coredumpv(struct device * dev,void * data,size_t datalen,gfp_t gfp)260 void dev_coredumpv(struct device *dev, void *data, size_t datalen,
261 gfp_t gfp)
262 {
263 dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
264 }
265 EXPORT_SYMBOL_GPL(dev_coredumpv);
266
devcd_match_failing(struct device * dev,const void * failing)267 static int devcd_match_failing(struct device *dev, const void *failing)
268 {
269 struct devcd_entry *devcd = dev_to_devcd(dev);
270
271 return devcd->failing_dev == failing;
272 }
273
274 /**
275 * devcd_free_sgtable - free all the memory of the given scatterlist table
276 * (i.e. both pages and scatterlist instances)
277 * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
278 * using the sg_chain function then that function should be called only once
279 * on the chained table
280 * @table: pointer to sg_table to free
281 */
devcd_free_sgtable(void * data)282 static void devcd_free_sgtable(void *data)
283 {
284 _devcd_free_sgtable(data);
285 }
286
287 /**
288 * devcd_read_from_table - copy data from sg_table to a given buffer
289 * and return the number of bytes read
290 * @buffer: the buffer to copy the data to it
291 * @buf_len: the length of the buffer
292 * @data: the scatterlist table to copy from
293 * @offset: start copy from @offset@ bytes from the head of the data
294 * in the given scatterlist
295 * @data_len: the length of the data in the sg_table
296 */
devcd_read_from_sgtable(char * buffer,loff_t offset,size_t buf_len,void * data,size_t data_len)297 static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
298 size_t buf_len, void *data,
299 size_t data_len)
300 {
301 struct scatterlist *table = data;
302
303 if (offset > data_len)
304 return -EINVAL;
305
306 if (offset + buf_len > data_len)
307 buf_len = data_len - offset;
308 return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
309 offset);
310 }
311
312 /**
313 * dev_coredumpm - create device coredump with read/free methods
314 * @dev: the struct device for the crashed device
315 * @owner: the module that contains the read/free functions, use %THIS_MODULE
316 * @data: data cookie for the @read/@free functions
317 * @datalen: length of the data
318 * @gfp: allocation flags
319 * @read: function to read from the given buffer
320 * @free: function to free the given buffer
321 *
322 * Creates a new device coredump for the given device. If a previous one hasn't
323 * been read yet, the new coredump is discarded. The data lifetime is determined
324 * by the device coredump framework and when it is no longer needed the @free
325 * function will be called to free the data.
326 */
dev_coredumpm(struct device * dev,struct module * owner,void * data,size_t datalen,gfp_t gfp,ssize_t (* read)(char * buffer,loff_t offset,size_t count,void * data,size_t datalen),void (* free)(void * data))327 void dev_coredumpm(struct device *dev, struct module *owner,
328 void *data, size_t datalen, gfp_t gfp,
329 ssize_t (*read)(char *buffer, loff_t offset, size_t count,
330 void *data, size_t datalen),
331 void (*free)(void *data))
332 {
333 static atomic_t devcd_count = ATOMIC_INIT(0);
334 struct devcd_entry *devcd;
335 struct device *existing;
336
337 if (devcd_disabled)
338 goto free;
339
340 existing = class_find_device(&devcd_class, NULL, dev,
341 devcd_match_failing);
342 if (existing) {
343 put_device(existing);
344 goto free;
345 }
346
347 if (!try_module_get(owner))
348 goto free;
349
350 devcd = kzalloc(sizeof(*devcd), gfp);
351 if (!devcd)
352 goto put_module;
353
354 devcd->owner = owner;
355 devcd->data = data;
356 devcd->datalen = datalen;
357 devcd->read = read;
358 devcd->free = free;
359 devcd->failing_dev = get_device(dev);
360 devcd->delete_work = false;
361
362 mutex_init(&devcd->mutex);
363 device_initialize(&devcd->devcd_dev);
364
365 dev_set_name(&devcd->devcd_dev, "devcd%d",
366 atomic_inc_return(&devcd_count));
367 devcd->devcd_dev.class = &devcd_class;
368
369 mutex_lock(&devcd->mutex);
370 dev_set_uevent_suppress(&devcd->devcd_dev, true);
371 if (device_add(&devcd->devcd_dev))
372 goto put_device;
373
374 if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
375 "failing_device"))
376 /* nothing - symlink will be missing */;
377
378 if (sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
379 "devcoredump"))
380 /* nothing - symlink will be missing */;
381
382 dev_set_uevent_suppress(&devcd->devcd_dev, false);
383 kobject_uevent(&devcd->devcd_dev.kobj, KOBJ_ADD);
384 INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
385 schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
386 mutex_unlock(&devcd->mutex);
387 return;
388 put_device:
389 put_device(&devcd->devcd_dev);
390 mutex_unlock(&devcd->mutex);
391 put_module:
392 module_put(owner);
393 free:
394 free(data);
395 }
396 EXPORT_SYMBOL_GPL(dev_coredumpm);
397
398 /**
399 * dev_coredumpsg - create device coredump that uses scatterlist as data
400 * parameter
401 * @dev: the struct device for the crashed device
402 * @table: the dump data
403 * @datalen: length of the data
404 * @gfp: allocation flags
405 *
406 * Creates a new device coredump for the given device. If a previous one hasn't
407 * been read yet, the new coredump is discarded. The data lifetime is determined
408 * by the device coredump framework and when it is no longer needed
409 * it will free the data.
410 */
dev_coredumpsg(struct device * dev,struct scatterlist * table,size_t datalen,gfp_t gfp)411 void dev_coredumpsg(struct device *dev, struct scatterlist *table,
412 size_t datalen, gfp_t gfp)
413 {
414 dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
415 devcd_free_sgtable);
416 }
417 EXPORT_SYMBOL_GPL(dev_coredumpsg);
418
devcoredump_init(void)419 static int __init devcoredump_init(void)
420 {
421 return class_register(&devcd_class);
422 }
423 __initcall(devcoredump_init);
424
devcoredump_exit(void)425 static void __exit devcoredump_exit(void)
426 {
427 class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
428 class_unregister(&devcd_class);
429 }
430 __exitcall(devcoredump_exit);
431