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989d42e8 | 1 | // SPDX-License-Identifier: GPL-2.0 |
833c9545 | 2 | /* |
833c9545 | 3 | * Copyright(c) 2014 Intel Mobile Communications GmbH |
52256637 | 4 | * Copyright(c) 2015 Intel Deutschland GmbH |
833c9545 | 5 | * |
833c9545 JB |
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 | ||
d4533329 JB |
16 | static struct class devcd_class; |
17 | ||
18 | /* global disable flag, for security purposes */ | |
19 | static bool devcd_disabled; | |
20 | ||
833c9545 JB |
21 | /* if data isn't read by userspace after 5 minutes then delete it */ |
22 | #define DEVCD_TIMEOUT (HZ * 60 * 5) | |
23 | ||
24 | struct devcd_entry { | |
25 | struct device devcd_dev; | |
52256637 | 26 | void *data; |
833c9545 | 27 | size_t datalen; |
01daccf7 MO |
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; | |
833c9545 JB |
69 | struct module *owner; |
70 | ssize_t (*read)(char *buffer, loff_t offset, size_t count, | |
52256637 AE |
71 | void *data, size_t datalen); |
72 | void (*free)(void *data); | |
833c9545 JB |
73 | struct delayed_work del_wk; |
74 | struct device *failing_dev; | |
75 | }; | |
76 | ||
77 | static struct devcd_entry *dev_to_devcd(struct device *dev) | |
78 | { | |
79 | return container_of(dev, struct devcd_entry, devcd_dev); | |
80 | } | |
81 | ||
82 | static 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 | ||
101 | static 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 | ||
111 | static 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 | ||
121 | static 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 | ||
01daccf7 MO |
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); | |
833c9545 JB |
134 | |
135 | return count; | |
136 | } | |
137 | ||
138 | static 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 | ||
145 | static struct bin_attribute *devcd_dev_bin_attrs[] = { | |
146 | &devcd_attr_data, NULL, | |
147 | }; | |
148 | ||
149 | static const struct attribute_group devcd_dev_group = { | |
150 | .bin_attrs = devcd_dev_bin_attrs, | |
151 | }; | |
152 | ||
153 | static const struct attribute_group *devcd_dev_groups[] = { | |
154 | &devcd_dev_group, NULL, | |
155 | }; | |
156 | ||
d4533329 JB |
157 | static int devcd_free(struct device *dev, void *data) |
158 | { | |
159 | struct devcd_entry *devcd = dev_to_devcd(dev); | |
160 | ||
01daccf7 MO |
161 | mutex_lock(&devcd->mutex); |
162 | if (!devcd->delete_work) | |
163 | devcd->delete_work = true; | |
164 | ||
d4533329 | 165 | flush_delayed_work(&devcd->del_wk); |
01daccf7 | 166 | mutex_unlock(&devcd->mutex); |
d4533329 JB |
167 | return 0; |
168 | } | |
169 | ||
170 | static ssize_t disabled_show(struct class *class, struct class_attribute *attr, | |
171 | char *buf) | |
172 | { | |
948b3edb | 173 | return sysfs_emit(buf, "%d\n", devcd_disabled); |
d4533329 JB |
174 | } |
175 | ||
01daccf7 MO |
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 | ||
d4533329 JB |
200 | static 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 | } | |
f76d2527 | 219 | static CLASS_ATTR_RW(disabled); |
d4533329 | 220 | |
f76d2527 GKH |
221 | static struct attribute *devcd_class_attrs[] = { |
222 | &class_attr_disabled.attr, | |
223 | NULL, | |
d4533329 | 224 | }; |
f76d2527 | 225 | ATTRIBUTE_GROUPS(devcd_class); |
d4533329 | 226 | |
833c9545 JB |
227 | static struct class devcd_class = { |
228 | .name = "devcoredump", | |
229 | .owner = THIS_MODULE, | |
230 | .dev_release = devcd_dev_release, | |
231 | .dev_groups = devcd_dev_groups, | |
f76d2527 | 232 | .class_groups = devcd_class_groups, |
833c9545 JB |
233 | }; |
234 | ||
235 | static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count, | |
52256637 | 236 | void *data, size_t datalen) |
833c9545 | 237 | { |
ce684d95 | 238 | return memory_read_from_buffer(buffer, count, &offset, data, datalen); |
833c9545 JB |
239 | } |
240 | ||
52256637 AE |
241 | static void devcd_freev(void *data) |
242 | { | |
243 | vfree(data); | |
244 | } | |
245 | ||
833c9545 JB |
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 | */ | |
52256637 | 256 | void dev_coredumpv(struct device *dev, void *data, size_t datalen, |
833c9545 JB |
257 | gfp_t gfp) |
258 | { | |
52256637 | 259 | dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev); |
833c9545 JB |
260 | } |
261 | EXPORT_SYMBOL_GPL(dev_coredumpv); | |
262 | ||
263 | static 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 | ||
52256637 AE |
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 | |
cc710790 | 276 | * @data: pointer to sg_table to free |
52256637 AE |
277 | */ |
278 | static void devcd_free_sgtable(void *data) | |
279 | { | |
280 | _devcd_free_sgtable(data); | |
281 | } | |
282 | ||
283 | /** | |
cc710790 | 284 | * devcd_read_from_sgtable - copy data from sg_table to a given buffer |
52256637 AE |
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 | */ | |
293 | static 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 | ||
833c9545 JB |
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 | */ | |
323 | void dev_coredumpm(struct device *dev, struct module *owner, | |
52256637 | 324 | void *data, size_t datalen, gfp_t gfp, |
833c9545 | 325 | ssize_t (*read)(char *buffer, loff_t offset, size_t count, |
52256637 AE |
326 | void *data, size_t datalen), |
327 | void (*free)(void *data)) | |
833c9545 JB |
328 | { |
329 | static atomic_t devcd_count = ATOMIC_INIT(0); | |
330 | struct devcd_entry *devcd; | |
331 | struct device *existing; | |
332 | ||
d4533329 JB |
333 | if (devcd_disabled) |
334 | goto free; | |
335 | ||
833c9545 JB |
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); | |
01daccf7 | 356 | devcd->delete_work = false; |
833c9545 | 357 | |
01daccf7 | 358 | mutex_init(&devcd->mutex); |
833c9545 JB |
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 | ||
01daccf7 | 365 | mutex_lock(&devcd->mutex); |
833c9545 JB |
366 | if (device_add(&devcd->devcd_dev)) |
367 | goto put_device; | |
368 | ||
53f95c55 AB |
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 | */ | |
833c9545 | 374 | if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj, |
53f95c55 AB |
375 | "failing_device") || |
376 | sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj, | |
377 | "devcoredump")) | |
378 | dev_warn(dev, "devcoredump create_link failed\n"); | |
833c9545 JB |
379 | |
380 | INIT_DELAYED_WORK(&devcd->del_wk, devcd_del); | |
381 | schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT); | |
01daccf7 | 382 | mutex_unlock(&devcd->mutex); |
833c9545 JB |
383 | return; |
384 | put_device: | |
385 | put_device(&devcd->devcd_dev); | |
01daccf7 | 386 | mutex_unlock(&devcd->mutex); |
833c9545 JB |
387 | put_module: |
388 | module_put(owner); | |
389 | free: | |
390 | free(data); | |
391 | } | |
392 | EXPORT_SYMBOL_GPL(dev_coredumpm); | |
393 | ||
52256637 | 394 | /** |
2a77eec0 | 395 | * dev_coredumpsg - create device coredump that uses scatterlist as data |
52256637 AE |
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 | */ | |
407 | void 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 | } | |
413 | EXPORT_SYMBOL_GPL(dev_coredumpsg); | |
414 | ||
833c9545 JB |
415 | static int __init devcoredump_init(void) |
416 | { | |
417 | return class_register(&devcd_class); | |
418 | } | |
419 | __initcall(devcoredump_init); | |
420 | ||
833c9545 JB |
421 | static 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); |