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 | |
16 | static struct class devcd_class; |
17 | |
18 | /* global disable flag, for security purposes */ |
19 | static 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 | |
24 | struct 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 | |
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(module: 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(dir: &devcd->failing_dev->kobj, targ: &dev->kobj, |
95 | name: "devcoredump" ); |
96 | |
97 | put_device(dev: devcd->failing_dev); |
98 | kfree(objp: 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(dev: &devcd->devcd_dev); |
108 | put_device(dev: &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 | |
128 | mutex_lock(&devcd->mutex); |
129 | if (!devcd->delete_work) { |
130 | devcd->delete_work = true; |
131 | mod_delayed_work(wq: system_wq, dwork: &devcd->del_wk, delay: 0); |
132 | } |
133 | mutex_unlock(lock: &devcd->mutex); |
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 | |
157 | static 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(dwork: &devcd->del_wk); |
166 | mutex_unlock(lock: &devcd->mutex); |
167 | return 0; |
168 | } |
169 | |
170 | static ssize_t disabled_show(const struct class *class, const struct class_attribute *attr, |
171 | char *buf) |
172 | { |
173 | return sysfs_emit(buf, fmt: "%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 | |
200 | static ssize_t disabled_store(const struct class *class, const 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(class: &devcd_class, NULL, NULL, fn: devcd_free); |
216 | |
217 | return count; |
218 | } |
219 | static CLASS_ATTR_RW(disabled); |
220 | |
221 | static struct attribute *devcd_class_attrs[] = { |
222 | &class_attr_disabled.attr, |
223 | NULL, |
224 | }; |
225 | ATTRIBUTE_GROUPS(devcd_class); |
226 | |
227 | static struct class devcd_class = { |
228 | .name = "devcoredump" , |
229 | .dev_release = devcd_dev_release, |
230 | .dev_groups = devcd_dev_groups, |
231 | .class_groups = devcd_class_groups, |
232 | }; |
233 | |
234 | static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count, |
235 | void *data, size_t datalen) |
236 | { |
237 | return memory_read_from_buffer(to: buffer, count, ppos: &offset, from: data, available: datalen); |
238 | } |
239 | |
240 | static void devcd_freev(void *data) |
241 | { |
242 | vfree(addr: data); |
243 | } |
244 | |
245 | /** |
246 | * dev_coredumpv - create device coredump with vmalloc data |
247 | * @dev: the struct device for the crashed device |
248 | * @data: vmalloc data containing the device coredump |
249 | * @datalen: length of the data |
250 | * @gfp: allocation flags |
251 | * |
252 | * This function takes ownership of the vmalloc'ed data and will free |
253 | * it when it is no longer used. See dev_coredumpm() for more information. |
254 | */ |
255 | void dev_coredumpv(struct device *dev, void *data, size_t datalen, |
256 | gfp_t gfp) |
257 | { |
258 | dev_coredumpm(dev, NULL, data, datalen, gfp, read: devcd_readv, free: devcd_freev); |
259 | } |
260 | EXPORT_SYMBOL_GPL(dev_coredumpv); |
261 | |
262 | static int devcd_match_failing(struct device *dev, const void *failing) |
263 | { |
264 | struct devcd_entry *devcd = dev_to_devcd(dev); |
265 | |
266 | return devcd->failing_dev == failing; |
267 | } |
268 | |
269 | /** |
270 | * devcd_free_sgtable - free all the memory of the given scatterlist table |
271 | * (i.e. both pages and scatterlist instances) |
272 | * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained |
273 | * using the sg_chain function then that function should be called only once |
274 | * on the chained table |
275 | * @data: pointer to sg_table to free |
276 | */ |
277 | static void devcd_free_sgtable(void *data) |
278 | { |
279 | _devcd_free_sgtable(table: data); |
280 | } |
281 | |
282 | /** |
283 | * devcd_read_from_sgtable - copy data from sg_table to a given buffer |
284 | * and return the number of bytes read |
285 | * @buffer: the buffer to copy the data to it |
286 | * @buf_len: the length of the buffer |
287 | * @data: the scatterlist table to copy from |
288 | * @offset: start copy from @offset@ bytes from the head of the data |
289 | * in the given scatterlist |
290 | * @data_len: the length of the data in the sg_table |
291 | */ |
292 | static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset, |
293 | size_t buf_len, void *data, |
294 | size_t data_len) |
295 | { |
296 | struct scatterlist *table = data; |
297 | |
298 | if (offset > data_len) |
299 | return -EINVAL; |
300 | |
301 | if (offset + buf_len > data_len) |
302 | buf_len = data_len - offset; |
303 | return sg_pcopy_to_buffer(sgl: table, nents: sg_nents(sg: table), buf: buffer, buflen: buf_len, |
304 | skip: offset); |
305 | } |
306 | |
307 | /** |
308 | * dev_coredumpm - create device coredump with read/free methods |
309 | * @dev: the struct device for the crashed device |
310 | * @owner: the module that contains the read/free functions, use %THIS_MODULE |
311 | * @data: data cookie for the @read/@free functions |
312 | * @datalen: length of the data |
313 | * @gfp: allocation flags |
314 | * @read: function to read from the given buffer |
315 | * @free: function to free the given buffer |
316 | * |
317 | * Creates a new device coredump for the given device. If a previous one hasn't |
318 | * been read yet, the new coredump is discarded. The data lifetime is determined |
319 | * by the device coredump framework and when it is no longer needed the @free |
320 | * function will be called to free the data. |
321 | */ |
322 | void dev_coredumpm(struct device *dev, struct module *owner, |
323 | void *data, size_t datalen, gfp_t gfp, |
324 | ssize_t (*read)(char *buffer, loff_t offset, size_t count, |
325 | void *data, size_t datalen), |
326 | void (*free)(void *data)) |
327 | { |
328 | static atomic_t devcd_count = ATOMIC_INIT(0); |
329 | struct devcd_entry *devcd; |
330 | struct device *existing; |
331 | |
332 | if (devcd_disabled) |
333 | goto free; |
334 | |
335 | existing = class_find_device(class: &devcd_class, NULL, data: dev, |
336 | match: devcd_match_failing); |
337 | if (existing) { |
338 | put_device(dev: existing); |
339 | goto free; |
340 | } |
341 | |
342 | if (!try_module_get(module: owner)) |
343 | goto free; |
344 | |
345 | devcd = kzalloc(size: sizeof(*devcd), flags: gfp); |
346 | if (!devcd) |
347 | goto put_module; |
348 | |
349 | devcd->owner = owner; |
350 | devcd->data = data; |
351 | devcd->datalen = datalen; |
352 | devcd->read = read; |
353 | devcd->free = free; |
354 | devcd->failing_dev = get_device(dev); |
355 | devcd->delete_work = false; |
356 | |
357 | mutex_init(&devcd->mutex); |
358 | device_initialize(dev: &devcd->devcd_dev); |
359 | |
360 | dev_set_name(dev: &devcd->devcd_dev, name: "devcd%d" , |
361 | atomic_inc_return(v: &devcd_count)); |
362 | devcd->devcd_dev.class = &devcd_class; |
363 | |
364 | mutex_lock(&devcd->mutex); |
365 | if (device_add(dev: &devcd->devcd_dev)) |
366 | goto put_device; |
367 | |
368 | /* |
369 | * These should normally not fail, but there is no problem |
370 | * continuing without the links, so just warn instead of |
371 | * failing. |
372 | */ |
373 | if (sysfs_create_link(kobj: &devcd->devcd_dev.kobj, target: &dev->kobj, |
374 | name: "failing_device" ) || |
375 | sysfs_create_link(kobj: &dev->kobj, target: &devcd->devcd_dev.kobj, |
376 | name: "devcoredump" )) |
377 | dev_warn(dev, "devcoredump create_link failed\n" ); |
378 | |
379 | INIT_DELAYED_WORK(&devcd->del_wk, devcd_del); |
380 | schedule_delayed_work(dwork: &devcd->del_wk, DEVCD_TIMEOUT); |
381 | mutex_unlock(lock: &devcd->mutex); |
382 | return; |
383 | put_device: |
384 | put_device(dev: &devcd->devcd_dev); |
385 | mutex_unlock(lock: &devcd->mutex); |
386 | put_module: |
387 | module_put(module: owner); |
388 | free: |
389 | free(data); |
390 | } |
391 | EXPORT_SYMBOL_GPL(dev_coredumpm); |
392 | |
393 | /** |
394 | * dev_coredumpsg - create device coredump that uses scatterlist as data |
395 | * parameter |
396 | * @dev: the struct device for the crashed device |
397 | * @table: the dump data |
398 | * @datalen: length of the data |
399 | * @gfp: allocation flags |
400 | * |
401 | * Creates a new device coredump for the given device. If a previous one hasn't |
402 | * been read yet, the new coredump is discarded. The data lifetime is determined |
403 | * by the device coredump framework and when it is no longer needed |
404 | * it will free the data. |
405 | */ |
406 | void dev_coredumpsg(struct device *dev, struct scatterlist *table, |
407 | size_t datalen, gfp_t gfp) |
408 | { |
409 | dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable, |
410 | devcd_free_sgtable); |
411 | } |
412 | EXPORT_SYMBOL_GPL(dev_coredumpsg); |
413 | |
414 | static int __init devcoredump_init(void) |
415 | { |
416 | return class_register(class: &devcd_class); |
417 | } |
418 | __initcall(devcoredump_init); |
419 | |
420 | static void __exit devcoredump_exit(void) |
421 | { |
422 | class_for_each_device(class: &devcd_class, NULL, NULL, fn: devcd_free); |
423 | class_unregister(class: &devcd_class); |
424 | } |
425 | __exitcall(devcoredump_exit); |
426 | |