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15#include <linux/security.h>
16#include <linux/sysctl.h>
17#include <linux/ptrace.h>
18#include <linux/prctl.h>
19#include <linux/ratelimit.h>
20#include <linux/workqueue.h>
21
22#define YAMA_SCOPE_DISABLED 0
23#define YAMA_SCOPE_RELATIONAL 1
24#define YAMA_SCOPE_CAPABILITY 2
25#define YAMA_SCOPE_NO_ATTACH 3
26
27static int ptrace_scope = YAMA_SCOPE_RELATIONAL;
28
29
30struct ptrace_relation {
31 struct task_struct *tracer;
32 struct task_struct *tracee;
33 bool invalid;
34 struct list_head node;
35 struct rcu_head rcu;
36};
37
38static LIST_HEAD(ptracer_relations);
39static DEFINE_SPINLOCK(ptracer_relations_lock);
40
41static void yama_relation_cleanup(struct work_struct *work);
42static DECLARE_WORK(yama_relation_work, yama_relation_cleanup);
43
44
45
46
47
48static void yama_relation_cleanup(struct work_struct *work)
49{
50 struct ptrace_relation *relation;
51
52 spin_lock(&ptracer_relations_lock);
53 rcu_read_lock();
54 list_for_each_entry_rcu(relation, &ptracer_relations, node) {
55 if (relation->invalid) {
56 list_del_rcu(&relation->node);
57 kfree_rcu(relation, rcu);
58 }
59 }
60 rcu_read_unlock();
61 spin_unlock(&ptracer_relations_lock);
62}
63
64
65
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70
71
72
73
74static int yama_ptracer_add(struct task_struct *tracer,
75 struct task_struct *tracee)
76{
77 struct ptrace_relation *relation, *added;
78
79 added = kmalloc(sizeof(*added), GFP_KERNEL);
80 if (!added)
81 return -ENOMEM;
82
83 added->tracee = tracee;
84 added->tracer = tracer;
85 added->invalid = false;
86
87 spin_lock(&ptracer_relations_lock);
88 rcu_read_lock();
89 list_for_each_entry_rcu(relation, &ptracer_relations, node) {
90 if (relation->invalid)
91 continue;
92 if (relation->tracee == tracee) {
93 list_replace_rcu(&relation->node, &added->node);
94 kfree_rcu(relation, rcu);
95 goto out;
96 }
97 }
98
99 list_add_rcu(&added->node, &ptracer_relations);
100
101out:
102 rcu_read_unlock();
103 spin_unlock(&ptracer_relations_lock);
104 return 0;
105}
106
107
108
109
110
111
112static void yama_ptracer_del(struct task_struct *tracer,
113 struct task_struct *tracee)
114{
115 struct ptrace_relation *relation;
116 bool marked = false;
117
118 rcu_read_lock();
119 list_for_each_entry_rcu(relation, &ptracer_relations, node) {
120 if (relation->invalid)
121 continue;
122 if (relation->tracee == tracee ||
123 (tracer && relation->tracer == tracer)) {
124 relation->invalid = true;
125 marked = true;
126 }
127 }
128 rcu_read_unlock();
129
130 if (marked)
131 schedule_work(&yama_relation_work);
132}
133
134
135
136
137
138void yama_task_free(struct task_struct *task)
139{
140 yama_ptracer_del(task, task);
141}
142
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152
153
154int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
155 unsigned long arg4, unsigned long arg5)
156{
157 int rc;
158 struct task_struct *myself = current;
159
160 rc = cap_task_prctl(option, arg2, arg3, arg4, arg5);
161 if (rc != -ENOSYS)
162 return rc;
163
164 switch (option) {
165 case PR_SET_PTRACER:
166
167
168
169
170
171
172 rcu_read_lock();
173 if (!thread_group_leader(myself))
174 myself = rcu_dereference(myself->group_leader);
175 get_task_struct(myself);
176 rcu_read_unlock();
177
178 if (arg2 == 0) {
179 yama_ptracer_del(NULL, myself);
180 rc = 0;
181 } else if (arg2 == PR_SET_PTRACER_ANY || (int)arg2 == -1) {
182 rc = yama_ptracer_add(NULL, myself);
183 } else {
184 struct task_struct *tracer;
185
186 rcu_read_lock();
187 tracer = find_task_by_vpid(arg2);
188 if (tracer)
189 get_task_struct(tracer);
190 else
191 rc = -EINVAL;
192 rcu_read_unlock();
193
194 if (tracer) {
195 rc = yama_ptracer_add(tracer, myself);
196 put_task_struct(tracer);
197 }
198 }
199
200 put_task_struct(myself);
201 break;
202 }
203
204 return rc;
205}
206
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211
212
213
214static int task_is_descendant(struct task_struct *parent,
215 struct task_struct *child)
216{
217 int rc = 0;
218 struct task_struct *walker = child;
219
220 if (!parent || !child)
221 return 0;
222
223 rcu_read_lock();
224 if (!thread_group_leader(parent))
225 parent = rcu_dereference(parent->group_leader);
226 while (walker->pid > 0) {
227 if (!thread_group_leader(walker))
228 walker = rcu_dereference(walker->group_leader);
229 if (walker == parent) {
230 rc = 1;
231 break;
232 }
233 walker = rcu_dereference(walker->real_parent);
234 }
235 rcu_read_unlock();
236
237 return rc;
238}
239
240
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244
245
246
247static int ptracer_exception_found(struct task_struct *tracer,
248 struct task_struct *tracee)
249{
250 int rc = 0;
251 struct ptrace_relation *relation;
252 struct task_struct *parent = NULL;
253 bool found = false;
254
255 rcu_read_lock();
256 if (!thread_group_leader(tracee))
257 tracee = rcu_dereference(tracee->group_leader);
258 list_for_each_entry_rcu(relation, &ptracer_relations, node) {
259 if (relation->invalid)
260 continue;
261 if (relation->tracee == tracee) {
262 parent = relation->tracer;
263 found = true;
264 break;
265 }
266 }
267
268 if (found && (parent == NULL || task_is_descendant(parent, tracer)))
269 rc = 1;
270 rcu_read_unlock();
271
272 return rc;
273}
274
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280
281
282int yama_ptrace_access_check(struct task_struct *child,
283 unsigned int mode)
284{
285 int rc;
286
287
288
289
290 rc = cap_ptrace_access_check(child, mode);
291 if (rc)
292 return rc;
293
294
295 if (mode == PTRACE_MODE_ATTACH) {
296 switch (ptrace_scope) {
297 case YAMA_SCOPE_DISABLED:
298
299 break;
300 case YAMA_SCOPE_RELATIONAL:
301 rcu_read_lock();
302 if (!task_is_descendant(current, child) &&
303 !ptracer_exception_found(current, child) &&
304 !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
305 rc = -EPERM;
306 rcu_read_unlock();
307 break;
308 case YAMA_SCOPE_CAPABILITY:
309 rcu_read_lock();
310 if (!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
311 rc = -EPERM;
312 rcu_read_unlock();
313 break;
314 case YAMA_SCOPE_NO_ATTACH:
315 default:
316 rc = -EPERM;
317 break;
318 }
319 }
320
321 if (rc) {
322 printk_ratelimited(KERN_NOTICE
323 "ptrace of pid %d was attempted by: %s (pid %d)\n",
324 child->pid, current->comm, current->pid);
325 }
326
327 return rc;
328}
329
330
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333
334
335
336int yama_ptrace_traceme(struct task_struct *parent)
337{
338 int rc;
339
340
341
342
343 rc = cap_ptrace_traceme(parent);
344 if (rc)
345 return rc;
346
347
348 switch (ptrace_scope) {
349 case YAMA_SCOPE_CAPABILITY:
350 if (!has_ns_capability(parent, current_user_ns(), CAP_SYS_PTRACE))
351 rc = -EPERM;
352 break;
353 case YAMA_SCOPE_NO_ATTACH:
354 rc = -EPERM;
355 break;
356 }
357
358 if (rc) {
359 printk_ratelimited(KERN_NOTICE
360 "ptraceme of pid %d was attempted by: %s (pid %d)\n",
361 current->pid, parent->comm, parent->pid);
362 }
363
364 return rc;
365}
366
367#ifndef CONFIG_SECURITY_YAMA_STACKED
368static struct security_operations yama_ops = {
369 .name = "yama",
370
371 .ptrace_access_check = yama_ptrace_access_check,
372 .ptrace_traceme = yama_ptrace_traceme,
373 .task_prctl = yama_task_prctl,
374 .task_free = yama_task_free,
375};
376#endif
377
378#ifdef CONFIG_SYSCTL
379static int yama_dointvec_minmax(struct ctl_table *table, int write,
380 void __user *buffer, size_t *lenp, loff_t *ppos)
381{
382 int rc;
383
384 if (write && !capable(CAP_SYS_PTRACE))
385 return -EPERM;
386
387 rc = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
388 if (rc)
389 return rc;
390
391
392 if (write && *(int *)table->data == *(int *)table->extra2)
393 table->extra1 = table->extra2;
394
395 return rc;
396}
397
398static int zero;
399static int max_scope = YAMA_SCOPE_NO_ATTACH;
400
401struct ctl_path yama_sysctl_path[] = {
402 { .procname = "kernel", },
403 { .procname = "yama", },
404 { }
405};
406
407static struct ctl_table yama_sysctl_table[] = {
408 {
409 .procname = "ptrace_scope",
410 .data = &ptrace_scope,
411 .maxlen = sizeof(int),
412 .mode = 0644,
413 .proc_handler = yama_dointvec_minmax,
414 .extra1 = &zero,
415 .extra2 = &max_scope,
416 },
417 { }
418};
419#endif
420
421static __init int yama_init(void)
422{
423#ifndef CONFIG_SECURITY_YAMA_STACKED
424 if (!security_module_enable(&yama_ops))
425 return 0;
426#endif
427
428 printk(KERN_INFO "Yama: becoming mindful.\n");
429
430#ifndef CONFIG_SECURITY_YAMA_STACKED
431 if (register_security(&yama_ops))
432 panic("Yama: kernel registration failed.\n");
433#endif
434
435#ifdef CONFIG_SYSCTL
436 if (!register_sysctl_paths(yama_sysctl_path, yama_sysctl_table))
437 panic("Yama: sysctl registration failed.\n");
438#endif
439
440 return 0;
441}
442
443security_initcall(yama_init);
444