Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * linux/kernel/ptrace.c | |
3 | * | |
4 | * (C) Copyright 1999 Linus Torvalds | |
5 | * | |
6 | * Common interfaces for "ptrace()" which we do not want | |
7 | * to continually duplicate across every architecture. | |
8 | */ | |
9 | ||
c59ede7b | 10 | #include <linux/capability.h> |
1da177e4 LT |
11 | #include <linux/module.h> |
12 | #include <linux/sched.h> | |
13 | #include <linux/errno.h> | |
14 | #include <linux/mm.h> | |
15 | #include <linux/highmem.h> | |
16 | #include <linux/pagemap.h> | |
17 | #include <linux/smp_lock.h> | |
18 | #include <linux/ptrace.h> | |
19 | #include <linux/security.h> | |
7ed20e1a | 20 | #include <linux/signal.h> |
1da177e4 LT |
21 | |
22 | #include <asm/pgtable.h> | |
23 | #include <asm/uaccess.h> | |
24 | ||
25 | /* | |
26 | * ptrace a task: make the debugger its new parent and | |
27 | * move it to the ptrace list. | |
28 | * | |
29 | * Must be called with the tasklist lock write-held. | |
30 | */ | |
36c8b586 | 31 | void __ptrace_link(struct task_struct *child, struct task_struct *new_parent) |
1da177e4 | 32 | { |
524223ca | 33 | BUG_ON(!list_empty(&child->ptrace_list)); |
1da177e4 LT |
34 | if (child->parent == new_parent) |
35 | return; | |
36 | list_add(&child->ptrace_list, &child->parent->ptrace_children); | |
9b678ece | 37 | remove_parent(child); |
1da177e4 | 38 | child->parent = new_parent; |
9b678ece | 39 | add_parent(child); |
1da177e4 LT |
40 | } |
41 | ||
42 | /* | |
43 | * Turn a tracing stop into a normal stop now, since with no tracer there | |
44 | * would be no way to wake it up with SIGCONT or SIGKILL. If there was a | |
45 | * signal sent that would resume the child, but didn't because it was in | |
46 | * TASK_TRACED, resume it now. | |
47 | * Requires that irqs be disabled. | |
48 | */ | |
36c8b586 | 49 | void ptrace_untrace(struct task_struct *child) |
1da177e4 LT |
50 | { |
51 | spin_lock(&child->sighand->siglock); | |
52 | if (child->state == TASK_TRACED) { | |
53 | if (child->signal->flags & SIGNAL_STOP_STOPPED) { | |
54 | child->state = TASK_STOPPED; | |
55 | } else { | |
56 | signal_wake_up(child, 1); | |
57 | } | |
58 | } | |
59 | spin_unlock(&child->sighand->siglock); | |
60 | } | |
61 | ||
62 | /* | |
63 | * unptrace a task: move it back to its original parent and | |
64 | * remove it from the ptrace list. | |
65 | * | |
66 | * Must be called with the tasklist lock write-held. | |
67 | */ | |
36c8b586 | 68 | void __ptrace_unlink(struct task_struct *child) |
1da177e4 | 69 | { |
5ecfbae0 ON |
70 | BUG_ON(!child->ptrace); |
71 | ||
1da177e4 LT |
72 | child->ptrace = 0; |
73 | if (!list_empty(&child->ptrace_list)) { | |
74 | list_del_init(&child->ptrace_list); | |
9b678ece | 75 | remove_parent(child); |
1da177e4 | 76 | child->parent = child->real_parent; |
9b678ece | 77 | add_parent(child); |
1da177e4 LT |
78 | } |
79 | ||
e57a5059 RM |
80 | if (child->state == TASK_TRACED) |
81 | ptrace_untrace(child); | |
1da177e4 LT |
82 | } |
83 | ||
84 | /* | |
85 | * Check that we have indeed attached to the thing.. | |
86 | */ | |
87 | int ptrace_check_attach(struct task_struct *child, int kill) | |
88 | { | |
89 | int ret = -ESRCH; | |
90 | ||
91 | /* | |
92 | * We take the read lock around doing both checks to close a | |
93 | * possible race where someone else was tracing our child and | |
94 | * detached between these two checks. After this locked check, | |
95 | * we are sure that this is our traced child and that can only | |
96 | * be changed by us so it's not changing right after this. | |
97 | */ | |
98 | read_lock(&tasklist_lock); | |
99 | if ((child->ptrace & PT_PTRACED) && child->parent == current && | |
100 | (!(child->ptrace & PT_ATTACHED) || child->real_parent != current) | |
101 | && child->signal != NULL) { | |
102 | ret = 0; | |
103 | spin_lock_irq(&child->sighand->siglock); | |
104 | if (child->state == TASK_STOPPED) { | |
105 | child->state = TASK_TRACED; | |
106 | } else if (child->state != TASK_TRACED && !kill) { | |
107 | ret = -ESRCH; | |
108 | } | |
109 | spin_unlock_irq(&child->sighand->siglock); | |
110 | } | |
111 | read_unlock(&tasklist_lock); | |
112 | ||
113 | if (!ret && !kill) { | |
114 | wait_task_inactive(child); | |
115 | } | |
116 | ||
117 | /* All systems go.. */ | |
118 | return ret; | |
119 | } | |
120 | ||
ab8d11be MS |
121 | static int may_attach(struct task_struct *task) |
122 | { | |
df26c40e EB |
123 | /* May we inspect the given task? |
124 | * This check is used both for attaching with ptrace | |
125 | * and for allowing access to sensitive information in /proc. | |
126 | * | |
127 | * ptrace_attach denies several cases that /proc allows | |
128 | * because setting up the necessary parent/child relationship | |
129 | * or halting the specified task is impossible. | |
130 | */ | |
131 | int dumpable = 0; | |
132 | /* Don't let security modules deny introspection */ | |
133 | if (task == current) | |
134 | return 0; | |
ab8d11be MS |
135 | if (((current->uid != task->euid) || |
136 | (current->uid != task->suid) || | |
137 | (current->uid != task->uid) || | |
138 | (current->gid != task->egid) || | |
139 | (current->gid != task->sgid) || | |
140 | (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE)) | |
141 | return -EPERM; | |
142 | smp_rmb(); | |
df26c40e EB |
143 | if (task->mm) |
144 | dumpable = task->mm->dumpable; | |
145 | if (!dumpable && !capable(CAP_SYS_PTRACE)) | |
ab8d11be MS |
146 | return -EPERM; |
147 | ||
148 | return security_ptrace(current, task); | |
149 | } | |
150 | ||
151 | int ptrace_may_attach(struct task_struct *task) | |
152 | { | |
153 | int err; | |
154 | task_lock(task); | |
155 | err = may_attach(task); | |
156 | task_unlock(task); | |
157 | return !err; | |
158 | } | |
159 | ||
1da177e4 LT |
160 | int ptrace_attach(struct task_struct *task) |
161 | { | |
162 | int retval; | |
f5b40e36 | 163 | |
1da177e4 LT |
164 | retval = -EPERM; |
165 | if (task->pid <= 1) | |
f5b40e36 | 166 | goto out; |
28d838cc | 167 | if (task->tgid == current->tgid) |
f5b40e36 LT |
168 | goto out; |
169 | ||
f358166a LT |
170 | repeat: |
171 | /* | |
172 | * Nasty, nasty. | |
173 | * | |
174 | * We want to hold both the task-lock and the | |
175 | * tasklist_lock for writing at the same time. | |
176 | * But that's against the rules (tasklist_lock | |
177 | * is taken for reading by interrupts on other | |
178 | * cpu's that may have task_lock). | |
179 | */ | |
f5b40e36 | 180 | task_lock(task); |
f358166a LT |
181 | local_irq_disable(); |
182 | if (!write_trylock(&tasklist_lock)) { | |
183 | local_irq_enable(); | |
184 | task_unlock(task); | |
185 | do { | |
186 | cpu_relax(); | |
187 | } while (!write_can_lock(&tasklist_lock)); | |
188 | goto repeat; | |
189 | } | |
f5b40e36 | 190 | |
df26c40e EB |
191 | if (!task->mm) |
192 | goto bad; | |
1da177e4 LT |
193 | /* the same process cannot be attached many times */ |
194 | if (task->ptrace & PT_PTRACED) | |
195 | goto bad; | |
ab8d11be | 196 | retval = may_attach(task); |
1da177e4 LT |
197 | if (retval) |
198 | goto bad; | |
199 | ||
200 | /* Go */ | |
201 | task->ptrace |= PT_PTRACED | ((task->real_parent != current) | |
202 | ? PT_ATTACHED : 0); | |
203 | if (capable(CAP_SYS_PTRACE)) | |
204 | task->ptrace |= PT_PTRACE_CAP; | |
1da177e4 | 205 | |
1da177e4 | 206 | __ptrace_link(task, current); |
1da177e4 LT |
207 | |
208 | force_sig_specific(SIGSTOP, task); | |
1da177e4 LT |
209 | |
210 | bad: | |
f5b40e36 | 211 | write_unlock_irq(&tasklist_lock); |
1da177e4 | 212 | task_unlock(task); |
f5b40e36 | 213 | out: |
1da177e4 LT |
214 | return retval; |
215 | } | |
216 | ||
d5f70c00 | 217 | static inline void __ptrace_detach(struct task_struct *child, unsigned int data) |
5ecfbae0 ON |
218 | { |
219 | child->exit_code = data; | |
220 | /* .. re-parent .. */ | |
221 | __ptrace_unlink(child); | |
222 | /* .. and wake it up. */ | |
223 | if (child->exit_state != EXIT_ZOMBIE) | |
224 | wake_up_process(child); | |
225 | } | |
226 | ||
1da177e4 LT |
227 | int ptrace_detach(struct task_struct *child, unsigned int data) |
228 | { | |
7ed20e1a | 229 | if (!valid_signal(data)) |
5ecfbae0 | 230 | return -EIO; |
1da177e4 LT |
231 | |
232 | /* Architecture-specific hardware disable .. */ | |
233 | ptrace_disable(child); | |
234 | ||
1da177e4 | 235 | write_lock_irq(&tasklist_lock); |
d5f70c00 | 236 | /* protect against de_thread()->release_task() */ |
5ecfbae0 ON |
237 | if (child->ptrace) |
238 | __ptrace_detach(child, data); | |
1da177e4 LT |
239 | write_unlock_irq(&tasklist_lock); |
240 | ||
241 | return 0; | |
242 | } | |
243 | ||
244 | /* | |
245 | * Access another process' address space. | |
246 | * Source/target buffer must be kernel space, | |
247 | * Do not walk the page table directly, use get_user_pages | |
248 | */ | |
249 | ||
250 | int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write) | |
251 | { | |
252 | struct mm_struct *mm; | |
253 | struct vm_area_struct *vma; | |
254 | struct page *page; | |
255 | void *old_buf = buf; | |
256 | ||
257 | mm = get_task_mm(tsk); | |
258 | if (!mm) | |
259 | return 0; | |
260 | ||
261 | down_read(&mm->mmap_sem); | |
262 | /* ignore errors, just check how much was sucessfully transfered */ | |
263 | while (len) { | |
264 | int bytes, ret, offset; | |
265 | void *maddr; | |
266 | ||
267 | ret = get_user_pages(tsk, mm, addr, 1, | |
268 | write, 1, &page, &vma); | |
269 | if (ret <= 0) | |
270 | break; | |
271 | ||
272 | bytes = len; | |
273 | offset = addr & (PAGE_SIZE-1); | |
274 | if (bytes > PAGE_SIZE-offset) | |
275 | bytes = PAGE_SIZE-offset; | |
276 | ||
277 | maddr = kmap(page); | |
278 | if (write) { | |
279 | copy_to_user_page(vma, page, addr, | |
280 | maddr + offset, buf, bytes); | |
16bf1348 | 281 | set_page_dirty_lock(page); |
1da177e4 LT |
282 | } else { |
283 | copy_from_user_page(vma, page, addr, | |
284 | buf, maddr + offset, bytes); | |
285 | } | |
286 | kunmap(page); | |
287 | page_cache_release(page); | |
288 | len -= bytes; | |
289 | buf += bytes; | |
290 | addr += bytes; | |
291 | } | |
292 | up_read(&mm->mmap_sem); | |
293 | mmput(mm); | |
294 | ||
295 | return buf - old_buf; | |
296 | } | |
297 | ||
298 | int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len) | |
299 | { | |
300 | int copied = 0; | |
301 | ||
302 | while (len > 0) { | |
303 | char buf[128]; | |
304 | int this_len, retval; | |
305 | ||
306 | this_len = (len > sizeof(buf)) ? sizeof(buf) : len; | |
307 | retval = access_process_vm(tsk, src, buf, this_len, 0); | |
308 | if (!retval) { | |
309 | if (copied) | |
310 | break; | |
311 | return -EIO; | |
312 | } | |
313 | if (copy_to_user(dst, buf, retval)) | |
314 | return -EFAULT; | |
315 | copied += retval; | |
316 | src += retval; | |
317 | dst += retval; | |
318 | len -= retval; | |
319 | } | |
320 | return copied; | |
321 | } | |
322 | ||
323 | int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len) | |
324 | { | |
325 | int copied = 0; | |
326 | ||
327 | while (len > 0) { | |
328 | char buf[128]; | |
329 | int this_len, retval; | |
330 | ||
331 | this_len = (len > sizeof(buf)) ? sizeof(buf) : len; | |
332 | if (copy_from_user(buf, src, this_len)) | |
333 | return -EFAULT; | |
334 | retval = access_process_vm(tsk, dst, buf, this_len, 1); | |
335 | if (!retval) { | |
336 | if (copied) | |
337 | break; | |
338 | return -EIO; | |
339 | } | |
340 | copied += retval; | |
341 | src += retval; | |
342 | dst += retval; | |
343 | len -= retval; | |
344 | } | |
345 | return copied; | |
346 | } | |
347 | ||
348 | static int ptrace_setoptions(struct task_struct *child, long data) | |
349 | { | |
350 | child->ptrace &= ~PT_TRACE_MASK; | |
351 | ||
352 | if (data & PTRACE_O_TRACESYSGOOD) | |
353 | child->ptrace |= PT_TRACESYSGOOD; | |
354 | ||
355 | if (data & PTRACE_O_TRACEFORK) | |
356 | child->ptrace |= PT_TRACE_FORK; | |
357 | ||
358 | if (data & PTRACE_O_TRACEVFORK) | |
359 | child->ptrace |= PT_TRACE_VFORK; | |
360 | ||
361 | if (data & PTRACE_O_TRACECLONE) | |
362 | child->ptrace |= PT_TRACE_CLONE; | |
363 | ||
364 | if (data & PTRACE_O_TRACEEXEC) | |
365 | child->ptrace |= PT_TRACE_EXEC; | |
366 | ||
367 | if (data & PTRACE_O_TRACEVFORKDONE) | |
368 | child->ptrace |= PT_TRACE_VFORK_DONE; | |
369 | ||
370 | if (data & PTRACE_O_TRACEEXIT) | |
371 | child->ptrace |= PT_TRACE_EXIT; | |
372 | ||
373 | return (data & ~PTRACE_O_MASK) ? -EINVAL : 0; | |
374 | } | |
375 | ||
376 | static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data) | |
377 | { | |
378 | siginfo_t lastinfo; | |
379 | int error = -ESRCH; | |
380 | ||
381 | read_lock(&tasklist_lock); | |
382 | if (likely(child->sighand != NULL)) { | |
383 | error = -EINVAL; | |
384 | spin_lock_irq(&child->sighand->siglock); | |
385 | if (likely(child->last_siginfo != NULL)) { | |
386 | lastinfo = *child->last_siginfo; | |
387 | error = 0; | |
388 | } | |
389 | spin_unlock_irq(&child->sighand->siglock); | |
390 | } | |
391 | read_unlock(&tasklist_lock); | |
392 | if (!error) | |
393 | return copy_siginfo_to_user(data, &lastinfo); | |
394 | return error; | |
395 | } | |
396 | ||
397 | static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data) | |
398 | { | |
399 | siginfo_t newinfo; | |
400 | int error = -ESRCH; | |
401 | ||
402 | if (copy_from_user(&newinfo, data, sizeof (siginfo_t))) | |
403 | return -EFAULT; | |
404 | ||
405 | read_lock(&tasklist_lock); | |
406 | if (likely(child->sighand != NULL)) { | |
407 | error = -EINVAL; | |
408 | spin_lock_irq(&child->sighand->siglock); | |
409 | if (likely(child->last_siginfo != NULL)) { | |
410 | *child->last_siginfo = newinfo; | |
411 | error = 0; | |
412 | } | |
413 | spin_unlock_irq(&child->sighand->siglock); | |
414 | } | |
415 | read_unlock(&tasklist_lock); | |
416 | return error; | |
417 | } | |
418 | ||
419 | int ptrace_request(struct task_struct *child, long request, | |
420 | long addr, long data) | |
421 | { | |
422 | int ret = -EIO; | |
423 | ||
424 | switch (request) { | |
425 | #ifdef PTRACE_OLDSETOPTIONS | |
426 | case PTRACE_OLDSETOPTIONS: | |
427 | #endif | |
428 | case PTRACE_SETOPTIONS: | |
429 | ret = ptrace_setoptions(child, data); | |
430 | break; | |
431 | case PTRACE_GETEVENTMSG: | |
432 | ret = put_user(child->ptrace_message, (unsigned long __user *) data); | |
433 | break; | |
434 | case PTRACE_GETSIGINFO: | |
435 | ret = ptrace_getsiginfo(child, (siginfo_t __user *) data); | |
436 | break; | |
437 | case PTRACE_SETSIGINFO: | |
438 | ret = ptrace_setsiginfo(child, (siginfo_t __user *) data); | |
439 | break; | |
440 | default: | |
441 | break; | |
442 | } | |
443 | ||
444 | return ret; | |
445 | } | |
481bed45 | 446 | |
6b9c7ed8 CH |
447 | /** |
448 | * ptrace_traceme -- helper for PTRACE_TRACEME | |
449 | * | |
450 | * Performs checks and sets PT_PTRACED. | |
451 | * Should be used by all ptrace implementations for PTRACE_TRACEME. | |
452 | */ | |
453 | int ptrace_traceme(void) | |
481bed45 | 454 | { |
f5b40e36 | 455 | int ret = -EPERM; |
481bed45 CH |
456 | |
457 | /* | |
6b9c7ed8 CH |
458 | * Are we already being traced? |
459 | */ | |
f5b40e36 LT |
460 | task_lock(current); |
461 | if (!(current->ptrace & PT_PTRACED)) { | |
462 | ret = security_ptrace(current->parent, current); | |
463 | /* | |
464 | * Set the ptrace bit in the process ptrace flags. | |
465 | */ | |
466 | if (!ret) | |
467 | current->ptrace |= PT_PTRACED; | |
468 | } | |
469 | task_unlock(current); | |
470 | return ret; | |
6b9c7ed8 | 471 | } |
481bed45 | 472 | |
6b9c7ed8 CH |
473 | /** |
474 | * ptrace_get_task_struct -- grab a task struct reference for ptrace | |
475 | * @pid: process id to grab a task_struct reference of | |
476 | * | |
477 | * This function is a helper for ptrace implementations. It checks | |
478 | * permissions and then grabs a task struct for use of the actual | |
479 | * ptrace implementation. | |
480 | * | |
481 | * Returns the task_struct for @pid or an ERR_PTR() on failure. | |
482 | */ | |
483 | struct task_struct *ptrace_get_task_struct(pid_t pid) | |
484 | { | |
485 | struct task_struct *child; | |
481bed45 CH |
486 | |
487 | /* | |
6b9c7ed8 | 488 | * Tracing init is not allowed. |
481bed45 CH |
489 | */ |
490 | if (pid == 1) | |
6b9c7ed8 | 491 | return ERR_PTR(-EPERM); |
481bed45 | 492 | |
481bed45 CH |
493 | read_lock(&tasklist_lock); |
494 | child = find_task_by_pid(pid); | |
495 | if (child) | |
496 | get_task_struct(child); | |
497 | read_unlock(&tasklist_lock); | |
498 | if (!child) | |
6b9c7ed8 CH |
499 | return ERR_PTR(-ESRCH); |
500 | return child; | |
481bed45 CH |
501 | } |
502 | ||
6b9c7ed8 | 503 | #ifndef __ARCH_SYS_PTRACE |
481bed45 CH |
504 | asmlinkage long sys_ptrace(long request, long pid, long addr, long data) |
505 | { | |
506 | struct task_struct *child; | |
507 | long ret; | |
508 | ||
509 | /* | |
510 | * This lock_kernel fixes a subtle race with suid exec | |
511 | */ | |
512 | lock_kernel(); | |
6b9c7ed8 CH |
513 | if (request == PTRACE_TRACEME) { |
514 | ret = ptrace_traceme(); | |
481bed45 | 515 | goto out; |
6b9c7ed8 CH |
516 | } |
517 | ||
518 | child = ptrace_get_task_struct(pid); | |
519 | if (IS_ERR(child)) { | |
520 | ret = PTR_ERR(child); | |
521 | goto out; | |
522 | } | |
481bed45 CH |
523 | |
524 | if (request == PTRACE_ATTACH) { | |
525 | ret = ptrace_attach(child); | |
005f18df | 526 | goto out_put_task_struct; |
481bed45 CH |
527 | } |
528 | ||
529 | ret = ptrace_check_attach(child, request == PTRACE_KILL); | |
530 | if (ret < 0) | |
531 | goto out_put_task_struct; | |
532 | ||
533 | ret = arch_ptrace(child, request, addr, data); | |
534 | if (ret < 0) | |
535 | goto out_put_task_struct; | |
536 | ||
537 | out_put_task_struct: | |
538 | put_task_struct(child); | |
539 | out: | |
540 | unlock_kernel(); | |
541 | return ret; | |
542 | } | |
543 | #endif /* __ARCH_SYS_PTRACE */ |