projects/linux·blob v2.6.21 · refs

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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
10#include <linux/capability.h>
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>
20#include <linux/signal.h>
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 */
31void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
32{
33 BUG_ON(!list_empty(&child->ptrace_list));
34 if (child->parent == new_parent)
35 return;
36 list_add(&child->ptrace_list, &child->parent->ptrace_children);
37 remove_parent(child);
38 child->parent = new_parent;
39 add_parent(child);
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 */
49void ptrace_untrace(struct task_struct *child)
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 */
68void __ptrace_unlink(struct task_struct *child)
69{
70 BUG_ON(!child->ptrace);
71
72 child->ptrace = 0;
73 if (!list_empty(&child->ptrace_list)) {
74 list_del_init(&child->ptrace_list);
75 remove_parent(child);
76 child->parent = child->real_parent;
77 add_parent(child);
78 }
79
80 if (child->state == TASK_TRACED)
81 ptrace_untrace(child);
82}
83
84/*
85 * Check that we have indeed attached to the thing..
86 */
87int 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
121static int may_attach(struct task_struct *task)
122{
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;
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();
143 if (task->mm)
144 dumpable = task->mm->dumpable;
145 if (!dumpable && !capable(CAP_SYS_PTRACE))
146 return -EPERM;
147
148 return security_ptrace(current, task);
149}
150
151int 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
160int ptrace_attach(struct task_struct *task)
161{
162 int retval;
163
164 retval = -EPERM;
165 if (task->pid <= 1)
166 goto out;
167 if (task->tgid == current->tgid)
168 goto out;
169
170repeat:
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 */
180 task_lock(task);
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 }
190
191 if (!task->mm)
192 goto bad;
193 /* the same process cannot be attached many times */
194 if (task->ptrace & PT_PTRACED)
195 goto bad;
196 retval = may_attach(task);
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;
205
206 __ptrace_link(task, current);
207
208 force_sig_specific(SIGSTOP, task);
209
210bad:
211 write_unlock_irq(&tasklist_lock);
212 task_unlock(task);
213out:
214 return retval;
215}
216
217static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
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
227int ptrace_detach(struct task_struct *child, unsigned int data)
228{
229 if (!valid_signal(data))
230 return -EIO;
231
232 /* Architecture-specific hardware disable .. */
233 ptrace_disable(child);
234
235 write_lock_irq(&tasklist_lock);
236 /* protect against de_thread()->release_task() */
237 if (child->ptrace)
238 __ptrace_detach(child, data);
239 write_unlock_irq(&tasklist_lock);
240
241 return 0;
242}
243
244int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
245{
246 int copied = 0;
247
248 while (len > 0) {
249 char buf[128];
250 int this_len, retval;
251
252 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
253 retval = access_process_vm(tsk, src, buf, this_len, 0);
254 if (!retval) {
255 if (copied)
256 break;
257 return -EIO;
258 }
259 if (copy_to_user(dst, buf, retval))
260 return -EFAULT;
261 copied += retval;
262 src += retval;
263 dst += retval;
264 len -= retval;
265 }
266 return copied;
267}
268
269int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
270{
271 int copied = 0;
272
273 while (len > 0) {
274 char buf[128];
275 int this_len, retval;
276
277 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
278 if (copy_from_user(buf, src, this_len))
279 return -EFAULT;
280 retval = access_process_vm(tsk, dst, buf, this_len, 1);
281 if (!retval) {
282 if (copied)
283 break;
284 return -EIO;
285 }
286 copied += retval;
287 src += retval;
288 dst += retval;
289 len -= retval;
290 }
291 return copied;
292}
293
294static int ptrace_setoptions(struct task_struct *child, long data)
295{
296 child->ptrace &= ~PT_TRACE_MASK;
297
298 if (data & PTRACE_O_TRACESYSGOOD)
299 child->ptrace |= PT_TRACESYSGOOD;
300
301 if (data & PTRACE_O_TRACEFORK)
302 child->ptrace |= PT_TRACE_FORK;
303
304 if (data & PTRACE_O_TRACEVFORK)
305 child->ptrace |= PT_TRACE_VFORK;
306
307 if (data & PTRACE_O_TRACECLONE)
308 child->ptrace |= PT_TRACE_CLONE;
309
310 if (data & PTRACE_O_TRACEEXEC)
311 child->ptrace |= PT_TRACE_EXEC;
312
313 if (data & PTRACE_O_TRACEVFORKDONE)
314 child->ptrace |= PT_TRACE_VFORK_DONE;
315
316 if (data & PTRACE_O_TRACEEXIT)
317 child->ptrace |= PT_TRACE_EXIT;
318
319 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
320}
321
322static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
323{
324 siginfo_t lastinfo;
325 int error = -ESRCH;
326
327 read_lock(&tasklist_lock);
328 if (likely(child->sighand != NULL)) {
329 error = -EINVAL;
330 spin_lock_irq(&child->sighand->siglock);
331 if (likely(child->last_siginfo != NULL)) {
332 lastinfo = *child->last_siginfo;
333 error = 0;
334 }
335 spin_unlock_irq(&child->sighand->siglock);
336 }
337 read_unlock(&tasklist_lock);
338 if (!error)
339 return copy_siginfo_to_user(data, &lastinfo);
340 return error;
341}
342
343static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
344{
345 siginfo_t newinfo;
346 int error = -ESRCH;
347
348 if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
349 return -EFAULT;
350
351 read_lock(&tasklist_lock);
352 if (likely(child->sighand != NULL)) {
353 error = -EINVAL;
354 spin_lock_irq(&child->sighand->siglock);
355 if (likely(child->last_siginfo != NULL)) {
356 *child->last_siginfo = newinfo;
357 error = 0;
358 }
359 spin_unlock_irq(&child->sighand->siglock);
360 }
361 read_unlock(&tasklist_lock);
362 return error;
363}
364
365int ptrace_request(struct task_struct *child, long request,
366 long addr, long data)
367{
368 int ret = -EIO;
369
370 switch (request) {
371#ifdef PTRACE_OLDSETOPTIONS
372 case PTRACE_OLDSETOPTIONS:
373#endif
374 case PTRACE_SETOPTIONS:
375 ret = ptrace_setoptions(child, data);
376 break;
377 case PTRACE_GETEVENTMSG:
378 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
379 break;
380 case PTRACE_GETSIGINFO:
381 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
382 break;
383 case PTRACE_SETSIGINFO:
384 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
385 break;
386 default:
387 break;
388 }
389
390 return ret;
391}
392
393/**
394 * ptrace_traceme -- helper for PTRACE_TRACEME
395 *
396 * Performs checks and sets PT_PTRACED.
397 * Should be used by all ptrace implementations for PTRACE_TRACEME.
398 */
399int ptrace_traceme(void)
400{
401 int ret = -EPERM;
402
403 /*
404 * Are we already being traced?
405 */
406 task_lock(current);
407 if (!(current->ptrace & PT_PTRACED)) {
408 ret = security_ptrace(current->parent, current);
409 /*
410 * Set the ptrace bit in the process ptrace flags.
411 */
412 if (!ret)
413 current->ptrace |= PT_PTRACED;
414 }
415 task_unlock(current);
416 return ret;
417}
418
419/**
420 * ptrace_get_task_struct -- grab a task struct reference for ptrace
421 * @pid: process id to grab a task_struct reference of
422 *
423 * This function is a helper for ptrace implementations. It checks
424 * permissions and then grabs a task struct for use of the actual
425 * ptrace implementation.
426 *
427 * Returns the task_struct for @pid or an ERR_PTR() on failure.
428 */
429struct task_struct *ptrace_get_task_struct(pid_t pid)
430{
431 struct task_struct *child;
432
433 /*
434 * Tracing init is not allowed.
435 */
436 if (pid == 1)
437 return ERR_PTR(-EPERM);
438
439 read_lock(&tasklist_lock);
440 child = find_task_by_pid(pid);
441 if (child)
442 get_task_struct(child);
443
444 read_unlock(&tasklist_lock);
445 if (!child)
446 return ERR_PTR(-ESRCH);
447 return child;
448}
449
450#ifndef __ARCH_SYS_PTRACE
451asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
452{
453 struct task_struct *child;
454 long ret;
455
456 /*
457 * This lock_kernel fixes a subtle race with suid exec
458 */
459 lock_kernel();
460 if (request == PTRACE_TRACEME) {
461 ret = ptrace_traceme();
462 goto out;
463 }
464
465 child = ptrace_get_task_struct(pid);
466 if (IS_ERR(child)) {
467 ret = PTR_ERR(child);
468 goto out;
469 }
470
471 if (request == PTRACE_ATTACH) {
472 ret = ptrace_attach(child);
473 goto out_put_task_struct;
474 }
475
476 ret = ptrace_check_attach(child, request == PTRACE_KILL);
477 if (ret < 0)
478 goto out_put_task_struct;
479
480 ret = arch_ptrace(child, request, addr, data);
481 if (ret < 0)
482 goto out_put_task_struct;
483
484 out_put_task_struct:
485 put_task_struct(child);
486 out:
487 unlock_kernel();
488 return ret;
489}
490#endif /* __ARCH_SYS_PTRACE */