CRED: Rename cred_exec_mutex to reflect that it's a guard against ptrace
[linux-2.6.git] / kernel / ptrace.c
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 #include <linux/audit.h>
22 #include <linux/pid_namespace.h>
23 #include <linux/syscalls.h>
24 #include <linux/uaccess.h>
25
26
27 /*
28  * Initialize a new task whose father had been ptraced.
29  *
30  * Called from copy_process().
31  */
32 void ptrace_fork(struct task_struct *child, unsigned long clone_flags)
33 {
34         arch_ptrace_fork(child, clone_flags);
35 }
36
37 /*
38  * ptrace a task: make the debugger its new parent and
39  * move it to the ptrace list.
40  *
41  * Must be called with the tasklist lock write-held.
42  */
43 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
44 {
45         BUG_ON(!list_empty(&child->ptrace_entry));
46         list_add(&child->ptrace_entry, &new_parent->ptraced);
47         child->parent = new_parent;
48 }
49
50 /*
51  * Turn a tracing stop into a normal stop now, since with no tracer there
52  * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
53  * signal sent that would resume the child, but didn't because it was in
54  * TASK_TRACED, resume it now.
55  * Requires that irqs be disabled.
56  */
57 static void ptrace_untrace(struct task_struct *child)
58 {
59         spin_lock(&child->sighand->siglock);
60         if (task_is_traced(child)) {
61                 /*
62                  * If the group stop is completed or in progress,
63                  * this thread was already counted as stopped.
64                  */
65                 if (child->signal->flags & SIGNAL_STOP_STOPPED ||
66                     child->signal->group_stop_count)
67                         __set_task_state(child, TASK_STOPPED);
68                 else
69                         signal_wake_up(child, 1);
70         }
71         spin_unlock(&child->sighand->siglock);
72 }
73
74 /*
75  * unptrace a task: move it back to its original parent and
76  * remove it from the ptrace list.
77  *
78  * Must be called with the tasklist lock write-held.
79  */
80 void __ptrace_unlink(struct task_struct *child)
81 {
82         BUG_ON(!child->ptrace);
83
84         child->ptrace = 0;
85         child->parent = child->real_parent;
86         list_del_init(&child->ptrace_entry);
87
88         arch_ptrace_untrace(child);
89         if (task_is_traced(child))
90                 ptrace_untrace(child);
91 }
92
93 /*
94  * Check that we have indeed attached to the thing..
95  */
96 int ptrace_check_attach(struct task_struct *child, int kill)
97 {
98         int ret = -ESRCH;
99
100         /*
101          * We take the read lock around doing both checks to close a
102          * possible race where someone else was tracing our child and
103          * detached between these two checks.  After this locked check,
104          * we are sure that this is our traced child and that can only
105          * be changed by us so it's not changing right after this.
106          */
107         read_lock(&tasklist_lock);
108         if ((child->ptrace & PT_PTRACED) && child->parent == current) {
109                 ret = 0;
110                 /*
111                  * child->sighand can't be NULL, release_task()
112                  * does ptrace_unlink() before __exit_signal().
113                  */
114                 spin_lock_irq(&child->sighand->siglock);
115                 if (task_is_stopped(child))
116                         child->state = TASK_TRACED;
117                 else if (!task_is_traced(child) && !kill)
118                         ret = -ESRCH;
119                 spin_unlock_irq(&child->sighand->siglock);
120         }
121         read_unlock(&tasklist_lock);
122
123         if (!ret && !kill)
124                 ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;
125
126         /* All systems go.. */
127         return ret;
128 }
129
130 int __ptrace_may_access(struct task_struct *task, unsigned int mode)
131 {
132         const struct cred *cred = current_cred(), *tcred;
133
134         /* May we inspect the given task?
135          * This check is used both for attaching with ptrace
136          * and for allowing access to sensitive information in /proc.
137          *
138          * ptrace_attach denies several cases that /proc allows
139          * because setting up the necessary parent/child relationship
140          * or halting the specified task is impossible.
141          */
142         int dumpable = 0;
143         /* Don't let security modules deny introspection */
144         if (task == current)
145                 return 0;
146         rcu_read_lock();
147         tcred = __task_cred(task);
148         if ((cred->uid != tcred->euid ||
149              cred->uid != tcred->suid ||
150              cred->uid != tcred->uid  ||
151              cred->gid != tcred->egid ||
152              cred->gid != tcred->sgid ||
153              cred->gid != tcred->gid) &&
154             !capable(CAP_SYS_PTRACE)) {
155                 rcu_read_unlock();
156                 return -EPERM;
157         }
158         rcu_read_unlock();
159         smp_rmb();
160         if (task->mm)
161                 dumpable = get_dumpable(task->mm);
162         if (!dumpable && !capable(CAP_SYS_PTRACE))
163                 return -EPERM;
164
165         return security_ptrace_may_access(task, mode);
166 }
167
168 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
169 {
170         int err;
171         task_lock(task);
172         err = __ptrace_may_access(task, mode);
173         task_unlock(task);
174         return !err;
175 }
176
177 int ptrace_attach(struct task_struct *task)
178 {
179         int retval;
180         unsigned long flags;
181
182         audit_ptrace(task);
183
184         retval = -EPERM;
185         if (same_thread_group(task, current))
186                 goto out;
187
188         /* Protect the target's credential calculations against our
189          * interference; SUID, SGID and LSM creds get determined differently
190          * under ptrace.
191          */
192         retval = mutex_lock_interruptible(&task->cred_guard_mutex);
193         if (retval  < 0)
194                 goto out;
195
196         retval = -EPERM;
197 repeat:
198         /*
199          * Nasty, nasty.
200          *
201          * We want to hold both the task-lock and the
202          * tasklist_lock for writing at the same time.
203          * But that's against the rules (tasklist_lock
204          * is taken for reading by interrupts on other
205          * cpu's that may have task_lock).
206          */
207         task_lock(task);
208         if (!write_trylock_irqsave(&tasklist_lock, flags)) {
209                 task_unlock(task);
210                 do {
211                         cpu_relax();
212                 } while (!write_can_lock(&tasklist_lock));
213                 goto repeat;
214         }
215
216         if (!task->mm)
217                 goto bad;
218         /* the same process cannot be attached many times */
219         if (task->ptrace & PT_PTRACED)
220                 goto bad;
221         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
222         if (retval)
223                 goto bad;
224
225         /* Go */
226         task->ptrace |= PT_PTRACED;
227         if (capable(CAP_SYS_PTRACE))
228                 task->ptrace |= PT_PTRACE_CAP;
229
230         __ptrace_link(task, current);
231
232         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
233 bad:
234         write_unlock_irqrestore(&tasklist_lock, flags);
235         task_unlock(task);
236         mutex_unlock(&task->cred_guard_mutex);
237 out:
238         return retval;
239 }
240
241 /*
242  * Called with irqs disabled, returns true if childs should reap themselves.
243  */
244 static int ignoring_children(struct sighand_struct *sigh)
245 {
246         int ret;
247         spin_lock(&sigh->siglock);
248         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
249               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
250         spin_unlock(&sigh->siglock);
251         return ret;
252 }
253
254 /*
255  * Called with tasklist_lock held for writing.
256  * Unlink a traced task, and clean it up if it was a traced zombie.
257  * Return true if it needs to be reaped with release_task().
258  * (We can't call release_task() here because we already hold tasklist_lock.)
259  *
260  * If it's a zombie, our attachedness prevented normal parent notification
261  * or self-reaping.  Do notification now if it would have happened earlier.
262  * If it should reap itself, return true.
263  *
264  * If it's our own child, there is no notification to do.
265  * But if our normal children self-reap, then this child
266  * was prevented by ptrace and we must reap it now.
267  */
268 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
269 {
270         __ptrace_unlink(p);
271
272         if (p->exit_state == EXIT_ZOMBIE) {
273                 if (!task_detached(p) && thread_group_empty(p)) {
274                         if (!same_thread_group(p->real_parent, tracer))
275                                 do_notify_parent(p, p->exit_signal);
276                         else if (ignoring_children(tracer->sighand))
277                                 p->exit_signal = -1;
278                 }
279                 if (task_detached(p)) {
280                         /* Mark it as in the process of being reaped. */
281                         p->exit_state = EXIT_DEAD;
282                         return true;
283                 }
284         }
285
286         return false;
287 }
288
289 int ptrace_detach(struct task_struct *child, unsigned int data)
290 {
291         bool dead = false;
292
293         if (!valid_signal(data))
294                 return -EIO;
295
296         /* Architecture-specific hardware disable .. */
297         ptrace_disable(child);
298         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
299
300         write_lock_irq(&tasklist_lock);
301         /*
302          * This child can be already killed. Make sure de_thread() or
303          * our sub-thread doing do_wait() didn't do release_task() yet.
304          */
305         if (child->ptrace) {
306                 child->exit_code = data;
307                 dead = __ptrace_detach(current, child);
308         }
309         write_unlock_irq(&tasklist_lock);
310
311         if (unlikely(dead))
312                 release_task(child);
313
314         return 0;
315 }
316
317 /*
318  * Detach all tasks we were using ptrace on.
319  */
320 void exit_ptrace(struct task_struct *tracer)
321 {
322         struct task_struct *p, *n;
323         LIST_HEAD(ptrace_dead);
324
325         write_lock_irq(&tasklist_lock);
326         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
327                 if (__ptrace_detach(tracer, p))
328                         list_add(&p->ptrace_entry, &ptrace_dead);
329         }
330         write_unlock_irq(&tasklist_lock);
331
332         BUG_ON(!list_empty(&tracer->ptraced));
333
334         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
335                 list_del_init(&p->ptrace_entry);
336                 release_task(p);
337         }
338 }
339
340 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
341 {
342         int copied = 0;
343
344         while (len > 0) {
345                 char buf[128];
346                 int this_len, retval;
347
348                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
349                 retval = access_process_vm(tsk, src, buf, this_len, 0);
350                 if (!retval) {
351                         if (copied)
352                                 break;
353                         return -EIO;
354                 }
355                 if (copy_to_user(dst, buf, retval))
356                         return -EFAULT;
357                 copied += retval;
358                 src += retval;
359                 dst += retval;
360                 len -= retval;
361         }
362         return copied;
363 }
364
365 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
366 {
367         int copied = 0;
368
369         while (len > 0) {
370                 char buf[128];
371                 int this_len, retval;
372
373                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
374                 if (copy_from_user(buf, src, this_len))
375                         return -EFAULT;
376                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
377                 if (!retval) {
378                         if (copied)
379                                 break;
380                         return -EIO;
381                 }
382                 copied += retval;
383                 src += retval;
384                 dst += retval;
385                 len -= retval;
386         }
387         return copied;
388 }
389
390 static int ptrace_setoptions(struct task_struct *child, long data)
391 {
392         child->ptrace &= ~PT_TRACE_MASK;
393
394         if (data & PTRACE_O_TRACESYSGOOD)
395                 child->ptrace |= PT_TRACESYSGOOD;
396
397         if (data & PTRACE_O_TRACEFORK)
398                 child->ptrace |= PT_TRACE_FORK;
399
400         if (data & PTRACE_O_TRACEVFORK)
401                 child->ptrace |= PT_TRACE_VFORK;
402
403         if (data & PTRACE_O_TRACECLONE)
404                 child->ptrace |= PT_TRACE_CLONE;
405
406         if (data & PTRACE_O_TRACEEXEC)
407                 child->ptrace |= PT_TRACE_EXEC;
408
409         if (data & PTRACE_O_TRACEVFORKDONE)
410                 child->ptrace |= PT_TRACE_VFORK_DONE;
411
412         if (data & PTRACE_O_TRACEEXIT)
413                 child->ptrace |= PT_TRACE_EXIT;
414
415         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
416 }
417
418 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
419 {
420         int error = -ESRCH;
421
422         read_lock(&tasklist_lock);
423         if (likely(child->sighand != NULL)) {
424                 error = -EINVAL;
425                 spin_lock_irq(&child->sighand->siglock);
426                 if (likely(child->last_siginfo != NULL)) {
427                         *info = *child->last_siginfo;
428                         error = 0;
429                 }
430                 spin_unlock_irq(&child->sighand->siglock);
431         }
432         read_unlock(&tasklist_lock);
433         return error;
434 }
435
436 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
437 {
438         int error = -ESRCH;
439
440         read_lock(&tasklist_lock);
441         if (likely(child->sighand != NULL)) {
442                 error = -EINVAL;
443                 spin_lock_irq(&child->sighand->siglock);
444                 if (likely(child->last_siginfo != NULL)) {
445                         *child->last_siginfo = *info;
446                         error = 0;
447                 }
448                 spin_unlock_irq(&child->sighand->siglock);
449         }
450         read_unlock(&tasklist_lock);
451         return error;
452 }
453
454
455 #ifdef PTRACE_SINGLESTEP
456 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
457 #else
458 #define is_singlestep(request)          0
459 #endif
460
461 #ifdef PTRACE_SINGLEBLOCK
462 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
463 #else
464 #define is_singleblock(request)         0
465 #endif
466
467 #ifdef PTRACE_SYSEMU
468 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
469 #else
470 #define is_sysemu_singlestep(request)   0
471 #endif
472
473 static int ptrace_resume(struct task_struct *child, long request, long data)
474 {
475         if (!valid_signal(data))
476                 return -EIO;
477
478         if (request == PTRACE_SYSCALL)
479                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
480         else
481                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
482
483 #ifdef TIF_SYSCALL_EMU
484         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
485                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
486         else
487                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
488 #endif
489
490         if (is_singleblock(request)) {
491                 if (unlikely(!arch_has_block_step()))
492                         return -EIO;
493                 user_enable_block_step(child);
494         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
495                 if (unlikely(!arch_has_single_step()))
496                         return -EIO;
497                 user_enable_single_step(child);
498         } else {
499                 user_disable_single_step(child);
500         }
501
502         child->exit_code = data;
503         wake_up_process(child);
504
505         return 0;
506 }
507
508 int ptrace_request(struct task_struct *child, long request,
509                    long addr, long data)
510 {
511         int ret = -EIO;
512         siginfo_t siginfo;
513
514         switch (request) {
515         case PTRACE_PEEKTEXT:
516         case PTRACE_PEEKDATA:
517                 return generic_ptrace_peekdata(child, addr, data);
518         case PTRACE_POKETEXT:
519         case PTRACE_POKEDATA:
520                 return generic_ptrace_pokedata(child, addr, data);
521
522 #ifdef PTRACE_OLDSETOPTIONS
523         case PTRACE_OLDSETOPTIONS:
524 #endif
525         case PTRACE_SETOPTIONS:
526                 ret = ptrace_setoptions(child, data);
527                 break;
528         case PTRACE_GETEVENTMSG:
529                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
530                 break;
531
532         case PTRACE_GETSIGINFO:
533                 ret = ptrace_getsiginfo(child, &siginfo);
534                 if (!ret)
535                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
536                                                    &siginfo);
537                 break;
538
539         case PTRACE_SETSIGINFO:
540                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
541                                    sizeof siginfo))
542                         ret = -EFAULT;
543                 else
544                         ret = ptrace_setsiginfo(child, &siginfo);
545                 break;
546
547         case PTRACE_DETACH:      /* detach a process that was attached. */
548                 ret = ptrace_detach(child, data);
549                 break;
550
551 #ifdef PTRACE_SINGLESTEP
552         case PTRACE_SINGLESTEP:
553 #endif
554 #ifdef PTRACE_SINGLEBLOCK
555         case PTRACE_SINGLEBLOCK:
556 #endif
557 #ifdef PTRACE_SYSEMU
558         case PTRACE_SYSEMU:
559         case PTRACE_SYSEMU_SINGLESTEP:
560 #endif
561         case PTRACE_SYSCALL:
562         case PTRACE_CONT:
563                 return ptrace_resume(child, request, data);
564
565         case PTRACE_KILL:
566                 if (child->exit_state)  /* already dead */
567                         return 0;
568                 return ptrace_resume(child, request, SIGKILL);
569
570         default:
571                 break;
572         }
573
574         return ret;
575 }
576
577 /**
578  * ptrace_traceme  --  helper for PTRACE_TRACEME
579  *
580  * Performs checks and sets PT_PTRACED.
581  * Should be used by all ptrace implementations for PTRACE_TRACEME.
582  */
583 int ptrace_traceme(void)
584 {
585         int ret = -EPERM;
586
587         /*
588          * Are we already being traced?
589          */
590 repeat:
591         task_lock(current);
592         if (!(current->ptrace & PT_PTRACED)) {
593                 /*
594                  * See ptrace_attach() comments about the locking here.
595                  */
596                 unsigned long flags;
597                 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
598                         task_unlock(current);
599                         do {
600                                 cpu_relax();
601                         } while (!write_can_lock(&tasklist_lock));
602                         goto repeat;
603                 }
604
605                 ret = security_ptrace_traceme(current->parent);
606
607                 /*
608                  * Check PF_EXITING to ensure ->real_parent has not passed
609                  * exit_ptrace(). Otherwise we don't report the error but
610                  * pretend ->real_parent untraces us right after return.
611                  */
612                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
613                         current->ptrace |= PT_PTRACED;
614                         __ptrace_link(current, current->real_parent);
615                 }
616
617                 write_unlock_irqrestore(&tasklist_lock, flags);
618         }
619         task_unlock(current);
620         return ret;
621 }
622
623 /**
624  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
625  * @pid:       process id to grab a task_struct reference of
626  *
627  * This function is a helper for ptrace implementations.  It checks
628  * permissions and then grabs a task struct for use of the actual
629  * ptrace implementation.
630  *
631  * Returns the task_struct for @pid or an ERR_PTR() on failure.
632  */
633 struct task_struct *ptrace_get_task_struct(pid_t pid)
634 {
635         struct task_struct *child;
636
637         read_lock(&tasklist_lock);
638         child = find_task_by_vpid(pid);
639         if (child)
640                 get_task_struct(child);
641
642         read_unlock(&tasklist_lock);
643         if (!child)
644                 return ERR_PTR(-ESRCH);
645         return child;
646 }
647
648 #ifndef arch_ptrace_attach
649 #define arch_ptrace_attach(child)       do { } while (0)
650 #endif
651
652 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
653 {
654         struct task_struct *child;
655         long ret;
656
657         /*
658          * This lock_kernel fixes a subtle race with suid exec
659          */
660         lock_kernel();
661         if (request == PTRACE_TRACEME) {
662                 ret = ptrace_traceme();
663                 if (!ret)
664                         arch_ptrace_attach(current);
665                 goto out;
666         }
667
668         child = ptrace_get_task_struct(pid);
669         if (IS_ERR(child)) {
670                 ret = PTR_ERR(child);
671                 goto out;
672         }
673
674         if (request == PTRACE_ATTACH) {
675                 ret = ptrace_attach(child);
676                 /*
677                  * Some architectures need to do book-keeping after
678                  * a ptrace attach.
679                  */
680                 if (!ret)
681                         arch_ptrace_attach(child);
682                 goto out_put_task_struct;
683         }
684
685         ret = ptrace_check_attach(child, request == PTRACE_KILL);
686         if (ret < 0)
687                 goto out_put_task_struct;
688
689         ret = arch_ptrace(child, request, addr, data);
690
691  out_put_task_struct:
692         put_task_struct(child);
693  out:
694         unlock_kernel();
695         return ret;
696 }
697
698 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
699 {
700         unsigned long tmp;
701         int copied;
702
703         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
704         if (copied != sizeof(tmp))
705                 return -EIO;
706         return put_user(tmp, (unsigned long __user *)data);
707 }
708
709 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
710 {
711         int copied;
712
713         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
714         return (copied == sizeof(data)) ? 0 : -EIO;
715 }
716
717 #if defined CONFIG_COMPAT
718 #include <linux/compat.h>
719
720 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
721                           compat_ulong_t addr, compat_ulong_t data)
722 {
723         compat_ulong_t __user *datap = compat_ptr(data);
724         compat_ulong_t word;
725         siginfo_t siginfo;
726         int ret;
727
728         switch (request) {
729         case PTRACE_PEEKTEXT:
730         case PTRACE_PEEKDATA:
731                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
732                 if (ret != sizeof(word))
733                         ret = -EIO;
734                 else
735                         ret = put_user(word, datap);
736                 break;
737
738         case PTRACE_POKETEXT:
739         case PTRACE_POKEDATA:
740                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
741                 ret = (ret != sizeof(data) ? -EIO : 0);
742                 break;
743
744         case PTRACE_GETEVENTMSG:
745                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
746                 break;
747
748         case PTRACE_GETSIGINFO:
749                 ret = ptrace_getsiginfo(child, &siginfo);
750                 if (!ret)
751                         ret = copy_siginfo_to_user32(
752                                 (struct compat_siginfo __user *) datap,
753                                 &siginfo);
754                 break;
755
756         case PTRACE_SETSIGINFO:
757                 memset(&siginfo, 0, sizeof siginfo);
758                 if (copy_siginfo_from_user32(
759                             &siginfo, (struct compat_siginfo __user *) datap))
760                         ret = -EFAULT;
761                 else
762                         ret = ptrace_setsiginfo(child, &siginfo);
763                 break;
764
765         default:
766                 ret = ptrace_request(child, request, addr, data);
767         }
768
769         return ret;
770 }
771
772 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
773                                   compat_long_t addr, compat_long_t data)
774 {
775         struct task_struct *child;
776         long ret;
777
778         /*
779          * This lock_kernel fixes a subtle race with suid exec
780          */
781         lock_kernel();
782         if (request == PTRACE_TRACEME) {
783                 ret = ptrace_traceme();
784                 goto out;
785         }
786
787         child = ptrace_get_task_struct(pid);
788         if (IS_ERR(child)) {
789                 ret = PTR_ERR(child);
790                 goto out;
791         }
792
793         if (request == PTRACE_ATTACH) {
794                 ret = ptrace_attach(child);
795                 /*
796                  * Some architectures need to do book-keeping after
797                  * a ptrace attach.
798                  */
799                 if (!ret)
800                         arch_ptrace_attach(child);
801                 goto out_put_task_struct;
802         }
803
804         ret = ptrace_check_attach(child, request == PTRACE_KILL);
805         if (!ret)
806                 ret = compat_arch_ptrace(child, request, addr, data);
807
808  out_put_task_struct:
809         put_task_struct(child);
810  out:
811         unlock_kernel();
812         return ret;
813 }
814 #endif  /* CONFIG_COMPAT */