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