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