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
 171         audit_ptrace(task);
 172
 173         retval = -EPERM;
 174         if (unlikely(task->flags & PF_KTHREAD))
 175                 goto out;
 176         if (same_thread_group(task, current))
 177                 goto out;
 178
 179         /*
 180          * Protect exec's credential calculations against our interference;
 181          * interference; SUID, SGID and LSM creds get determined differently
 182          * under ptrace.
 183          */
 184         retval = mutex_lock_interruptible(&task->cred_guard_mutex);
 185         if (retval < 0)
 186                 goto out;
 187
 188         task_lock(task);
 189         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
 190         task_unlock(task);
 191         if (retval)
 192                 goto unlock_creds;
 193
 194         write_lock_irq(&tasklist_lock);
 195         retval = -EPERM;
 196         if (unlikely(task->exit_state))
 197                 goto unlock_tasklist;
 198         if (task->ptrace)
 199                 goto unlock_tasklist;
 200
 201         task->ptrace = PT_PTRACED;
 202         if (capable(CAP_SYS_PTRACE))
 203                 task->ptrace |= PT_PTRACE_CAP;
 204
 205         __ptrace_link(task, current);
 206         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
 207
 208         retval = 0;
 209 unlock_tasklist:
 210         write_unlock_irq(&tasklist_lock);
 211 unlock_creds:
 212         mutex_unlock(&task->cred_guard_mutex);
 213 out:
 214         return retval;
 215 }
 216
 217 /**
 218  * ptrace_traceme  --  helper for PTRACE_TRACEME
 219  *
 220  * Performs checks and sets PT_PTRACED.
 221  * Should be used by all ptrace implementations for PTRACE_TRACEME.
 222  */
 223 int ptrace_traceme(void)
 224 {
 225         int ret = -EPERM;
 226
 227         write_lock_irq(&tasklist_lock);
 228         /* Are we already being traced? */
 229         if (!current->ptrace) {
 230                 ret = security_ptrace_traceme(current->parent);
 231                 /*
 232                  * Check PF_EXITING to ensure ->real_parent has not passed
 233                  * exit_ptrace(). Otherwise we don't report the error but
 234                  * pretend ->real_parent untraces us right after return.
 235                  */
 236                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
 237                         current->ptrace = PT_PTRACED;
 238                         __ptrace_link(current, current->real_parent);
 239                 }
 240         }
 241         write_unlock_irq(&tasklist_lock);
 242
 243         return ret;
 244 }
 245
 246 /*
 247  * Called with irqs disabled, returns true if childs should reap themselves.
 248  */
 249 static int ignoring_children(struct sighand_struct *sigh)
 250 {
 251         int ret;
 252         spin_lock(&sigh->siglock);
 253         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
 254               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
 255         spin_unlock(&sigh->siglock);
 256         return ret;
 257 }
 258
 259 /*
 260  * Called with tasklist_lock held for writing.
 261  * Unlink a traced task, and clean it up if it was a traced zombie.
 262  * Return true if it needs to be reaped with release_task().
 263  * (We can't call release_task() here because we already hold tasklist_lock.)
 264  *
 265  * If it's a zombie, our attachedness prevented normal parent notification
 266  * or self-reaping.  Do notification now if it would have happened earlier.
 267  * If it should reap itself, return true.
 268  *
 269  * If it's our own child, there is no notification to do.
 270  * But if our normal children self-reap, then this child
 271  * was prevented by ptrace and we must reap it now.
 272  */
 273 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 274 {
 275         __ptrace_unlink(p);
 276
 277         if (p->exit_state == EXIT_ZOMBIE) {
 278                 if (!task_detached(p) && thread_group_empty(p)) {
 279                         if (!same_thread_group(p->real_parent, tracer))
 280                                 do_notify_parent(p, p->exit_signal);
 281                         else if (ignoring_children(tracer->sighand))
 282                                 p->exit_signal = -1;
 283                 }
 284                 if (task_detached(p)) {
 285                         /* Mark it as in the process of being reaped. */
 286                         p->exit_state = EXIT_DEAD;
 287                         return true;
 288                 }
 289         }
 290
 291         return false;
 292 }
 293
 294 int ptrace_detach(struct task_struct *child, unsigned int data)
 295 {
 296         bool dead = false;
 297
 298         if (!valid_signal(data))
 299                 return -EIO;
 300
 301         /* Architecture-specific hardware disable .. */
 302         ptrace_disable(child);
 303         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 304
 305         write_lock_irq(&tasklist_lock);
 306         /*
 307          * This child can be already killed. Make sure de_thread() or
 308          * our sub-thread doing do_wait() didn't do release_task() yet.
 309          */
 310         if (child->ptrace) {
 311                 child->exit_code = data;
 312                 dead = __ptrace_detach(current, child);
 313                 if (!child->exit_state)
 314                         wake_up_process(child);
 315         }
 316         write_unlock_irq(&tasklist_lock);
 317
 318         if (unlikely(dead))
 319                 release_task(child);
 320
 321         return 0;
 322 }
 323
 324 /*
 325  * Detach all tasks we were using ptrace on.
 326  */
 327 void exit_ptrace(struct task_struct *tracer)
 328 {
 329         struct task_struct *p, *n;
 330         LIST_HEAD(ptrace_dead);
 331
 332         write_lock_irq(&tasklist_lock);
 333         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
 334                 if (__ptrace_detach(tracer, p))
 335                         list_add(&p->ptrace_entry, &ptrace_dead);
 336         }
 337         write_unlock_irq(&tasklist_lock);
 338
 339         BUG_ON(!list_empty(&tracer->ptraced));
 340
 341         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
 342                 list_del_init(&p->ptrace_entry);
 343                 release_task(p);
 344         }
 345 }
 346
 347 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 348 {
 349         int copied = 0;
 350
 351         while (len > 0) {
 352                 char buf[128];
 353                 int this_len, retval;
 354
 355                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 356                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 357                 if (!retval) {
 358                         if (copied)
 359                                 break;
 360                         return -EIO;
 361                 }
 362                 if (copy_to_user(dst, buf, retval))
 363                         return -EFAULT;
 364                 copied += retval;
 365                 src += retval;
 366                 dst += retval;
 367                 len -= retval;
 368         }
 369         return copied;
 370 }
 371
 372 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 373 {
 374         int copied = 0;
 375
 376         while (len > 0) {
 377                 char buf[128];
 378                 int this_len, retval;
 379
 380                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 381                 if (copy_from_user(buf, src, this_len))
 382                         return -EFAULT;
 383                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 384                 if (!retval) {
 385                         if (copied)
 386                                 break;
 387                         return -EIO;
 388                 }
 389                 copied += retval;
 390                 src += retval;
 391                 dst += retval;
 392                 len -= retval;
 393         }
 394         return copied;
 395 }
 396
 397 static int ptrace_setoptions(struct task_struct *child, long data)
 398 {
 399         child->ptrace &= ~PT_TRACE_MASK;
 400
 401         if (data & PTRACE_O_TRACESYSGOOD)
 402                 child->ptrace |= PT_TRACESYSGOOD;
 403
 404         if (data & PTRACE_O_TRACEFORK)
 405                 child->ptrace |= PT_TRACE_FORK;
 406
 407         if (data & PTRACE_O_TRACEVFORK)
 408                 child->ptrace |= PT_TRACE_VFORK;
 409
 410         if (data & PTRACE_O_TRACECLONE)
 411                 child->ptrace |= PT_TRACE_CLONE;
 412
 413         if (data & PTRACE_O_TRACEEXEC)
 414                 child->ptrace |= PT_TRACE_EXEC;
 415
 416         if (data & PTRACE_O_TRACEVFORKDONE)
 417                 child->ptrace |= PT_TRACE_VFORK_DONE;
 418
 419         if (data & PTRACE_O_TRACEEXIT)
 420                 child->ptrace |= PT_TRACE_EXIT;
 421
 422         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 423 }
 424
 425 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 426 {
 427         unsigned long flags;
 428         int error = -ESRCH;
 429
 430         if (lock_task_sighand(child, &flags)) {
 431                 error = -EINVAL;
 432                 if (likely(child->last_siginfo != NULL)) {
 433                         *info = *child->last_siginfo;
 434                         error = 0;
 435                 }
 436                 unlock_task_sighand(child, &flags);
 437         }
 438         return error;
 439 }
 440
 441 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 442 {
 443         unsigned long flags;
 444         int error = -ESRCH;
 445
 446         if (lock_task_sighand(child, &flags)) {
 447                 error = -EINVAL;
 448                 if (likely(child->last_siginfo != NULL)) {
 449                         *child->last_siginfo = *info;
 450                         error = 0;
 451                 }
 452                 unlock_task_sighand(child, &flags);
 453         }
 454         return error;
 455 }
 456
 457
 458 #ifdef PTRACE_SINGLESTEP
 459 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
 460 #else
 461 #define is_singlestep(request)          0
 462 #endif
 463
 464 #ifdef PTRACE_SINGLEBLOCK
 465 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
 466 #else
 467 #define is_singleblock(request)         0
 468 #endif
 469
 470 #ifdef PTRACE_SYSEMU
 471 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
 472 #else
 473 #define is_sysemu_singlestep(request)   0
 474 #endif
 475
 476 static int ptrace_resume(struct task_struct *child, long request, long data)
 477 {
 478         if (!valid_signal(data))
 479                 return -EIO;
 480
 481         if (request == PTRACE_SYSCALL)
 482                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 483         else
 484                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 485
 486 #ifdef TIF_SYSCALL_EMU
 487         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
 488                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 489         else
 490                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 491 #endif
 492
 493         if (is_singleblock(request)) {
 494                 if (unlikely(!arch_has_block_step()))
 495                         return -EIO;
 496                 user_enable_block_step(child);
 497         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
 498                 if (unlikely(!arch_has_single_step()))
 499                         return -EIO;
 500                 user_enable_single_step(child);
 501         } else {
 502                 user_disable_single_step(child);
 503         }
 504
 505         child->exit_code = data;
 506         wake_up_process(child);
 507
 508         return 0;
 509 }
 510
 511 int ptrace_request(struct task_struct *child, long request,
 512                    long addr, long data)
 513 {
 514         int ret = -EIO;
 515         siginfo_t siginfo;
 516
 517         switch (request) {
 518         case PTRACE_PEEKTEXT:
 519         case PTRACE_PEEKDATA:
 520                 return generic_ptrace_peekdata(child, addr, data);
 521         case PTRACE_POKETEXT:
 522         case PTRACE_POKEDATA:
 523                 return generic_ptrace_pokedata(child, addr, data);
 524
 525 #ifdef PTRACE_OLDSETOPTIONS
 526         case PTRACE_OLDSETOPTIONS:
 527 #endif
 528         case PTRACE_SETOPTIONS:
 529                 ret = ptrace_setoptions(child, data);
 530                 break;
 531         case PTRACE_GETEVENTMSG:
 532                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 533                 break;
 534
 535         case PTRACE_GETSIGINFO:
 536                 ret = ptrace_getsiginfo(child, &siginfo);
 537                 if (!ret)
 538                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
 539                                                    &siginfo);
 540                 break;
 541
 542         case PTRACE_SETSIGINFO:
 543                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
 544                                    sizeof siginfo))
 545                         ret = -EFAULT;
 546                 else
 547                         ret = ptrace_setsiginfo(child, &siginfo);
 548                 break;
 549
 550         case PTRACE_DETACH:      /* detach a process that was attached. */
 551                 ret = ptrace_detach(child, data);
 552                 break;
 553
 554 #ifdef PTRACE_SINGLESTEP
 555         case PTRACE_SINGLESTEP:
 556 #endif
 557 #ifdef PTRACE_SINGLEBLOCK
 558         case PTRACE_SINGLEBLOCK:
 559 #endif
 560 #ifdef PTRACE_SYSEMU
 561         case PTRACE_SYSEMU:
 562         case PTRACE_SYSEMU_SINGLESTEP:
 563 #endif
 564         case PTRACE_SYSCALL:
 565         case PTRACE_CONT:
 566                 return ptrace_resume(child, request, data);
 567
 568         case PTRACE_KILL:
 569                 if (child->exit_state)  /* already dead */
 570                         return 0;
 571                 return ptrace_resume(child, request, SIGKILL);
 572
 573         default:
 574                 break;
 575         }
 576
 577         return ret;
 578 }
 579
 580 static struct task_struct *ptrace_get_task_struct(pid_t pid)
 581 {
 582         struct task_struct *child;
 583
 584         rcu_read_lock();
 585         child = find_task_by_vpid(pid);
 586         if (child)
 587                 get_task_struct(child);
 588         rcu_read_unlock();
 589
 590         if (!child)
 591                 return ERR_PTR(-ESRCH);
 592         return child;
 593 }
 594
 595 #ifndef arch_ptrace_attach
 596 #define arch_ptrace_attach(child)       do { } while (0)
 597 #endif
 598
 599 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
 600 {
 601         struct task_struct *child;
 602         long ret;
 603
 604         /*
 605          * This lock_kernel fixes a subtle race with suid exec
 606          */
 607         lock_kernel();
 608         if (request == PTRACE_TRACEME) {
 609                 ret = ptrace_traceme();
 610                 if (!ret)
 611                         arch_ptrace_attach(current);
 612                 goto out;
 613         }
 614
 615         child = ptrace_get_task_struct(pid);
 616         if (IS_ERR(child)) {
 617                 ret = PTR_ERR(child);
 618                 goto out;
 619         }
 620
 621         if (request == PTRACE_ATTACH) {
 622                 ret = ptrace_attach(child);
 623                 /*
 624                  * Some architectures need to do book-keeping after
 625                  * a ptrace attach.
 626                  */
 627                 if (!ret)
 628                         arch_ptrace_attach(child);
 629                 goto out_put_task_struct;
 630         }
 631
 632         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 633         if (ret < 0)
 634                 goto out_put_task_struct;
 635
 636         ret = arch_ptrace(child, request, addr, data);
 637
 638  out_put_task_struct:
 639         put_task_struct(child);
 640  out:
 641         unlock_kernel();
 642         return ret;
 643 }
 644
 645 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
 646 {
 647         unsigned long tmp;
 648         int copied;
 649
 650         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
 651         if (copied != sizeof(tmp))
 652                 return -EIO;
 653         return put_user(tmp, (unsigned long __user *)data);
 654 }
 655
 656 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
 657 {
 658         int copied;
 659
 660         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
 661         return (copied == sizeof(data)) ? 0 : -EIO;
 662 }
 663
 664 #if defined CONFIG_COMPAT
 665 #include <linux/compat.h>
 666
 667 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 668                           compat_ulong_t addr, compat_ulong_t data)
 669 {
 670         compat_ulong_t __user *datap = compat_ptr(data);
 671         compat_ulong_t word;
 672         siginfo_t siginfo;
 673         int ret;
 674
 675         switch (request) {
 676         case PTRACE_PEEKTEXT:
 677         case PTRACE_PEEKDATA:
 678                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
 679                 if (ret != sizeof(word))
 680                         ret = -EIO;
 681                 else
 682                         ret = put_user(word, datap);
 683                 break;
 684
 685         case PTRACE_POKETEXT:
 686         case PTRACE_POKEDATA:
 687                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
 688                 ret = (ret != sizeof(data) ? -EIO : 0);
 689                 break;
 690
 691         case PTRACE_GETEVENTMSG:
 692                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
 693                 break;
 694
 695         case PTRACE_GETSIGINFO:
 696                 ret = ptrace_getsiginfo(child, &siginfo);
 697                 if (!ret)
 698                         ret = copy_siginfo_to_user32(
 699                                 (struct compat_siginfo __user *) datap,
 700                                 &siginfo);
 701                 break;
 702
 703         case PTRACE_SETSIGINFO:
 704                 memset(&siginfo, 0, sizeof siginfo);
 705                 if (copy_siginfo_from_user32(
 706                             &siginfo, (struct compat_siginfo __user *) datap))
 707                         ret = -EFAULT;
 708                 else
 709                         ret = ptrace_setsiginfo(child, &siginfo);
 710                 break;
 711
 712         default:
 713                 ret = ptrace_request(child, request, addr, data);
 714         }
 715
 716         return ret;
 717 }
 718
 719 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 720                                   compat_long_t addr, compat_long_t data)
 721 {
 722         struct task_struct *child;
 723         long ret;
 724
 725         /*
 726          * This lock_kernel fixes a subtle race with suid exec
 727          */
 728         lock_kernel();
 729         if (request == PTRACE_TRACEME) {
 730                 ret = ptrace_traceme();
 731                 goto out;
 732         }
 733
 734         child = ptrace_get_task_struct(pid);
 735         if (IS_ERR(child)) {
 736                 ret = PTR_ERR(child);
 737                 goto out;
 738         }
 739
 740         if (request == PTRACE_ATTACH) {
 741                 ret = ptrace_attach(child);
 742                 /*
 743                  * Some architectures need to do book-keeping after
 744                  * a ptrace attach.
 745                  */
 746                 if (!ret)
 747                         arch_ptrace_attach(child);
 748                 goto out_put_task_struct;
 749         }
 750
 751         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 752         if (!ret)
 753                 ret = compat_arch_ptrace(child, request, addr, data);
 754
 755  out_put_task_struct:
 756         put_task_struct(child);
 757  out:
 758         unlock_kernel();
 759         return ret;
 760 }
 761 #endif  /* CONFIG_COMPAT */