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
  22 #include <asm/pgtable.h>
  23 #include <asm/uaccess.h>
  24
  25 /*
  26  * ptrace a task: make the debugger its new parent and
  27  * move it to the ptrace list.
  28  *
  29  * Must be called with the tasklist lock write-held.
  30  */
  31 void __ptrace_link(task_t *child, task_t *new_parent)
  32 {
  33         BUG_ON(!list_empty(&child->ptrace_list));
  34         if (child->parent == new_parent)
  35                 return;
  36         list_add(&child->ptrace_list, &child->parent->ptrace_children);
  37         remove_parent(child);
  38         child->parent = new_parent;
  39         add_parent(child);
  40 }
  41
  42 /*
  43  * Turn a tracing stop into a normal stop now, since with no tracer there
  44  * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
  45  * signal sent that would resume the child, but didn't because it was in
  46  * TASK_TRACED, resume it now.
  47  * Requires that irqs be disabled.
  48  */
  49 void ptrace_untrace(task_t *child)
  50 {
  51         spin_lock(&child->sighand->siglock);
  52         if (child->state == TASK_TRACED) {
  53                 if (child->signal->flags & SIGNAL_STOP_STOPPED) {
  54                         child->state = TASK_STOPPED;
  55                 } else {
  56                         signal_wake_up(child, 1);
  57                 }
  58         }
  59         spin_unlock(&child->sighand->siglock);
  60 }
  61
  62 /*
  63  * unptrace a task: move it back to its original parent and
  64  * remove it from the ptrace list.
  65  *
  66  * Must be called with the tasklist lock write-held.
  67  */
  68 void __ptrace_unlink(task_t *child)
  69 {
  70         BUG_ON(!child->ptrace);
  71
  72         child->ptrace = 0;
  73         if (!list_empty(&child->ptrace_list)) {
  74                 list_del_init(&child->ptrace_list);
  75                 remove_parent(child);
  76                 child->parent = child->real_parent;
  77                 add_parent(child);
  78         }
  79
  80         if (child->state == TASK_TRACED)
  81                 ptrace_untrace(child);
  82 }
  83
  84 /*
  85  * Check that we have indeed attached to the thing..
  86  */
  87 int ptrace_check_attach(struct task_struct *child, int kill)
  88 {
  89         int ret = -ESRCH;
  90
  91         /*
  92          * We take the read lock around doing both checks to close a
  93          * possible race where someone else was tracing our child and
  94          * detached between these two checks.  After this locked check,
  95          * we are sure that this is our traced child and that can only
  96          * be changed by us so it's not changing right after this.
  97          */
  98         read_lock(&tasklist_lock);
  99         if ((child->ptrace & PT_PTRACED) && child->parent == current &&
 100             (!(child->ptrace & PT_ATTACHED) || child->real_parent != current)
 101             && child->signal != NULL) {
 102                 ret = 0;
 103                 spin_lock_irq(&child->sighand->siglock);
 104                 if (child->state == TASK_STOPPED) {
 105                         child->state = TASK_TRACED;
 106                 } else if (child->state != TASK_TRACED && !kill) {
 107                         ret = -ESRCH;
 108                 }
 109                 spin_unlock_irq(&child->sighand->siglock);
 110         }
 111         read_unlock(&tasklist_lock);
 112
 113         if (!ret && !kill) {
 114                 wait_task_inactive(child);
 115         }
 116
 117         /* All systems go.. */
 118         return ret;
 119 }
 120
 121 static int may_attach(struct task_struct *task)
 122 {
 123         if (!task->mm)
 124                 return -EPERM;
 125         if (((current->uid != task->euid) ||
 126              (current->uid != task->suid) ||
 127              (current->uid != task->uid) ||
 128              (current->gid != task->egid) ||
 129              (current->gid != task->sgid) ||
 130              (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
 131                 return -EPERM;
 132         smp_rmb();
 133         if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
 134                 return -EPERM;
 135
 136         return security_ptrace(current, task);
 137 }
 138
 139 int ptrace_may_attach(struct task_struct *task)
 140 {
 141         int err;
 142         task_lock(task);
 143         err = may_attach(task);
 144         task_unlock(task);
 145         return !err;
 146 }
 147
 148 int ptrace_attach(struct task_struct *task)
 149 {
 150         int retval;
 151         task_lock(task);
 152         retval = -EPERM;
 153         if (task->pid <= 1)
 154                 goto bad;
 155         if (task->tgid == current->tgid)
 156                 goto bad;
 157         /* the same process cannot be attached many times */
 158         if (task->ptrace & PT_PTRACED)
 159                 goto bad;
 160         retval = may_attach(task);
 161         if (retval)
 162                 goto bad;
 163
 164         /* Go */
 165         task->ptrace |= PT_PTRACED | ((task->real_parent != current)
 166                                       ? PT_ATTACHED : 0);
 167         if (capable(CAP_SYS_PTRACE))
 168                 task->ptrace |= PT_PTRACE_CAP;
 169         task_unlock(task);
 170
 171         write_lock_irq(&tasklist_lock);
 172         __ptrace_link(task, current);
 173         write_unlock_irq(&tasklist_lock);
 174
 175         force_sig_specific(SIGSTOP, task);
 176         return 0;
 177
 178 bad:
 179         task_unlock(task);
 180         return retval;
 181 }
 182
 183 void __ptrace_detach(struct task_struct *child, unsigned int data)
 184 {
 185         child->exit_code = data;
 186         /* .. re-parent .. */
 187         __ptrace_unlink(child);
 188         /* .. and wake it up. */
 189         if (child->exit_state != EXIT_ZOMBIE)
 190                 wake_up_process(child);
 191 }
 192
 193 int ptrace_detach(struct task_struct *child, unsigned int data)
 194 {
 195         if (!valid_signal(data))
 196                 return -EIO;
 197
 198         /* Architecture-specific hardware disable .. */
 199         ptrace_disable(child);
 200
 201         write_lock_irq(&tasklist_lock);
 202         if (child->ptrace)
 203                 __ptrace_detach(child, data);
 204         write_unlock_irq(&tasklist_lock);
 205
 206         return 0;
 207 }
 208
 209 /*
 210  * Access another process' address space.
 211  * Source/target buffer must be kernel space,
 212  * Do not walk the page table directly, use get_user_pages
 213  */
 214
 215 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
 216 {
 217         struct mm_struct *mm;
 218         struct vm_area_struct *vma;
 219         struct page *page;
 220         void *old_buf = buf;
 221
 222         mm = get_task_mm(tsk);
 223         if (!mm)
 224                 return 0;
 225
 226         down_read(&mm->mmap_sem);
 227         /* ignore errors, just check how much was sucessfully transfered */
 228         while (len) {
 229                 int bytes, ret, offset;
 230                 void *maddr;
 231
 232                 ret = get_user_pages(tsk, mm, addr, 1,
 233                                 write, 1, &page, &vma);
 234                 if (ret <= 0)
 235                         break;
 236
 237                 bytes = len;
 238                 offset = addr & (PAGE_SIZE-1);
 239                 if (bytes > PAGE_SIZE-offset)
 240                         bytes = PAGE_SIZE-offset;
 241
 242                 maddr = kmap(page);
 243                 if (write) {
 244                         copy_to_user_page(vma, page, addr,
 245                                           maddr + offset, buf, bytes);
 246                         set_page_dirty_lock(page);
 247                 } else {
 248                         copy_from_user_page(vma, page, addr,
 249                                             buf, maddr + offset, bytes);
 250                 }
 251                 kunmap(page);
 252                 page_cache_release(page);
 253                 len -= bytes;
 254                 buf += bytes;
 255                 addr += bytes;
 256         }
 257         up_read(&mm->mmap_sem);
 258         mmput(mm);
 259
 260         return buf - old_buf;
 261 }
 262
 263 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 264 {
 265         int copied = 0;
 266
 267         while (len > 0) {
 268                 char buf[128];
 269                 int this_len, retval;
 270
 271                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 272                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 273                 if (!retval) {
 274                         if (copied)
 275                                 break;
 276                         return -EIO;
 277                 }
 278                 if (copy_to_user(dst, buf, retval))
 279                         return -EFAULT;
 280                 copied += retval;
 281                 src += retval;
 282                 dst += retval;
 283                 len -= retval;
 284         }
 285         return copied;
 286 }
 287
 288 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 289 {
 290         int copied = 0;
 291
 292         while (len > 0) {
 293                 char buf[128];
 294                 int this_len, retval;
 295
 296                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 297                 if (copy_from_user(buf, src, this_len))
 298                         return -EFAULT;
 299                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 300                 if (!retval) {
 301                         if (copied)
 302                                 break;
 303                         return -EIO;
 304                 }
 305                 copied += retval;
 306                 src += retval;
 307                 dst += retval;
 308                 len -= retval;
 309         }
 310         return copied;
 311 }
 312
 313 static int ptrace_setoptions(struct task_struct *child, long data)
 314 {
 315         child->ptrace &= ~PT_TRACE_MASK;
 316
 317         if (data & PTRACE_O_TRACESYSGOOD)
 318                 child->ptrace |= PT_TRACESYSGOOD;
 319
 320         if (data & PTRACE_O_TRACEFORK)
 321                 child->ptrace |= PT_TRACE_FORK;
 322
 323         if (data & PTRACE_O_TRACEVFORK)
 324                 child->ptrace |= PT_TRACE_VFORK;
 325
 326         if (data & PTRACE_O_TRACECLONE)
 327                 child->ptrace |= PT_TRACE_CLONE;
 328
 329         if (data & PTRACE_O_TRACEEXEC)
 330                 child->ptrace |= PT_TRACE_EXEC;
 331
 332         if (data & PTRACE_O_TRACEVFORKDONE)
 333                 child->ptrace |= PT_TRACE_VFORK_DONE;
 334
 335         if (data & PTRACE_O_TRACEEXIT)
 336                 child->ptrace |= PT_TRACE_EXIT;
 337
 338         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 339 }
 340
 341 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
 342 {
 343         siginfo_t lastinfo;
 344         int error = -ESRCH;
 345
 346         read_lock(&tasklist_lock);
 347         if (likely(child->sighand != NULL)) {
 348                 error = -EINVAL;
 349                 spin_lock_irq(&child->sighand->siglock);
 350                 if (likely(child->last_siginfo != NULL)) {
 351                         lastinfo = *child->last_siginfo;
 352                         error = 0;
 353                 }
 354                 spin_unlock_irq(&child->sighand->siglock);
 355         }
 356         read_unlock(&tasklist_lock);
 357         if (!error)
 358                 return copy_siginfo_to_user(data, &lastinfo);
 359         return error;
 360 }
 361
 362 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
 363 {
 364         siginfo_t newinfo;
 365         int error = -ESRCH;
 366
 367         if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
 368                 return -EFAULT;
 369
 370         read_lock(&tasklist_lock);
 371         if (likely(child->sighand != NULL)) {
 372                 error = -EINVAL;
 373                 spin_lock_irq(&child->sighand->siglock);
 374                 if (likely(child->last_siginfo != NULL)) {
 375                         *child->last_siginfo = newinfo;
 376                         error = 0;
 377                 }
 378                 spin_unlock_irq(&child->sighand->siglock);
 379         }
 380         read_unlock(&tasklist_lock);
 381         return error;
 382 }
 383
 384 int ptrace_request(struct task_struct *child, long request,
 385                    long addr, long data)
 386 {
 387         int ret = -EIO;
 388
 389         switch (request) {
 390 #ifdef PTRACE_OLDSETOPTIONS
 391         case PTRACE_OLDSETOPTIONS:
 392 #endif
 393         case PTRACE_SETOPTIONS:
 394                 ret = ptrace_setoptions(child, data);
 395                 break;
 396         case PTRACE_GETEVENTMSG:
 397                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 398                 break;
 399         case PTRACE_GETSIGINFO:
 400                 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
 401                 break;
 402         case PTRACE_SETSIGINFO:
 403                 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
 404                 break;
 405         default:
 406                 break;
 407         }
 408
 409         return ret;
 410 }
 411
 412 /**
 413  * ptrace_traceme  --  helper for PTRACE_TRACEME
 414  *
 415  * Performs checks and sets PT_PTRACED.
 416  * Should be used by all ptrace implementations for PTRACE_TRACEME.
 417  */
 418 int ptrace_traceme(void)
 419 {
 420         int ret;
 421
 422         /*
 423          * Are we already being traced?
 424          */
 425         if (current->ptrace & PT_PTRACED)
 426                 return -EPERM;
 427         ret = security_ptrace(current->parent, current);
 428         if (ret)
 429                 return -EPERM;
 430         /*
 431          * Set the ptrace bit in the process ptrace flags.
 432          */
 433         current->ptrace |= PT_PTRACED;
 434         return 0;
 435 }
 436
 437 /**
 438  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
 439  * @pid:       process id to grab a task_struct reference of
 440  *
 441  * This function is a helper for ptrace implementations.  It checks
 442  * permissions and then grabs a task struct for use of the actual
 443  * ptrace implementation.
 444  *
 445  * Returns the task_struct for @pid or an ERR_PTR() on failure.
 446  */
 447 struct task_struct *ptrace_get_task_struct(pid_t pid)
 448 {
 449         struct task_struct *child;
 450
 451         /*
 452          * Tracing init is not allowed.
 453          */
 454         if (pid == 1)
 455                 return ERR_PTR(-EPERM);
 456
 457         read_lock(&tasklist_lock);
 458         child = find_task_by_pid(pid);
 459         if (child)
 460                 get_task_struct(child);
 461         read_unlock(&tasklist_lock);
 462         if (!child)
 463                 return ERR_PTR(-ESRCH);
 464         return child;
 465 }
 466
 467 #ifndef __ARCH_SYS_PTRACE
 468 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
 469 {
 470         struct task_struct *child;
 471         long ret;
 472
 473         /*
 474          * This lock_kernel fixes a subtle race with suid exec
 475          */
 476         lock_kernel();
 477         if (request == PTRACE_TRACEME) {
 478                 ret = ptrace_traceme();
 479                 goto out;
 480         }
 481
 482         child = ptrace_get_task_struct(pid);
 483         if (IS_ERR(child)) {
 484                 ret = PTR_ERR(child);
 485                 goto out;
 486         }
 487
 488         if (request == PTRACE_ATTACH) {
 489                 ret = ptrace_attach(child);
 490                 goto out_put_task_struct;
 491         }
 492
 493         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 494         if (ret < 0)
 495                 goto out_put_task_struct;
 496
 497         ret = arch_ptrace(child, request, addr, data);
 498         if (ret < 0)
 499                 goto out_put_task_struct;
 500
 501  out_put_task_struct:
 502         put_task_struct(child);
 503  out:
 504         unlock_kernel();
 505         return ret;
 506 }
 507 #endif /* __ARCH_SYS_PTRACE */