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 /* May we inspect the given task? 124 * This check is used both for attaching with ptrace 125 * and for allowing access to sensitive information in /proc. 126 * 127 * ptrace_attach denies several cases that /proc allows 128 * because setting up the necessary parent/child relationship 129 * or halting the specified task is impossible. 130 */ 131 int dumpable = 0; 132 /* Don't let security modules deny introspection */ 133 if (task == current) 134 return 0; 135 if (((current->uid != task->euid) || 136 (current->uid != task->suid) || 137 (current->uid != task->uid) || 138 (current->gid != task->egid) || 139 (current->gid != task->sgid) || 140 (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE)) 141 return -EPERM; 142 smp_rmb(); 143 if (task->mm) 144 dumpable = task->mm->dumpable; 145 if (!dumpable && !capable(CAP_SYS_PTRACE)) 146 return -EPERM; 147 148 return security_ptrace(current, task); 149 } 150 151 int ptrace_may_attach(struct task_struct *task) 152 { 153 int err; 154 task_lock(task); 155 err = may_attach(task); 156 task_unlock(task); 157 return !err; 158 } 159 160 int ptrace_attach(struct task_struct *task) 161 { 162 int retval; 163 164 retval = -EPERM; 165 if (task->pid <= 1) 166 goto out; 167 if (task->tgid == current->tgid) 168 goto out; 169 170 repeat: 171 /* 172 * Nasty, nasty. 173 * 174 * We want to hold both the task-lock and the 175 * tasklist_lock for writing at the same time. 176 * But that's against the rules (tasklist_lock 177 * is taken for reading by interrupts on other 178 * cpu's that may have task_lock). 179 */ 180 task_lock(task); 181 local_irq_disable(); 182 if (!write_trylock(&tasklist_lock)) { 183 local_irq_enable(); 184 task_unlock(task); 185 do { 186 cpu_relax(); 187 } while (!write_can_lock(&tasklist_lock)); 188 goto repeat; 189 } 190 191 if (!task->mm) 192 goto bad; 193 /* the same process cannot be attached many times */ 194 if (task->ptrace & PT_PTRACED) 195 goto bad; 196 retval = may_attach(task); 197 if (retval) 198 goto bad; 199 200 /* Go */ 201 task->ptrace |= PT_PTRACED | ((task->real_parent != current) 202 ? PT_ATTACHED : 0); 203 if (capable(CAP_SYS_PTRACE)) 204 task->ptrace |= PT_PTRACE_CAP; 205 206 __ptrace_link(task, current); 207 208 force_sig_specific(SIGSTOP, task); 209 210 bad: 211 write_unlock_irq(&tasklist_lock); 212 task_unlock(task); 213 out: 214 return retval; 215 } 216 217 static inline void __ptrace_detach(struct task_struct *child, unsigned int data) 218 { 219 child->exit_code = data; 220 /* .. re-parent .. */ 221 __ptrace_unlink(child); 222 /* .. and wake it up. */ 223 if (child->exit_state != EXIT_ZOMBIE) 224 wake_up_process(child); 225 } 226 227 int ptrace_detach(struct task_struct *child, unsigned int data) 228 { 229 if (!valid_signal(data)) 230 return -EIO; 231 232 /* Architecture-specific hardware disable .. */ 233 ptrace_disable(child); 234 235 write_lock_irq(&tasklist_lock); 236 /* protect against de_thread()->release_task() */ 237 if (child->ptrace) 238 __ptrace_detach(child, data); 239 write_unlock_irq(&tasklist_lock); 240 241 return 0; 242 } 243 244 /* 245 * Access another process' address space. 246 * Source/target buffer must be kernel space, 247 * Do not walk the page table directly, use get_user_pages 248 */ 249 250 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write) 251 { 252 struct mm_struct *mm; 253 struct vm_area_struct *vma; 254 struct page *page; 255 void *old_buf = buf; 256 257 mm = get_task_mm(tsk); 258 if (!mm) 259 return 0; 260 261 down_read(&mm->mmap_sem); 262 /* ignore errors, just check how much was sucessfully transfered */ 263 while (len) { 264 int bytes, ret, offset; 265 void *maddr; 266 267 ret = get_user_pages(tsk, mm, addr, 1, 268 write, 1, &page, &vma); 269 if (ret <= 0) 270 break; 271 272 bytes = len; 273 offset = addr & (PAGE_SIZE-1); 274 if (bytes > PAGE_SIZE-offset) 275 bytes = PAGE_SIZE-offset; 276 277 maddr = kmap(page); 278 if (write) { 279 copy_to_user_page(vma, page, addr, 280 maddr + offset, buf, bytes); 281 set_page_dirty_lock(page); 282 } else { 283 copy_from_user_page(vma, page, addr, 284 buf, maddr + offset, bytes); 285 } 286 kunmap(page); 287 page_cache_release(page); 288 len -= bytes; 289 buf += bytes; 290 addr += bytes; 291 } 292 up_read(&mm->mmap_sem); 293 mmput(mm); 294 295 return buf - old_buf; 296 } 297 298 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len) 299 { 300 int copied = 0; 301 302 while (len > 0) { 303 char buf[128]; 304 int this_len, retval; 305 306 this_len = (len > sizeof(buf)) ? sizeof(buf) : len; 307 retval = access_process_vm(tsk, src, buf, this_len, 0); 308 if (!retval) { 309 if (copied) 310 break; 311 return -EIO; 312 } 313 if (copy_to_user(dst, buf, retval)) 314 return -EFAULT; 315 copied += retval; 316 src += retval; 317 dst += retval; 318 len -= retval; 319 } 320 return copied; 321 } 322 323 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len) 324 { 325 int copied = 0; 326 327 while (len > 0) { 328 char buf[128]; 329 int this_len, retval; 330 331 this_len = (len > sizeof(buf)) ? sizeof(buf) : len; 332 if (copy_from_user(buf, src, this_len)) 333 return -EFAULT; 334 retval = access_process_vm(tsk, dst, buf, this_len, 1); 335 if (!retval) { 336 if (copied) 337 break; 338 return -EIO; 339 } 340 copied += retval; 341 src += retval; 342 dst += retval; 343 len -= retval; 344 } 345 return copied; 346 } 347 348 static int ptrace_setoptions(struct task_struct *child, long data) 349 { 350 child->ptrace &= ~PT_TRACE_MASK; 351 352 if (data & PTRACE_O_TRACESYSGOOD) 353 child->ptrace |= PT_TRACESYSGOOD; 354 355 if (data & PTRACE_O_TRACEFORK) 356 child->ptrace |= PT_TRACE_FORK; 357 358 if (data & PTRACE_O_TRACEVFORK) 359 child->ptrace |= PT_TRACE_VFORK; 360 361 if (data & PTRACE_O_TRACECLONE) 362 child->ptrace |= PT_TRACE_CLONE; 363 364 if (data & PTRACE_O_TRACEEXEC) 365 child->ptrace |= PT_TRACE_EXEC; 366 367 if (data & PTRACE_O_TRACEVFORKDONE) 368 child->ptrace |= PT_TRACE_VFORK_DONE; 369 370 if (data & PTRACE_O_TRACEEXIT) 371 child->ptrace |= PT_TRACE_EXIT; 372 373 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0; 374 } 375 376 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data) 377 { 378 siginfo_t lastinfo; 379 int error = -ESRCH; 380 381 read_lock(&tasklist_lock); 382 if (likely(child->sighand != NULL)) { 383 error = -EINVAL; 384 spin_lock_irq(&child->sighand->siglock); 385 if (likely(child->last_siginfo != NULL)) { 386 lastinfo = *child->last_siginfo; 387 error = 0; 388 } 389 spin_unlock_irq(&child->sighand->siglock); 390 } 391 read_unlock(&tasklist_lock); 392 if (!error) 393 return copy_siginfo_to_user(data, &lastinfo); 394 return error; 395 } 396 397 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data) 398 { 399 siginfo_t newinfo; 400 int error = -ESRCH; 401 402 if (copy_from_user(&newinfo, data, sizeof (siginfo_t))) 403 return -EFAULT; 404 405 read_lock(&tasklist_lock); 406 if (likely(child->sighand != NULL)) { 407 error = -EINVAL; 408 spin_lock_irq(&child->sighand->siglock); 409 if (likely(child->last_siginfo != NULL)) { 410 *child->last_siginfo = newinfo; 411 error = 0; 412 } 413 spin_unlock_irq(&child->sighand->siglock); 414 } 415 read_unlock(&tasklist_lock); 416 return error; 417 } 418 419 int ptrace_request(struct task_struct *child, long request, 420 long addr, long data) 421 { 422 int ret = -EIO; 423 424 switch (request) { 425 #ifdef PTRACE_OLDSETOPTIONS 426 case PTRACE_OLDSETOPTIONS: 427 #endif 428 case PTRACE_SETOPTIONS: 429 ret = ptrace_setoptions(child, data); 430 break; 431 case PTRACE_GETEVENTMSG: 432 ret = put_user(child->ptrace_message, (unsigned long __user *) data); 433 break; 434 case PTRACE_GETSIGINFO: 435 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data); 436 break; 437 case PTRACE_SETSIGINFO: 438 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data); 439 break; 440 default: 441 break; 442 } 443 444 return ret; 445 } 446 447 /** 448 * ptrace_traceme -- helper for PTRACE_TRACEME 449 * 450 * Performs checks and sets PT_PTRACED. 451 * Should be used by all ptrace implementations for PTRACE_TRACEME. 452 */ 453 int ptrace_traceme(void) 454 { 455 int ret = -EPERM; 456 457 /* 458 * Are we already being traced? 459 */ 460 task_lock(current); 461 if (!(current->ptrace & PT_PTRACED)) { 462 ret = security_ptrace(current->parent, current); 463 /* 464 * Set the ptrace bit in the process ptrace flags. 465 */ 466 if (!ret) 467 current->ptrace |= PT_PTRACED; 468 } 469 task_unlock(current); 470 return ret; 471 } 472 473 /** 474 * ptrace_get_task_struct -- grab a task struct reference for ptrace 475 * @pid: process id to grab a task_struct reference of 476 * 477 * This function is a helper for ptrace implementations. It checks 478 * permissions and then grabs a task struct for use of the actual 479 * ptrace implementation. 480 * 481 * Returns the task_struct for @pid or an ERR_PTR() on failure. 482 */ 483 struct task_struct *ptrace_get_task_struct(pid_t pid) 484 { 485 struct task_struct *child; 486 487 /* 488 * Tracing init is not allowed. 489 */ 490 if (pid == 1) 491 return ERR_PTR(-EPERM); 492 493 read_lock(&tasklist_lock); 494 child = find_task_by_pid(pid); 495 if (child) 496 get_task_struct(child); 497 read_unlock(&tasklist_lock); 498 if (!child) 499 return ERR_PTR(-ESRCH); 500 return child; 501 } 502 503 #ifndef __ARCH_SYS_PTRACE 504 asmlinkage long sys_ptrace(long request, long pid, long addr, long data) 505 { 506 struct task_struct *child; 507 long ret; 508 509 /* 510 * This lock_kernel fixes a subtle race with suid exec 511 */ 512 lock_kernel(); 513 if (request == PTRACE_TRACEME) { 514 ret = ptrace_traceme(); 515 goto out; 516 } 517 518 child = ptrace_get_task_struct(pid); 519 if (IS_ERR(child)) { 520 ret = PTR_ERR(child); 521 goto out; 522 } 523 524 if (request == PTRACE_ATTACH) { 525 ret = ptrace_attach(child); 526 goto out_put_task_struct; 527 } 528 529 ret = ptrace_check_attach(child, request == PTRACE_KILL); 530 if (ret < 0) 531 goto out_put_task_struct; 532 533 ret = arch_ptrace(child, request, addr, data); 534 if (ret < 0) 535 goto out_put_task_struct; 536 537 out_put_task_struct: 538 put_task_struct(child); 539 out: 540 unlock_kernel(); 541 return ret; 542 } 543 #endif /* __ARCH_SYS_PTRACE */ 544