2 * linux/kernel/ptrace.c
4 * (C) Copyright 1999 Linus Torvalds
6 * Common interfaces for "ptrace()" which we do not want
7 * to continually duplicate across every architecture.
10 #include <linux/capability.h>
11 #include <linux/module.h>
12 #include <linux/sched.h>
13 #include <linux/errno.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 #include <linux/regset.h>
29 * ptrace a task: make the debugger its new parent and
30 * move it to the ptrace list.
32 * Must be called with the tasklist lock write-held.
34 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
36 BUG_ON(!list_empty(&child->ptrace_entry));
37 list_add(&child->ptrace_entry, &new_parent->ptraced);
38 child->parent = new_parent;
42 * Turn a tracing stop into a normal stop now, since with no tracer there
43 * would be no way to wake it up with SIGCONT or SIGKILL. If there was a
44 * signal sent that would resume the child, but didn't because it was in
45 * TASK_TRACED, resume it now.
46 * Requires that irqs be disabled.
48 static void ptrace_untrace(struct task_struct *child)
50 spin_lock(&child->sighand->siglock);
51 if (task_is_traced(child)) {
53 * If the group stop is completed or in progress,
54 * this thread was already counted as stopped.
56 if (child->signal->flags & SIGNAL_STOP_STOPPED ||
57 child->signal->group_stop_count)
58 __set_task_state(child, TASK_STOPPED);
60 signal_wake_up(child, 1);
62 spin_unlock(&child->sighand->siglock);
66 * unptrace a task: move it back to its original parent and
67 * remove it from the ptrace list.
69 * Must be called with the tasklist lock write-held.
71 void __ptrace_unlink(struct task_struct *child)
73 BUG_ON(!child->ptrace);
76 child->parent = child->real_parent;
77 list_del_init(&child->ptrace_entry);
79 if (task_is_traced(child))
80 ptrace_untrace(child);
84 * Check that we have indeed attached to the thing..
86 int ptrace_check_attach(struct task_struct *child, int kill)
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.
97 read_lock(&tasklist_lock);
98 if ((child->ptrace & PT_PTRACED) && child->parent == current) {
101 * child->sighand can't be NULL, release_task()
102 * does ptrace_unlink() before __exit_signal().
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)
109 spin_unlock_irq(&child->sighand->siglock);
111 read_unlock(&tasklist_lock);
114 ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;
116 /* All systems go.. */
120 int __ptrace_may_access(struct task_struct *task, unsigned int mode)
122 const struct cred *cred = current_cred(), *tcred;
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.
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.
133 /* Don't let security modules deny introspection */
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)) {
151 dumpable = get_dumpable(task->mm);
152 if (!dumpable && !capable(CAP_SYS_PTRACE))
155 return security_ptrace_access_check(task, mode);
158 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
162 err = __ptrace_may_access(task, mode);
167 int ptrace_attach(struct task_struct *task)
174 if (unlikely(task->flags & PF_KTHREAD))
176 if (same_thread_group(task, current))
180 * Protect exec's credential calculations against our interference;
181 * interference; SUID, SGID and LSM creds get determined differently
184 retval = -ERESTARTNOINTR;
185 if (mutex_lock_interruptible(&task->cred_guard_mutex))
189 retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
194 write_lock_irq(&tasklist_lock);
196 if (unlikely(task->exit_state))
197 goto unlock_tasklist;
199 goto unlock_tasklist;
201 task->ptrace = PT_PTRACED;
202 if (capable(CAP_SYS_PTRACE))
203 task->ptrace |= PT_PTRACE_CAP;
205 __ptrace_link(task, current);
206 send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
210 write_unlock_irq(&tasklist_lock);
212 mutex_unlock(&task->cred_guard_mutex);
218 * ptrace_traceme -- helper for PTRACE_TRACEME
220 * Performs checks and sets PT_PTRACED.
221 * Should be used by all ptrace implementations for PTRACE_TRACEME.
223 int ptrace_traceme(void)
227 write_lock_irq(&tasklist_lock);
228 /* Are we already being traced? */
229 if (!current->ptrace) {
230 ret = security_ptrace_traceme(current->parent);
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.
236 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
237 current->ptrace = PT_PTRACED;
238 __ptrace_link(current, current->real_parent);
241 write_unlock_irq(&tasklist_lock);
247 * Called with irqs disabled, returns true if childs should reap themselves.
249 static int ignoring_children(struct sighand_struct *sigh)
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);
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.)
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.
269 * If it's our own child, there is no notification to do. But if our normal
270 * children self-reap, then this child was prevented by ptrace and we must
271 * reap it now, in that case we must also wake up sub-threads sleeping in
274 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
278 if (p->exit_state == EXIT_ZOMBIE) {
279 if (!task_detached(p) && thread_group_empty(p)) {
280 if (!same_thread_group(p->real_parent, tracer))
281 do_notify_parent(p, p->exit_signal);
282 else if (ignoring_children(tracer->sighand)) {
283 __wake_up_parent(p, tracer);
287 if (task_detached(p)) {
288 /* Mark it as in the process of being reaped. */
289 p->exit_state = EXIT_DEAD;
297 int ptrace_detach(struct task_struct *child, unsigned int data)
301 if (!valid_signal(data))
304 /* Architecture-specific hardware disable .. */
305 ptrace_disable(child);
306 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
308 write_lock_irq(&tasklist_lock);
310 * This child can be already killed. Make sure de_thread() or
311 * our sub-thread doing do_wait() didn't do release_task() yet.
314 child->exit_code = data;
315 dead = __ptrace_detach(current, child);
316 if (!child->exit_state)
317 wake_up_process(child);
319 write_unlock_irq(&tasklist_lock);
328 * Detach all tasks we were using ptrace on.
330 void exit_ptrace(struct task_struct *tracer)
332 struct task_struct *p, *n;
333 LIST_HEAD(ptrace_dead);
335 write_lock_irq(&tasklist_lock);
336 list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
337 if (__ptrace_detach(tracer, p))
338 list_add(&p->ptrace_entry, &ptrace_dead);
340 write_unlock_irq(&tasklist_lock);
342 BUG_ON(!list_empty(&tracer->ptraced));
344 list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
345 list_del_init(&p->ptrace_entry);
350 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
356 int this_len, retval;
358 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
359 retval = access_process_vm(tsk, src, buf, this_len, 0);
365 if (copy_to_user(dst, buf, retval))
375 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
381 int this_len, retval;
383 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
384 if (copy_from_user(buf, src, this_len))
386 retval = access_process_vm(tsk, dst, buf, this_len, 1);
400 static int ptrace_setoptions(struct task_struct *child, long data)
402 child->ptrace &= ~PT_TRACE_MASK;
404 if (data & PTRACE_O_TRACESYSGOOD)
405 child->ptrace |= PT_TRACESYSGOOD;
407 if (data & PTRACE_O_TRACEFORK)
408 child->ptrace |= PT_TRACE_FORK;
410 if (data & PTRACE_O_TRACEVFORK)
411 child->ptrace |= PT_TRACE_VFORK;
413 if (data & PTRACE_O_TRACECLONE)
414 child->ptrace |= PT_TRACE_CLONE;
416 if (data & PTRACE_O_TRACEEXEC)
417 child->ptrace |= PT_TRACE_EXEC;
419 if (data & PTRACE_O_TRACEVFORKDONE)
420 child->ptrace |= PT_TRACE_VFORK_DONE;
422 if (data & PTRACE_O_TRACEEXIT)
423 child->ptrace |= PT_TRACE_EXIT;
425 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
428 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
433 if (lock_task_sighand(child, &flags)) {
435 if (likely(child->last_siginfo != NULL)) {
436 *info = *child->last_siginfo;
439 unlock_task_sighand(child, &flags);
444 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
449 if (lock_task_sighand(child, &flags)) {
451 if (likely(child->last_siginfo != NULL)) {
452 *child->last_siginfo = *info;
455 unlock_task_sighand(child, &flags);
461 #ifdef PTRACE_SINGLESTEP
462 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
464 #define is_singlestep(request) 0
467 #ifdef PTRACE_SINGLEBLOCK
468 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
470 #define is_singleblock(request) 0
474 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
476 #define is_sysemu_singlestep(request) 0
479 static int ptrace_resume(struct task_struct *child, long request, long data)
481 if (!valid_signal(data))
484 if (request == PTRACE_SYSCALL)
485 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
487 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
489 #ifdef TIF_SYSCALL_EMU
490 if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
491 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
493 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
496 if (is_singleblock(request)) {
497 if (unlikely(!arch_has_block_step()))
499 user_enable_block_step(child);
500 } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
501 if (unlikely(!arch_has_single_step()))
503 user_enable_single_step(child);
505 user_disable_single_step(child);
508 child->exit_code = data;
509 wake_up_process(child);
514 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
516 static const struct user_regset *
517 find_regset(const struct user_regset_view *view, unsigned int type)
519 const struct user_regset *regset;
522 for (n = 0; n < view->n; ++n) {
523 regset = view->regsets + n;
524 if (regset->core_note_type == type)
531 static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
534 const struct user_regset_view *view = task_user_regset_view(task);
535 const struct user_regset *regset = find_regset(view, type);
538 if (!regset || (kiov->iov_len % regset->size) != 0)
541 regset_no = regset - view->regsets;
542 kiov->iov_len = min(kiov->iov_len,
543 (__kernel_size_t) (regset->n * regset->size));
545 if (req == PTRACE_GETREGSET)
546 return copy_regset_to_user(task, view, regset_no, 0,
547 kiov->iov_len, kiov->iov_base);
549 return copy_regset_from_user(task, view, regset_no, 0,
550 kiov->iov_len, kiov->iov_base);
555 int ptrace_request(struct task_struct *child, long request,
556 long addr, long data)
562 case PTRACE_PEEKTEXT:
563 case PTRACE_PEEKDATA:
564 return generic_ptrace_peekdata(child, addr, data);
565 case PTRACE_POKETEXT:
566 case PTRACE_POKEDATA:
567 return generic_ptrace_pokedata(child, addr, data);
569 #ifdef PTRACE_OLDSETOPTIONS
570 case PTRACE_OLDSETOPTIONS:
572 case PTRACE_SETOPTIONS:
573 ret = ptrace_setoptions(child, data);
575 case PTRACE_GETEVENTMSG:
576 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
579 case PTRACE_GETSIGINFO:
580 ret = ptrace_getsiginfo(child, &siginfo);
582 ret = copy_siginfo_to_user((siginfo_t __user *) data,
586 case PTRACE_SETSIGINFO:
587 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
591 ret = ptrace_setsiginfo(child, &siginfo);
594 case PTRACE_DETACH: /* detach a process that was attached. */
595 ret = ptrace_detach(child, data);
598 #ifdef PTRACE_SINGLESTEP
599 case PTRACE_SINGLESTEP:
601 #ifdef PTRACE_SINGLEBLOCK
602 case PTRACE_SINGLEBLOCK:
606 case PTRACE_SYSEMU_SINGLESTEP:
610 return ptrace_resume(child, request, data);
613 if (child->exit_state) /* already dead */
615 return ptrace_resume(child, request, SIGKILL);
617 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
618 case PTRACE_GETREGSET:
619 case PTRACE_SETREGSET:
622 struct iovec __user *uiov = (struct iovec __user *) data;
624 if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov)))
627 if (__get_user(kiov.iov_base, &uiov->iov_base) ||
628 __get_user(kiov.iov_len, &uiov->iov_len))
631 ret = ptrace_regset(child, request, addr, &kiov);
633 ret = __put_user(kiov.iov_len, &uiov->iov_len);
644 static struct task_struct *ptrace_get_task_struct(pid_t pid)
646 struct task_struct *child;
649 child = find_task_by_vpid(pid);
651 get_task_struct(child);
655 return ERR_PTR(-ESRCH);
659 #ifndef arch_ptrace_attach
660 #define arch_ptrace_attach(child) do { } while (0)
663 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
665 struct task_struct *child;
669 * This lock_kernel fixes a subtle race with suid exec
672 if (request == PTRACE_TRACEME) {
673 ret = ptrace_traceme();
675 arch_ptrace_attach(current);
679 child = ptrace_get_task_struct(pid);
681 ret = PTR_ERR(child);
685 if (request == PTRACE_ATTACH) {
686 ret = ptrace_attach(child);
688 * Some architectures need to do book-keeping after
692 arch_ptrace_attach(child);
693 goto out_put_task_struct;
696 ret = ptrace_check_attach(child, request == PTRACE_KILL);
698 goto out_put_task_struct;
700 ret = arch_ptrace(child, request, addr, data);
703 put_task_struct(child);
709 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
714 copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
715 if (copied != sizeof(tmp))
717 return put_user(tmp, (unsigned long __user *)data);
720 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
724 copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
725 return (copied == sizeof(data)) ? 0 : -EIO;
728 #if defined CONFIG_COMPAT
729 #include <linux/compat.h>
731 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
732 compat_ulong_t addr, compat_ulong_t data)
734 compat_ulong_t __user *datap = compat_ptr(data);
740 case PTRACE_PEEKTEXT:
741 case PTRACE_PEEKDATA:
742 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
743 if (ret != sizeof(word))
746 ret = put_user(word, datap);
749 case PTRACE_POKETEXT:
750 case PTRACE_POKEDATA:
751 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
752 ret = (ret != sizeof(data) ? -EIO : 0);
755 case PTRACE_GETEVENTMSG:
756 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
759 case PTRACE_GETSIGINFO:
760 ret = ptrace_getsiginfo(child, &siginfo);
762 ret = copy_siginfo_to_user32(
763 (struct compat_siginfo __user *) datap,
767 case PTRACE_SETSIGINFO:
768 memset(&siginfo, 0, sizeof siginfo);
769 if (copy_siginfo_from_user32(
770 &siginfo, (struct compat_siginfo __user *) datap))
773 ret = ptrace_setsiginfo(child, &siginfo);
775 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
776 case PTRACE_GETREGSET:
777 case PTRACE_SETREGSET:
780 struct compat_iovec __user *uiov =
781 (struct compat_iovec __user *) datap;
785 if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov)))
788 if (__get_user(ptr, &uiov->iov_base) ||
789 __get_user(len, &uiov->iov_len))
792 kiov.iov_base = compat_ptr(ptr);
795 ret = ptrace_regset(child, request, addr, &kiov);
797 ret = __put_user(kiov.iov_len, &uiov->iov_len);
803 ret = ptrace_request(child, request, addr, data);
809 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
810 compat_long_t addr, compat_long_t data)
812 struct task_struct *child;
816 * This lock_kernel fixes a subtle race with suid exec
819 if (request == PTRACE_TRACEME) {
820 ret = ptrace_traceme();
824 child = ptrace_get_task_struct(pid);
826 ret = PTR_ERR(child);
830 if (request == PTRACE_ATTACH) {
831 ret = ptrace_attach(child);
833 * Some architectures need to do book-keeping after
837 arch_ptrace_attach(child);
838 goto out_put_task_struct;
841 ret = ptrace_check_attach(child, request == PTRACE_KILL);
843 ret = compat_arch_ptrace(child, request, addr, data);
846 put_task_struct(child);
851 #endif /* CONFIG_COMPAT */