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![Sukadev Bhattiprolu](/assets/img/avatar_default.png)
This is an updated version of Eric Biederman's is_init() patch. (http://lkml.org/lkml/2006/2/6/280). It applies cleanly to 2.6.18-rc3 and replaces a few more instances of ->pid == 1 with is_init(). Further, is_init() checks pid and thus removes dependency on Eric's other patches for now. Eric's original description: There are a lot of places in the kernel where we test for init because we give it special properties. Most significantly init must not die. This results in code all over the kernel test ->pid == 1. Introduce is_init to capture this case. With multiple pid spaces for all of the cases affected we are looking for only the first process on the system, not some other process that has pid == 1. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: Serge Hallyn <serue@us.ibm.com> Cc: Cedric Le Goater <clg@fr.ibm.com> Cc: <lxc-devel@lists.sourceforge.net> Acked-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
490 lines
11 KiB
C
490 lines
11 KiB
C
/*
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* linux/kernel/ptrace.c
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*
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* (C) Copyright 1999 Linus Torvalds
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*
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* Common interfaces for "ptrace()" which we do not want
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* to continually duplicate across every architecture.
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*/
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#include <linux/capability.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/errno.h>
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#include <linux/mm.h>
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#include <linux/highmem.h>
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#include <linux/pagemap.h>
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#include <linux/smp_lock.h>
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#include <linux/ptrace.h>
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#include <linux/security.h>
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#include <linux/signal.h>
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#include <asm/pgtable.h>
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#include <asm/uaccess.h>
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/*
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* ptrace a task: make the debugger its new parent and
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* move it to the ptrace list.
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*
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* Must be called with the tasklist lock write-held.
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*/
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void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
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{
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BUG_ON(!list_empty(&child->ptrace_list));
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if (child->parent == new_parent)
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return;
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list_add(&child->ptrace_list, &child->parent->ptrace_children);
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remove_parent(child);
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child->parent = new_parent;
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add_parent(child);
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}
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/*
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* Turn a tracing stop into a normal stop now, since with no tracer there
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* would be no way to wake it up with SIGCONT or SIGKILL. If there was a
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* signal sent that would resume the child, but didn't because it was in
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* TASK_TRACED, resume it now.
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* Requires that irqs be disabled.
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*/
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void ptrace_untrace(struct task_struct *child)
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{
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spin_lock(&child->sighand->siglock);
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if (child->state == TASK_TRACED) {
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if (child->signal->flags & SIGNAL_STOP_STOPPED) {
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child->state = TASK_STOPPED;
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} else {
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signal_wake_up(child, 1);
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}
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}
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spin_unlock(&child->sighand->siglock);
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}
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/*
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* unptrace a task: move it back to its original parent and
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* remove it from the ptrace list.
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*
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* Must be called with the tasklist lock write-held.
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*/
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void __ptrace_unlink(struct task_struct *child)
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{
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BUG_ON(!child->ptrace);
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child->ptrace = 0;
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if (!list_empty(&child->ptrace_list)) {
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list_del_init(&child->ptrace_list);
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remove_parent(child);
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child->parent = child->real_parent;
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add_parent(child);
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}
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if (child->state == TASK_TRACED)
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ptrace_untrace(child);
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}
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/*
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* Check that we have indeed attached to the thing..
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*/
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int ptrace_check_attach(struct task_struct *child, int kill)
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{
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int ret = -ESRCH;
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/*
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* We take the read lock around doing both checks to close a
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* possible race where someone else was tracing our child and
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* detached between these two checks. After this locked check,
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* we are sure that this is our traced child and that can only
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* be changed by us so it's not changing right after this.
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*/
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read_lock(&tasklist_lock);
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if ((child->ptrace & PT_PTRACED) && child->parent == current &&
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(!(child->ptrace & PT_ATTACHED) || child->real_parent != current)
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&& child->signal != NULL) {
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ret = 0;
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spin_lock_irq(&child->sighand->siglock);
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if (child->state == TASK_STOPPED) {
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child->state = TASK_TRACED;
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} else if (child->state != TASK_TRACED && !kill) {
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ret = -ESRCH;
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}
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spin_unlock_irq(&child->sighand->siglock);
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}
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read_unlock(&tasklist_lock);
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if (!ret && !kill) {
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wait_task_inactive(child);
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}
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/* All systems go.. */
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return ret;
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}
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static int may_attach(struct task_struct *task)
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{
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/* May we inspect the given task?
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* This check is used both for attaching with ptrace
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* and for allowing access to sensitive information in /proc.
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*
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* ptrace_attach denies several cases that /proc allows
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* because setting up the necessary parent/child relationship
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* or halting the specified task is impossible.
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*/
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int dumpable = 0;
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/* Don't let security modules deny introspection */
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if (task == current)
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return 0;
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if (((current->uid != task->euid) ||
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(current->uid != task->suid) ||
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(current->uid != task->uid) ||
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(current->gid != task->egid) ||
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(current->gid != task->sgid) ||
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(current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
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return -EPERM;
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smp_rmb();
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if (task->mm)
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dumpable = task->mm->dumpable;
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if (!dumpable && !capable(CAP_SYS_PTRACE))
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return -EPERM;
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return security_ptrace(current, task);
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}
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int ptrace_may_attach(struct task_struct *task)
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{
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int err;
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task_lock(task);
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err = may_attach(task);
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task_unlock(task);
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return !err;
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}
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int ptrace_attach(struct task_struct *task)
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{
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int retval;
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retval = -EPERM;
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if (task->pid <= 1)
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goto out;
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if (task->tgid == current->tgid)
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goto out;
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repeat:
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/*
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* Nasty, nasty.
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*
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* We want to hold both the task-lock and the
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* tasklist_lock for writing at the same time.
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* But that's against the rules (tasklist_lock
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* is taken for reading by interrupts on other
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* cpu's that may have task_lock).
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*/
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task_lock(task);
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local_irq_disable();
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if (!write_trylock(&tasklist_lock)) {
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local_irq_enable();
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task_unlock(task);
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do {
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cpu_relax();
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} while (!write_can_lock(&tasklist_lock));
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goto repeat;
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}
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if (!task->mm)
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goto bad;
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/* the same process cannot be attached many times */
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if (task->ptrace & PT_PTRACED)
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goto bad;
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retval = may_attach(task);
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if (retval)
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goto bad;
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/* Go */
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task->ptrace |= PT_PTRACED | ((task->real_parent != current)
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? PT_ATTACHED : 0);
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if (capable(CAP_SYS_PTRACE))
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task->ptrace |= PT_PTRACE_CAP;
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__ptrace_link(task, current);
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force_sig_specific(SIGSTOP, task);
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bad:
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write_unlock_irq(&tasklist_lock);
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task_unlock(task);
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out:
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return retval;
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}
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static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
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{
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child->exit_code = data;
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/* .. re-parent .. */
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__ptrace_unlink(child);
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/* .. and wake it up. */
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if (child->exit_state != EXIT_ZOMBIE)
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wake_up_process(child);
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}
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int ptrace_detach(struct task_struct *child, unsigned int data)
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{
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if (!valid_signal(data))
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return -EIO;
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/* Architecture-specific hardware disable .. */
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ptrace_disable(child);
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write_lock_irq(&tasklist_lock);
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/* protect against de_thread()->release_task() */
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if (child->ptrace)
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__ptrace_detach(child, data);
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write_unlock_irq(&tasklist_lock);
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return 0;
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}
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int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
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{
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int copied = 0;
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while (len > 0) {
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char buf[128];
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int this_len, retval;
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this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
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retval = access_process_vm(tsk, src, buf, this_len, 0);
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if (!retval) {
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if (copied)
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break;
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return -EIO;
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}
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if (copy_to_user(dst, buf, retval))
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return -EFAULT;
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copied += retval;
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src += retval;
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dst += retval;
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len -= retval;
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}
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return copied;
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}
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int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
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{
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int copied = 0;
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while (len > 0) {
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char buf[128];
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int this_len, retval;
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this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
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if (copy_from_user(buf, src, this_len))
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return -EFAULT;
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retval = access_process_vm(tsk, dst, buf, this_len, 1);
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if (!retval) {
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if (copied)
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break;
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return -EIO;
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}
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copied += retval;
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src += retval;
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dst += retval;
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len -= retval;
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}
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return copied;
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}
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static int ptrace_setoptions(struct task_struct *child, long data)
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{
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child->ptrace &= ~PT_TRACE_MASK;
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if (data & PTRACE_O_TRACESYSGOOD)
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child->ptrace |= PT_TRACESYSGOOD;
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if (data & PTRACE_O_TRACEFORK)
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child->ptrace |= PT_TRACE_FORK;
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if (data & PTRACE_O_TRACEVFORK)
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child->ptrace |= PT_TRACE_VFORK;
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if (data & PTRACE_O_TRACECLONE)
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child->ptrace |= PT_TRACE_CLONE;
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if (data & PTRACE_O_TRACEEXEC)
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child->ptrace |= PT_TRACE_EXEC;
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if (data & PTRACE_O_TRACEVFORKDONE)
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child->ptrace |= PT_TRACE_VFORK_DONE;
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if (data & PTRACE_O_TRACEEXIT)
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child->ptrace |= PT_TRACE_EXIT;
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return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
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}
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static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
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{
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siginfo_t lastinfo;
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int error = -ESRCH;
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read_lock(&tasklist_lock);
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if (likely(child->sighand != NULL)) {
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error = -EINVAL;
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spin_lock_irq(&child->sighand->siglock);
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if (likely(child->last_siginfo != NULL)) {
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lastinfo = *child->last_siginfo;
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error = 0;
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}
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spin_unlock_irq(&child->sighand->siglock);
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}
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read_unlock(&tasklist_lock);
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if (!error)
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return copy_siginfo_to_user(data, &lastinfo);
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return error;
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}
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static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
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{
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siginfo_t newinfo;
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int error = -ESRCH;
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if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
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return -EFAULT;
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read_lock(&tasklist_lock);
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if (likely(child->sighand != NULL)) {
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error = -EINVAL;
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spin_lock_irq(&child->sighand->siglock);
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if (likely(child->last_siginfo != NULL)) {
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*child->last_siginfo = newinfo;
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error = 0;
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}
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spin_unlock_irq(&child->sighand->siglock);
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}
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read_unlock(&tasklist_lock);
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return error;
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}
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int ptrace_request(struct task_struct *child, long request,
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long addr, long data)
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{
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int ret = -EIO;
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switch (request) {
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#ifdef PTRACE_OLDSETOPTIONS
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case PTRACE_OLDSETOPTIONS:
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#endif
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case PTRACE_SETOPTIONS:
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ret = ptrace_setoptions(child, data);
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break;
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case PTRACE_GETEVENTMSG:
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ret = put_user(child->ptrace_message, (unsigned long __user *) data);
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break;
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case PTRACE_GETSIGINFO:
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ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
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break;
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case PTRACE_SETSIGINFO:
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ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
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break;
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default:
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break;
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}
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return ret;
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}
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/**
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* ptrace_traceme -- helper for PTRACE_TRACEME
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*
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* Performs checks and sets PT_PTRACED.
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* Should be used by all ptrace implementations for PTRACE_TRACEME.
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*/
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int ptrace_traceme(void)
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{
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int ret = -EPERM;
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/*
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* Are we already being traced?
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*/
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task_lock(current);
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if (!(current->ptrace & PT_PTRACED)) {
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ret = security_ptrace(current->parent, current);
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/*
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* Set the ptrace bit in the process ptrace flags.
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*/
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if (!ret)
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current->ptrace |= PT_PTRACED;
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}
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task_unlock(current);
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return ret;
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}
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/**
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* ptrace_get_task_struct -- grab a task struct reference for ptrace
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* @pid: process id to grab a task_struct reference of
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*
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* This function is a helper for ptrace implementations. It checks
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* permissions and then grabs a task struct for use of the actual
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* ptrace implementation.
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*
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* Returns the task_struct for @pid or an ERR_PTR() on failure.
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*/
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struct task_struct *ptrace_get_task_struct(pid_t pid)
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{
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struct task_struct *child;
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/*
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* Tracing init is not allowed.
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*/
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if (pid == 1)
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return ERR_PTR(-EPERM);
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read_lock(&tasklist_lock);
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child = find_task_by_pid(pid);
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if (child)
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get_task_struct(child);
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read_unlock(&tasklist_lock);
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if (!child)
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return ERR_PTR(-ESRCH);
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return child;
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}
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#ifndef __ARCH_SYS_PTRACE
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asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
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{
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struct task_struct *child;
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long ret;
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/*
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* This lock_kernel fixes a subtle race with suid exec
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*/
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lock_kernel();
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if (request == PTRACE_TRACEME) {
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ret = ptrace_traceme();
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goto out;
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}
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child = ptrace_get_task_struct(pid);
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if (IS_ERR(child)) {
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ret = PTR_ERR(child);
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goto out;
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}
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if (request == PTRACE_ATTACH) {
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ret = ptrace_attach(child);
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goto out_put_task_struct;
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}
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ret = ptrace_check_attach(child, request == PTRACE_KILL);
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if (ret < 0)
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goto out_put_task_struct;
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ret = arch_ptrace(child, request, addr, data);
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if (ret < 0)
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goto out_put_task_struct;
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out_put_task_struct:
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put_task_struct(child);
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out:
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unlock_kernel();
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return ret;
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}
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#endif /* __ARCH_SYS_PTRACE */
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