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Commit 39c626ae authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

forget_original_parent: split out the un-ptrace part 



By discussion with Roland.

- Rename ptrace_exit() to exit_ptrace(), and change it to do all the
  necessary work with ->ptraced list by its own.

- Move this code from exit.c to ptrace.c

- Update the comment in ptrace_detach() to explain the rechecking of
  the child->ptrace.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Metzger, Markus T" <markus.t.metzger@intel.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7f5d3652

include/linux/ptrace.h

+1 −1
Original line number Diff line number Diff line
@@ -94,7 +94,7 @@ extern void ptrace_notify(int exit_code); 
extern void __ptrace_link(struct task_struct *child,

			  struct task_struct *new_parent);

extern void __ptrace_unlink(struct task_struct *child);

extern int __ptrace_detach(struct task_struct *tracer, struct task_struct *p);

extern void exit_ptrace(struct task_struct *tracer);

extern void ptrace_fork(struct task_struct *task, unsigned long clone_flags);

#define PTRACE_MODE_READ   1

#define PTRACE_MODE_ATTACH 2

include/linux/sched.h

+5 −0
Original line number Diff line number Diff line
@@ -2061,6 +2061,11 @@ static inline int thread_group_empty(struct task_struct *p) 
#define delay_group_leader(p) \

		(thread_group_leader(p) && !thread_group_empty(p))



static inline int task_detached(struct task_struct *p)

{

	return p->exit_signal == -1;

}



/*

 * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring

 * subscriptions and synchronises with wait4().  Also used in procfs.  Also

kernel/exit.c

+6 −89
Original line number Diff line number Diff line
@@ -61,11 +61,6 @@ DEFINE_TRACE(sched_process_wait); 


static void exit_mm(struct task_struct * tsk);



static inline int task_detached(struct task_struct *p)

{

	return p->exit_signal == -1;

}



static void __unhash_process(struct task_struct *p)

{

	nr_threads--;
@@ -731,85 +726,6 @@ static void exit_mm(struct task_struct * tsk) 
	mmput(mm);

}



/*

 * Called with irqs disabled, returns true if childs should reap themselves.

 */

static int ignoring_children(struct sighand_struct *sigh)

{

	int ret;

	spin_lock(&sigh->siglock);

	ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||

	      (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);

	spin_unlock(&sigh->siglock);

	return ret;

}



/* Returns nonzero if the tracee should be released. */

int __ptrace_detach(struct task_struct *tracer, struct task_struct *p)

{

	__ptrace_unlink(p);



	if (p->exit_state != EXIT_ZOMBIE)

		return 0;

	/*

	 * If it's a zombie, our attachedness prevented normal

	 * parent notification or self-reaping.  Do notification

	 * now if it would have happened earlier.  If it should

	 * reap itself we return true.

	 *

	 * If it's our own child, there is no notification to do.

	 * But if our normal children self-reap, then this child

	 * was prevented by ptrace and we must reap it now.

	 */

	if (!task_detached(p) && thread_group_empty(p)) {

		if (!same_thread_group(p->real_parent, tracer))

			do_notify_parent(p, p->exit_signal);

		else if (ignoring_children(tracer->sighand))

			p->exit_signal = -1;

	}



	if (!task_detached(p))

		return 0;



	/* Mark it as in the process of being reaped. */

	p->exit_state = EXIT_DEAD;

	return 1;

}



/*

 * Detach all tasks we were using ptrace on.

 * Any that need to be release_task'd are put on the @dead list.

 *

 * Called with write_lock(&tasklist_lock) held.

 */

static void ptrace_exit(struct task_struct *parent, struct list_head *dead)

{

	struct task_struct *p, *n;



	list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {

		if (__ptrace_detach(parent, p))

			list_add(&p->ptrace_entry, dead);

	}

}



/*

 * Finish up exit-time ptrace cleanup.

 *

 * Called without locks.

 */

static void ptrace_exit_finish(struct task_struct *parent,

			       struct list_head *dead)

{

	struct task_struct *p, *n;



	BUG_ON(!list_empty(&parent->ptraced));



	list_for_each_entry_safe(p, n, dead, ptrace_entry) {

		list_del_init(&p->ptrace_entry);

		release_task(p);

	}

}



/* Returns nonzero if the child should be released. */

static int reparent_thread(struct task_struct *p, struct task_struct *father)

{
@@ -894,12 +810,10 @@ static void forget_original_parent(struct task_struct *father) 
	struct task_struct *p, *n, *reaper;

	LIST_HEAD(ptrace_dead);



	exit_ptrace(father);



	write_lock_irq(&tasklist_lock);

	reaper = find_new_reaper(father);

	/*

	 * First clean up ptrace if we were using it.

	 */

	ptrace_exit(father, &ptrace_dead);



	list_for_each_entry_safe(p, n, &father->children, sibling) {

		p->real_parent = reaper;
@@ -914,7 +828,10 @@ static void forget_original_parent(struct task_struct *father) 
	write_unlock_irq(&tasklist_lock);

	BUG_ON(!list_empty(&father->children));



	ptrace_exit_finish(father, &ptrace_dead);

	list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {

		list_del_init(&p->ptrace_entry);

		release_task(p);

	}

}



/*

kernel/ptrace.c

+76 −2
Original line number Diff line number Diff line
@@ -235,9 +235,57 @@ out: 
	return retval;

}



/*

 * Called with irqs disabled, returns true if childs should reap themselves.

 */

static int ignoring_children(struct sighand_struct *sigh)

{

	int ret;

	spin_lock(&sigh->siglock);

	ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||

	      (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);

	spin_unlock(&sigh->siglock);

	return ret;

}



/*

 * Called with tasklist_lock held for writing.

 * Unlink a traced task, and clean it up if it was a traced zombie.

 * Return true if it needs to be reaped with release_task().

 * (We can't call release_task() here because we already hold tasklist_lock.)

 *

 * If it's a zombie, our attachedness prevented normal parent notification

 * or self-reaping.  Do notification now if it would have happened earlier.

 * If it should reap itself, return true.

 *

 * If it's our own child, there is no notification to do.

 * But if our normal children self-reap, then this child

 * was prevented by ptrace and we must reap it now.

 */

static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)

{

	__ptrace_unlink(p);



	if (p->exit_state == EXIT_ZOMBIE) {

		if (!task_detached(p) && thread_group_empty(p)) {

			if (!same_thread_group(p->real_parent, tracer))

				do_notify_parent(p, p->exit_signal);

			else if (ignoring_children(tracer->sighand))

				p->exit_signal = -1;

		}

		if (task_detached(p)) {

			/* Mark it as in the process of being reaped. */

			p->exit_state = EXIT_DEAD;

			return true;

		}

	}



	return false;

}



int ptrace_detach(struct task_struct *child, unsigned int data)

{

	int dead = 0;

	bool dead = false;



	if (!valid_signal(data))

		return -EIO;
@@ -247,7 +295,10 @@ int ptrace_detach(struct task_struct *child, unsigned int data) 
	clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);



	write_lock_irq(&tasklist_lock);

	/* protect against de_thread()->release_task() */

	/*

	 * This child can be already killed. Make sure de_thread() or

	 * our sub-thread doing do_wait() didn't do release_task() yet.

	 */

	if (child->ptrace) {

		child->exit_code = data;
@@ -264,6 +315,29 @@ int ptrace_detach(struct task_struct *child, unsigned int data) 
	return 0;

}



/*

 * Detach all tasks we were using ptrace on.

 */

void exit_ptrace(struct task_struct *tracer)

{

	struct task_struct *p, *n;

	LIST_HEAD(ptrace_dead);



	write_lock_irq(&tasklist_lock);

	list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {

		if (__ptrace_detach(tracer, p))

			list_add(&p->ptrace_entry, &ptrace_dead);

	}

	write_unlock_irq(&tasklist_lock);



	BUG_ON(!list_empty(&tracer->ptraced));



	list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {

		list_del_init(&p->ptrace_entry);

		release_task(p);

	}

}



int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)

{

	int copied = 0;