Commit f2f0b00a authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

ptrace: cleanup check/set of PT_PTRACED during attach 



ptrace_attach() and ptrace_traceme() are the last functions which look as
if the untraced task can have task->ptrace != 0, this must not be
possible.  Change the code to just check ->ptrace != 0 and s/|=/=/ to set
PT_PTRACED.

Also, a couple of trivial whitespace cleanups in ptrace_attach().

And move ptrace_traceme() up near ptrace_attach() to keep them close to
each other.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Acked-by: default avatarRoland 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 b79b7ba9

kernel/ptrace.c

+51 −50
Original line number Diff line number Diff line
@@ -177,7 +177,8 @@ int ptrace_attach(struct task_struct *task) 
	if (same_thread_group(task, current))

		goto out;



	/* Protect the target's credential calculations against our

	/*

	 * Protect exec's credential calculations against our interference;

	 * interference; SUID, SGID and LSM creds get determined differently

	 * under ptrace.

	 */
@@ -210,10 +211,10 @@ repeat: 
	retval = -EPERM;

	if (unlikely(task->exit_state))

		goto bad;

	if (task->ptrace & PT_PTRACED)

	if (task->ptrace)

		goto bad;



	task->ptrace |= PT_PTRACED;

	task->ptrace = PT_PTRACED;

	if (capable(CAP_SYS_PTRACE))

		task->ptrace |= PT_PTRACE_CAP;
@@ -229,6 +230,52 @@ out: 
	return retval;

}



/**

 * ptrace_traceme  --  helper for PTRACE_TRACEME

 *

 * Performs checks and sets PT_PTRACED.

 * Should be used by all ptrace implementations for PTRACE_TRACEME.

 */

int ptrace_traceme(void)

{

	int ret = -EPERM;



	/*

	 * Are we already being traced?

	 */

repeat:

	task_lock(current);

	if (!current->ptrace) {

		/*

		 * See ptrace_attach() comments about the locking here.

		 */

		unsigned long flags;

		if (!write_trylock_irqsave(&tasklist_lock, flags)) {

			task_unlock(current);

			do {

				cpu_relax();

			} while (!write_can_lock(&tasklist_lock));

			goto repeat;

		}



		ret = security_ptrace_traceme(current->parent);



		/*

		 * Check PF_EXITING to ensure ->real_parent has not passed

		 * exit_ptrace(). Otherwise we don't report the error but

		 * pretend ->real_parent untraces us right after return.

		 */

		if (!ret && !(current->real_parent->flags & PF_EXITING)) {

			current->ptrace = PT_PTRACED;

			__ptrace_link(current, current->real_parent);

		}



		write_unlock_irqrestore(&tasklist_lock, flags);

	}

	task_unlock(current);

	return ret;

}



/*

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

 */
@@ -567,52 +614,6 @@ int ptrace_request(struct task_struct *child, long request, 
	return ret;

}



/**

 * ptrace_traceme  --  helper for PTRACE_TRACEME

 *

 * Performs checks and sets PT_PTRACED.

 * Should be used by all ptrace implementations for PTRACE_TRACEME.

 */

int ptrace_traceme(void)

{

	int ret = -EPERM;



	/*

	 * Are we already being traced?

	 */

repeat:

	task_lock(current);

	if (!(current->ptrace & PT_PTRACED)) {

		/*

		 * See ptrace_attach() comments about the locking here.

		 */

		unsigned long flags;

		if (!write_trylock_irqsave(&tasklist_lock, flags)) {

			task_unlock(current);

			do {

				cpu_relax();

			} while (!write_can_lock(&tasklist_lock));

			goto repeat;

		}



		ret = security_ptrace_traceme(current->parent);



		/*

		 * Check PF_EXITING to ensure ->real_parent has not passed

		 * exit_ptrace(). Otherwise we don't report the error but

		 * pretend ->real_parent untraces us right after return.

		 */

		if (!ret && !(current->real_parent->flags & PF_EXITING)) {

			current->ptrace |= PT_PTRACED;

			__ptrace_link(current, current->real_parent);

		}



		write_unlock_irqrestore(&tasklist_lock, flags);

	}

	task_unlock(current);

	return ret;

}



/**

 * ptrace_get_task_struct  --  grab a task struct reference for ptrace

 * @pid:       process id to grab a task_struct reference of

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