linux-kernel - [PATCH 3/8] __ptrace_detach: avoid task_detached(), check do_notify

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 22 Jun 2011 23:08:53 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	hch@...radead.org
Subject: [PATCH 3/8] __ptrace_detach: avoid task_detached(), check
	do_notify_parent()

__ptrace_detach() relies on the current obscure behaviour of
do_notify_parent(tsk) which changes tsk->exit_signal if this child
should be silently reaped. That is why we check task_detached(), it
is true if the task is sub-thread, or it is the group_leader but
its exit_signal was changed by do_notify_parent().

This is confusing, change the code to rely on !thread_group_leader()
or the value returned by do_notify_parent().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---

 kernel/ptrace.c |   33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

--- ptrace/kernel/ptrace.c~3_detach_ck_notify	2011-06-22 22:47:03.000000000 +0200
+++ ptrace/kernel/ptrace.c	2011-06-22 22:47:11.000000000 +0200
@@ -370,25 +370,28 @@ static int ignoring_children(struct sigh
  */
 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 {
+	bool dead;
+
 	__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)) {
-				__wake_up_parent(p, tracer);
-				p->exit_signal = -1;
-			}
-		}
-		if (task_detached(p)) {
-			/* Mark it as in the process of being reaped. */
-			p->exit_state = EXIT_DEAD;
-			return true;
+	if (p->exit_state != EXIT_ZOMBIE)
+		return false;
+
+	dead = !thread_group_leader(p);
+
+	if (!dead && thread_group_empty(p)) {
+		if (!same_thread_group(p->real_parent, tracer))
+			dead = do_notify_parent(p, p->exit_signal);
+		else if (ignoring_children(tracer->sighand)) {
+			__wake_up_parent(p, tracer);
+			p->exit_signal = -1;
+			dead = true;
 		}
 	}
-
-	return false;
+	/* Mark it as in the process of being reaped. */
+	if (dead)
+		p->exit_state = EXIT_DEAD;
+	return dead;
 }
 
 static int ptrace_detach(struct task_struct *child, unsigned int data)

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/