linux-kernel - [PATCH 05/16] ptrace: Remove dead code from __ptrace

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Date:   Wed, 18 May 2022 17:53:44 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     linux-kernel@...r.kernel.org
Cc:     rjw@...ysocki.net, Oleg Nesterov <oleg@...hat.com>,
        mingo@...nel.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, mgorman@...e.de,
        bigeasy@...utronix.de, Will Deacon <will@...nel.org>,
        tj@...nel.org, linux-pm@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        linux-um@...ts.infradead.org, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        linux-xtensa@...ux-xtensa.org, Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>, linux-ia64@...r.kernel.org,
        Robert OCallahan <roc@...nos.co>, Kyle Huey <khuey@...nos.co>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Douglas Miller <dougmill@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 05/16] ptrace: Remove dead code from __ptrace_detach

Ever since commit 28d838cc4dfe ("Fix ptrace self-attach rule") it has
been impossible to attach another thread in the same thread group.

Remove the code from __ptrace_detach that was trying to support
detaching from a thread in the same thread group.  The code is
dead and I can not make sense of what it is trying to do.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 kernel/ptrace.c | 24 +++---------------------
 1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 328a34a99124..ca0e47691229 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -526,19 +526,6 @@ static int ptrace_traceme(void)
 	return ret;
 }
 
-/*
- * 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.
@@ -565,14 +552,9 @@ static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 
 	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);
-			dead = true;
-		}
-	}
+	if (!dead && thread_group_empty(p))
+		dead = do_notify_parent(p, p->exit_signal);
+
 	/* Mark it as in the process of being reaped. */
 	if (dead)
 		p->exit_state = EXIT_DEAD;
-- 
2.35.3