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From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org
Cc:     Andy Lutomirski <luto@kernel.org>, Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: [PATCH 2/8] kernel/fork: Duplicate task_struct before stack allocation.
Date:   Tue, 25 Jan 2022 16:26:46 +0100
Message-Id: <20220125152652.1963111-3-bigeasy@linutronix.de>
In-Reply-To: <20220125152652.1963111-1-bigeasy@linutronix.de>
References: <20220125152652.1963111-1-bigeasy@linutronix.de>
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alloc_thread_stack_node() already populates the task_struct::stack
member except on IA64. The stack pointer is saved and populated again
because IA64 needs it and arch_dup_task_struct() overwrites it.

Allocate thread's stack after task_struct has been duplicated as a
preparation.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/fork.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index f63c0af6002da..c47dcba5d66d2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -888,6 +888,10 @@ static struct task_struct *dup_task_struct(struct task=
_struct *orig, int node)
 	if (!tsk)
 		return NULL;
=20
+	err =3D arch_dup_task_struct(tsk, orig);
+	if (err)
+		goto free_tsk;
+
 	stack =3D alloc_thread_stack_node(tsk, node);
 	if (!stack)
 		goto free_tsk;
@@ -897,8 +901,6 @@ static struct task_struct *dup_task_struct(struct task_=
struct *orig, int node)
=20
 	stack_vm_area =3D task_stack_vm_area(tsk);
=20
-	err =3D arch_dup_task_struct(tsk, orig);
-
 	/*
 	 * arch_dup_task_struct() clobbers the stack-related fields.  Make
 	 * sure they're properly initialized before using any stack-related
@@ -912,9 +914,6 @@ static struct task_struct *dup_task_struct(struct task_=
struct *orig, int node)
 	refcount_set(&tsk->stack_refcount, 1);
 #endif
=20
-	if (err)
-		goto free_stack;
-
 	err =3D scs_prepare(tsk, node);
 	if (err)
 		goto free_stack;
--=20
2.34.1