linux-kernel - [PATCH 2/8] kernel/fork: Duplicate task

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Message-Id: <20211118143452.136421-3-bigeasy@linutronix.de>
Date:   Thu, 18 Nov 2021 15:34:46 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org, linux-ia64@...r.kernel.org
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 2/8] kernel/fork: Duplicate task_struct before stack allocation.

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@...utronix.de>
---
 kernel/fork.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index bb3f2980f94fb..ce320d4b8e1f4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -887,6 +887,10 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	if (!tsk)
 		return NULL;
 
+	err = arch_dup_task_struct(tsk, orig);
+	if (err)
+		goto free_tsk;
+
 	stack = alloc_thread_stack_node(tsk, node);
 	if (!stack)
 		goto free_tsk;
@@ -896,8 +900,6 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 
 	stack_vm_area = task_stack_vm_area(tsk);
 
-	err = 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
@@ -911,9 +913,6 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	refcount_set(&tsk->stack_refcount, 1);
 #endif
 
-	if (err)
-		goto free_stack;
-
 	err = scs_prepare(tsk, node);
 	if (err)
 		goto free_stack;
-- 
2.33.1