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Subject[tip: core/core] fork: Duplicate task_struct before stack allocation
The following commit has been merged into the core/core branch of tip:

Commit-ID: 546c42b2c5c161619736dd730d3df709181999d0
Gitweb: https://git.kernel.org/tip/546c42b2c5c161619736dd730d3df709181999d0
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Thu, 17 Feb 2022 11:24:00 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Tue, 22 Feb 2022 22:25:01 +01:00

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 for further changes.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20220217102406.3697941-3-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 f5cc101..30c01ce 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;

+ err = arch_dup_task_struct(tsk, orig);
+ if (err)
+ goto free_tsk;
+
stack = 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)

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
@@ -912,9 +914,6 @@ 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;
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