From: Mateusz Guzik <mjguzik@gmail.com>
Date: Tue, 19 Nov 2024 14:35:26 +0000 (+0100)
Subject: get_task_exe_file: check PF_KTHREAD locklessly
X-Git-Tag: v6.14-rc1~78^2~92
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=51f8bd6db591689fa1c67628b4cfe9778e76be6d;p=linux-block.git

get_task_exe_file: check PF_KTHREAD locklessly

Same thing as 8ac5dc66599c ("get_task_mm: check PF_KTHREAD lockless")

Nowadays PF_KTHREAD is sticky and it was never protected by ->alloc_lock.
Move the PF_KTHREAD check outside of task_lock() section to make this code
more understandable.

Link: https://lkml.kernel.org/r/20241119143526.704986-1-mjguzik@gmail.com
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/kernel/fork.c b/kernel/fork.c
index 9b301180fd41..19d7fe31869b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1514,12 +1514,13 @@ struct file *get_task_exe_file(struct task_struct *task)
 	struct file *exe_file = NULL;
 	struct mm_struct *mm;
 
+	if (task->flags & PF_KTHREAD)
+		return NULL;
+
 	task_lock(task);
 	mm = task->mm;
-	if (mm) {
-		if (!(task->flags & PF_KTHREAD))
-			exe_file = get_mm_exe_file(mm);
-	}
+	if (mm)
+		exe_file = get_mm_exe_file(mm);
 	task_unlock(task);
 	return exe_file;
 }