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 9b301180fd41628f55fc318d8899cab2698ba6f5..19d7fe31869bf3055ef193ffd832409bf101abe3 100644 (file)
--- 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;
 }