On Tue, Jul 14, 2026 at 05:38:07PM +0200, Jann Horn wrote:
> diff --git a/include/linux/task_work.h b/include/linux/task_work.h
> index 0646804860ff..ce19fc14060c 100644
> --- a/include/linux/task_work.h
> +++ b/include/linux/task_work.h
> @@ -33,6 +33,7 @@ struct callback_head *task_work_cancel_match(struct
> task_struct *task,
> bool (*match)(struct callback_head *, void *data), void *data);
> struct callback_head *task_work_cancel_func(struct task_struct *,
> task_work_func_t);
> bool task_work_cancel(struct task_struct *task, struct callback_head *cb);
> +bool task_work_has_func(struct task_struct *task, task_work_func_t func);
> void task_work_run(void);
>
> static inline void exit_task_work(struct task_struct *task)
> diff --git a/kernel/task_work.c b/kernel/task_work.c
> index 0f7519f8e7c9..f83d1528e0bc 100644
> --- a/kernel/task_work.c
> +++ b/kernel/task_work.c
> @@ -189,6 +189,20 @@ bool task_work_cancel(struct task_struct *task, struct
> callback_head *cb)
> return ret == cb;
> }
>
> +bool task_work_has_func(struct task_struct *task, task_work_func_t func)
> +{
> + struct callback_head *work;
> +
> + if (!task_work_pending(task))
> + return false;
> + guard(raw_spinlock_irqsave)(&task->pi_lock);
> + for (work = READ_ONCE(task->task_works); work; work =
> READ_ONCE(work->next)) {
> + if (work->func == func)
> + return true;
> + }
> + return false;
> +}
> +
> /**
> * task_work_run - execute the works added by task_work_add()
> *
This thing is quite terrible. And AFAICT the only purpose is to
determine if said task already has said function enqueued. Why not add a
single bit to struct task_struct for this? I'm sure we have a spare bit
somewhere.
> +/* replace the current task's stale label on syscall return */
> +void aa_schedule_stale_label_replacement(void)
> +{
> + struct callback_head *tw;
> +
> + if (task_work_has_func(current, aa_replace_stale_label_tw_func))
> + return;
> + tw = kmalloc_obj(struct callback_head);
> + if (!tw)
> + return;
> + init_task_work(tw, aa_replace_stale_label_tw_func);
> + if (task_work_add(current, tw, TWA_RESUME))
> + kfree(tw);
> +}
