On 8/6/26 00:32, Peter Zijlstra wrote:
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.
single bit wouldn't work generically to represent the different functions that could be enqueued but we could stick a flag in the apparmor task security blob, so we could just check if apparmor has enqueued its function. The trade-off is you don't get an admittedly ugly generic fn that someone else could use.
+/* 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); +}
