On Thu, Sep 23, 2021 at 03:14:48PM +0200, Petr Mladek wrote: > IMHO, this is not safe: > > CPU0 CPU1 > > klp_check_task(A) > if (context_tracking_state_cpu(task_cpu(task)) == CONTEXT_USER) > goto complete; > > clear_tsk_thread_flag(task, TIF_PATCH_PENDING); > > # task switching to kernel space > klp_update_patch_state(A) > if (test_and_clear_tsk_thread_flag(task, TIF_PATCH_PENDING)) > //false > > # calling kernel code with old task->patch_state > > task->patch_state = klp_target_state; > > BANG: CPU0 sets task->patch_state when task A is already running > kernel code on CPU1. Why is that a problem? That is, who actually cares about task->patch_state ? I was under the impression that state was purely for klp itself, to track which task has observed the new state.
