On Wed 2022-07-27 10:24:37, Rik van Riel wrote: > v4: address changelog comments by Josh (thank you) > > ---8<--- > When a KLP fails to apply, klp_reverse_transition will clear the > TIF_PATCH_PENDING flag on all tasks, except for newly created tasks > which are not on the task list yet. It actually is not true. klp_reverse_transtion() clears TIF_PATCH_FLAG only temporary when it waits until all processes leave the ftrace handler. It sets TIF_PATCH_FLAG once again for all tasks by calling klp_start_transition(). The difference is important. The WARN_ON_ONCE() in klp_complete_transition() will be printed when fork() copied TIF_PATCH_FLAG before it was set again. Anyway, the important thing is that TIF_PATCH_FLAG and task->patch_state might be incompatible because fork() copies them at different times. klp_copy_process() must make sure that they are in sync. And it must be done under tasklist_lock when the child is added to the global task list. Best Regards, Petr
