Hello. On Thu, Jun 09, 2022 at 11:49:38AM +0800, 史思远 <shisiyuan19870131@xxxxxxxxx> wrote: > The process is like above photo, thread 2 exits > between cgroup_migrate_prepare_dst() and cgroup_migrate_execute(). > Then the refcount of csetX turns to be 0 here, and UAF appears when thread1 > migrating. > Thread2 exits asynchronously, can rwsem prevent it? See the bailout in cgroup_migrate_add_task(): if (task->flags & PF_EXITING) return; And cgroup_threadgroup_change_begin(tsk) in exit_signals(). > The purpose of my patch is to keep csetX's refcount still 1 after thread2 > exits, and make sure thread1 migrating successfully. Why is not src_cset==dst_cset in cgroup_migrate_prepare_dst() not sufficient? Still, can this be reproduced in real world or is your reasoning based on theory only? Thanks, Michal
