On Wed, Dec 08, 2021 at 02:25:25PM -0600, Eric W. Biederman wrote: > The beginning of do_exit has become cluttered and difficult to read as > it is filled with checks to handle things that can only happen when > the kernel is operating improperly. > > Now that we have a dedicated function for cleaning up a task when the > kernel is operating improperly move the checks there. Umm... I would probably take profile_task_exit() crap out before that point. 1) the damn thing is dead - nothing registers notifiers there 2) blocking_notifier_call_chain() is not a nice thing to do on oops... I'll post a patch ripping the dead parts of kernel/profile.c out tomorrow morning (there's also profile_handoff_task(), equally useless these days and complicating things for __put_task_struct()). > - /* > - * If do_exit is called because this processes oopsed, it's possible > - * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before > - * continuing. Amongst other possible reasons, this is to prevent > - * mm_release()->clear_child_tid() from writing to a user-controlled > - * kernel address. > - */ > - force_uaccess_begin(); Are you sure about that one? It shouldn't matter, but... it's a potential change for do_exit() from a kernel thread. As it is, we have that force_uaccess_begin() for exiting threads and for kernel ones it's not a no-op. I'm not concerned about attempted userland access after that point for those, obviously, but I'm not sure you won't step into something subtle here. I would prefer to split that particular change off into a separate commit...
