On Fri, Nov 6, 2015 at 3:41 PM, Laura Abbott <labbott@xxxxxxxxxx> wrote: > On 11/06/2015 12:46 PM, Russell King - ARM Linux wrote: >> >> On Fri, Nov 06, 2015 at 10:44:32AM -0800, Laura Abbott wrote: >>> >>> with my test patch. I think setting both current->active_mm and &init_mm >>> is sufficient. Maybe explicitly setting swapper_pg_dir would be cleaner? >> >> >> Please, stop thinking like this. If you're trying to change the kernel >> section mappings after threads have been spawned, you need to change >> them for _all_ threads, which means you need to change them for every >> page table that's in existence at that time - you can't do just one >> table and hope everyone updates, it doesn't work like that. >> > > That's a bad assumption assumption on my part based on what I was > observing. At the time of mark_rodata_ro, the only threads present > are kernel threads which aren't going to have task->mm. Only the > running thread is going to have active_mm. None of those are init_mm. > To be complete we need: > > - Update every task->mm for every thread in every process > - Update current->active_mm > - Update &init_mm explicitly > > All this would need to be done under stop_machine as well. Does that cover > everything or am I still off? I still think we need to find an earlier place to do this. :( -Kees -- Kees Cook Chrome OS Security -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>