On Fri, 25 Oct 2019 09:33:26 +0200 Vlastimil Babka <vbabka@xxxxxxx> wrote: > On 10/25/19 9:26 AM, Michal Hocko wrote: > > From: Michal Hocko <mhocko@xxxxxxxx> > > > > /proc/pagetypeinfo is a debugging tool to examine internal page > > allocator state wrt to fragmentation. It is not very useful for > > any other use so normal users really do not need to read this file. > > > > Waiman Long has noticed that reading this file can have negative side > > effects because zone->lock is necessary for gathering data and that > > a) interferes with the page allocator and its users and b) can lead to > > hard lockups on large machines which have very long free_list. > > > > Reduce both issues by simply not exporting the file to regular users. > > > > Reported-by: Waiman Long <longman@xxxxxxxxxx> > > Cc: stable > > Cc: <stable@xxxxxxxxxxxxxxx> As we don't really know how much damage this will cause, it would be nice to let it bake in mainline for a month or three before committing it to the -stable trees. But we don't have a process for that, apart from remembering to poke Greg at a suitable date. Oh well. I guess that if someone is truly harmed by this change, they can just chmod /proc/pagetypeinfo back to 0444.
