On Tue 04-07-17 12:36:11, Ben Hutchings wrote: > On Tue, 2017-07-04 at 12:42 +0200, Michal Hocko wrote: > > On Tue 04-07-17 11:47:28, Willy Tarreau wrote: > > > On Tue, Jul 04, 2017 at 11:35:38AM +0200, Michal Hocko wrote: > [...] > > > But wouldn't this completely disable the check in case such a guard page > > > is installed, and possibly continue to allow the collision when the stack > > > allocation is large enough to skip this guard page ? > > > > Yes and but a PROT_NONE would fault and as the changelog says, we _hope_ > > that userspace does the right thing. > > It may well not be large enough, because of the same wrong assumptions > that resulted in the kernel's guard page not being large enough. We > should count it as part of the guard gap but not a substitute.
yes, you are right of course. But isn't this a bug on their side considering they are managing their _own_ stack gap? Our stack gap management is a best effort thing and two such approaches competing will always lead to weird cornercases. That was my assumption when saying that I am not sure this is really _worth_ it. We should definitely try to workaround clashes but that's about it. If others think that we should do everything to prevent even those issues I will not oppose of course. It just adds more cycles to something that is a weird case already. [...] > This *doesn't* fix the LibreOffice regression on i386. Are there any details about this regression? -- Michal Hocko SUSE Labs
