Messages in this thread | | | Date | Thu, 6 Jul 2017 08:47:34 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH] mm: mm, mmap: do not blow on PROT_NONE MAP_FIXED holes in the stack |
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On Wed 05-07-17 14:18:49, Andrew Morton wrote: > On Wed, 5 Jul 2017 20:28:49 +0200 Michal Hocko <mhocko@kernel.org> wrote: > > > "mm: enlarge stack guard gap" has introduced a regression in some rust > > and Java environments which are trying to implement their own stack > > guard page. They are punching a new MAP_FIXED mapping inside the > > existing stack Vma. > > > > This will confuse expand_{downwards,upwards} into thinking that the stack > > expansion would in fact get us too close to an existing non-stack vma > > which is a correct behavior wrt. safety. It is a real regression on > > the other hand. Let's work around the problem by considering PROT_NONE > > mapping as a part of the stack. This is a gros hack but overflowing to > > such a mapping would trap anyway an we only can hope that usespace > > knows what it is doing and handle it propely. > > > > Fixes: d4d2d35e6ef9 ("mm: larger stack guard gap, between vmas") > > That should be 1be7107fbe18, yes?
yes. d4d2d35e6ef9 was a cherry-pick into the mmotm git tree. Sorry about that.
> > Debugged-by: Vlastimil Babka <vbabka@suse.cz> > > Signed-off-by: Michal Hocko <mhocko@suse.com>
-- Michal Hocko SUSE Labs
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