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author | Michal Hocko <mhocko@suse.com> | 2017-07-10 15:49:51 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-07-10 16:32:33 -0700 |
commit | 561b5e0709e4a248c67d024d4d94b6e31e3edf2f (patch) | |
tree | 8a5424e03ba4704bb57309eeaeb85fe10a10a598 /mm/shmem.c | |
parent | bb01b64cfab7c22f3848cb73dc0c2b46b8d38499 (diff) | |
download | op-kernel-dev-561b5e0709e4a248c67d024d4d94b6e31e3edf2f.zip op-kernel-dev-561b5e0709e4a248c67d024d4d94b6e31e3edf2f.tar.gz |
mm/mmap.c: do not blow on PROT_NONE MAP_FIXED holes in the stack
Commit 1be7107fbe18 ("mm: larger stack guard gap, between vmas") 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: 1be7107fbe18 ("mm: larger stack guard gap, between vmas")
Link: http://lkml.kernel.org/r/20170705182849.GA18027@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Debugged-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
0 files changed, 0 insertions, 0 deletions