mm: fix new crash in unmapped_area_topdown()
authorHugh Dickins <hughd@google.com>
Tue, 20 Jun 2017 09:10:44 +0000 (02:10 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 21 Jun 2017 17:56:11 +0000 (10:56 -0700)
commitf4cb767d76cf7ee72f97dd76f6cfa6c76a5edc89
tree425524affe25e84c5d1efbf1c5785f3c2c2cce33
parent9705596d08ac87c18aee32cc97f2783b7d14624e
mm: fix new crash in unmapped_area_topdown()

Trinity gets kernel BUG at mm/mmap.c:1963! in about 3 minutes of
mmap testing.  That's the VM_BUG_ON(gap_end < gap_start) at the
end of unmapped_area_topdown().  Linus points out how MAP_FIXED
(which does not have to respect our stack guard gap intentions)
could result in gap_end below gap_start there.  Fix that, and
the similar case in its alternative, unmapped_area().

Cc: stable@vger.kernel.org
Fixes: 1be7107fbe18 ("mm: larger stack guard gap, between vmas")
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Debugged-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/mmap.c