From 880bd724f76f26f712968fdf4917174b16540a4d Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 20 Jun 2017 02:10:44 -0700 Subject: [PATCH 2/3] [SEC][Backport] mm: fix new crash in unmapped_area_topdown() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit f4cb767d76cf7ee72f97dd76f6cfa6c76a5edc89 upstream. 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 Debugged-by: Linus Torvalds Signed-off-by: Hugh Dickins Acked-by: Michal Hocko Signed-off-by: Linus Torvalds Signed-off-by: Willy Tarreau Signed-off-by: Jan-Simon Möller --- mm/mmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index cbdac38..4a113e3 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1700,7 +1700,8 @@ check_current: /* Check if current node has a suitable gap */ if (gap_start > high_limit) return -ENOMEM; - if (gap_end >= low_limit && gap_end - gap_start >= length) + if (gap_end >= low_limit && + gap_end > gap_start && gap_end - gap_start >= length) goto found; /* Visit right subtree if it looks promising */ @@ -1803,7 +1804,8 @@ check_current: gap_end = vm_start_gap(vma); if (gap_end < low_limit) return -ENOMEM; - if (gap_start <= high_limit && gap_end - gap_start >= length) + if (gap_start <= high_limit && + gap_end > gap_start && gap_end - gap_start >= length) goto found; /* Visit left subtree if it looks promising */ -- 2.1.4