| From 7a6702934290446bcfa4a34e55af96fc9db61aa1 Mon Sep 17 00:00:00 2001 |
| From: Hugh Dickins <hughd@google.com> |
| Date: Tue, 20 Jun 2017 02:10:44 -0700 |
| Subject: [PATCH] mm: fix new crash in unmapped_area_topdown() |
| |
| 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 <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> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/mm/mmap.c b/mm/mmap.c |
| index 7656743eed2f..5680e300e279 100644 |
| --- a/mm/mmap.c |
| +++ b/mm/mmap.c |
| @@ -1660,7 +1660,8 @@ 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 */ |
| @@ -1763,7 +1764,8 @@ 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 */ |
| -- |
| 2.12.0 |
| |
