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authorHugh Dickins <hughd@google.com>2017-06-20 02:10:44 -0700
committerWilly Tarreau <w@1wt.eu>2017-06-22 15:21:11 +0200
commit28ebf89579a055259280252f68f6c26d986e3ce3 (patch)
treee27474b59591a759b01a3849c3f0c540f8376c77
parent1ad9a25dd06fda9bdc27875e1cedb8277accb212 (diff)
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: Willy Tarreau <w@1wt.eu>
-rw-r--r--mm/mmap.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 385a5d96942b..873dc9412163 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 */