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48 lines
1.9 KiB
Diff
48 lines
1.9 KiB
Diff
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From f4cb767d76cf7ee72f97dd76f6cfa6c76a5edc89 Mon Sep 17 00:00:00 2001
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From: Hugh Dickins <hughd@google.com>
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Date: Tue, 20 Jun 2017 02:10:44 -0700
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Subject: [PATCH] mm: fix new crash in unmapped_area_topdown()
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Trinity gets kernel BUG at mm/mmap.c:1963! in about 3 minutes of
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mmap testing. That's the VM_BUG_ON(gap_end < gap_start) at the
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end of unmapped_area_topdown(). Linus points out how MAP_FIXED
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(which does not have to respect our stack guard gap intentions)
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could result in gap_end below gap_start there. Fix that, and
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the similar case in its alternative, unmapped_area().
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Cc: stable@vger.kernel.org
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Fixes: 1be7107fbe18 ("mm: larger stack guard gap, between vmas")
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Reported-by: Dave Jones <davej@codemonkey.org.uk>
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Debugged-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Hugh Dickins <hughd@google.com>
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Acked-by: Michal Hocko <mhocko@suse.com>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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mm/mmap.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/mm/mmap.c b/mm/mmap.c
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index 8e07976d5e477..290b77d9a01e0 100644
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--- a/mm/mmap.c
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+++ b/mm/mmap.c
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@@ -1817,7 +1817,8 @@ unsigned long unmapped_area(struct vm_unmapped_area_info *info)
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/* Check if current node has a suitable gap */
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if (gap_start > high_limit)
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return -ENOMEM;
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- if (gap_end >= low_limit && gap_end - gap_start >= length)
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+ if (gap_end >= low_limit &&
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+ gap_end > gap_start && gap_end - gap_start >= length)
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goto found;
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/* Visit right subtree if it looks promising */
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@@ -1920,7 +1921,8 @@ unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
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gap_end = vm_start_gap(vma);
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if (gap_end < low_limit)
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return -ENOMEM;
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- if (gap_start <= high_limit && gap_end - gap_start >= length)
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+ if (gap_start <= high_limit &&
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+ gap_end > gap_start && gap_end - gap_start >= length)
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goto found;
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/* Visit left subtree if it looks promising */
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