54 lines
2.1 KiB
Diff
54 lines
2.1 KiB
Diff
From patchwork Tue Jun 20 09:10:44 2017
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Content-Type: text/plain; charset="utf-8"
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MIME-Version: 1.0
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Content-Transfer-Encoding: 7bit
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Subject: mm: fix new crash in unmapped_area_topdown()
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From: Hugh Dickins <hughd@google.com>
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X-Patchwork-Id: 9798991
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Message-Id: <alpine.LSU.2.11.1706200206210.10925@eggly.anvils>
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To: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Dave Jones <davej@codemonkey.org.uk>, Oleg Nesterov <oleg@redhat.com>,
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Michal Hocko <mhocko@suse.com>, linux-kernel@vger.kernel.org,
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linux-mm@kvack.org
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Date: Tue, 20 Jun 2017 02:10:44 -0700 (PDT)
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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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---
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mm/mmap.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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--- 4.12-rc6/mm/mmap.c 2017-06-19 09:06:10.035407505 -0700
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+++ linux/mm/mmap.c 2017-06-19 21:09:28.616707311 -0700
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@@ -1817,7 +1817,8 @@ unsigned long unmapped_area(struct vm_un
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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(stru
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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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