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Fix false positive VM_BUG() in page_add_file_rmap (rhbz 1365686)

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Laura Abbott 2016-08-10 13:00:33 -07:00
parent 23689dd81c
commit 2acb794259
2 changed files with 50 additions and 0 deletions
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44
0001-mm-rmap-fix-false-positive-VM_BUG-in-page_add_file_r.patch Normal file
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@ -0,0 +1,44 @@
From 6abb0cfdc1f6a42367a20ac2baf4099fc8af08b5 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Wed, 10 Aug 2016 09:54:30 -0700
Subject: [PATCH] mm, rmap: fix false positive VM_BUG() in page_add_file_rmap()
PageTransCompound() doesn't distinguish THP from from any other type of
compound pages. This can lead to false-positive VM_BUG_ON() in
page_add_file_rmap() if called on compound page from a driver[1].
I think we can exclude such cases by checking if the page belong to a
mapping.
The VM_BUG_ON_PAGE() is downgraded to VM_WARN_ON_ONCE(). This path
should not cause any harm to non-THP page, but good to know if we step
on anything else.
[1]
http://lkml.kernel.org/r/c711e067-0bff-a6cb-3c37-04dfe77d2db1@redhat.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Laura Abbott <labbott@redhat.com>
---
mm/rmap.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 709bc83..d4f5606 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1284,8 +1284,9 @@ void page_add_file_rmap(struct page *page, bool compound)
VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
__inc_node_page_state(page, NR_SHMEM_PMDMAPPED);
} else {
- if (PageTransCompound(page)) {
- VM_BUG_ON_PAGE(!PageLocked(page), page);
+ if (PageTransCompound(page) && page_mapping(page)) {
+ VM_WARN_ON_ONCE(!PageLocked(page));
+
SetPageDoubleMap(compound_head(page));
if (PageMlocked(page))
clear_page_mlock(compound_head(page));
--
2.7.4

6
kernel.spec
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@ -601,6 +601,9 @@ Patch665: netfilter-x_tables-deal-with-bogus-nextoffset-values.patch
# https://lists.fedoraproject.org/archives/list/kernel@lists.fedoraproject.org/message/A4YCP7OGMX6JLFT5V44H57GOMAQLC3M4/
Patch839: drm-i915-Acquire-audio-powerwell-for-HD-Audio-regist.patch
#rhbz 1365686
Patch840: 0001-mm-rmap-fix-false-positive-VM_BUG-in-page_add_file_r.patch
# END OF PATCH DEFINITIONS
%endif
@ -2135,6 +2138,9 @@ fi
#
#
%changelog
* Wed Aug 10 2016 Laura Abbott <labbott@fedoraproject.org>
- Fix false positive VM_BUG() in page_add_file_rmap (rhbz 1365686)
* Wed Aug 10 2016 Justin M. Forbes <jforbes@fedoraproject.org> - 4.8.0-0.rc1.git2.1
- Linux v4.8-rc1-53-ga0cba21