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authorHugh Dickins <hughd@google.com>2016-07-14 12:07:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-07-15 14:54:27 +0900
commit5a49973d7143ebbabd76e1dcd69ee42e349bb7b9 (patch)
treee1dc7cdb669b7fecf3a331b7a64183b1f24c65c5 /mm/memory.c
parent55bda43bb26d2c11eeedac742eff87a8ac34c106 (diff)
downloadop-kernel-dev-5a49973d7143ebbabd76e1dcd69ee42e349bb7b9.zip
op-kernel-dev-5a49973d7143ebbabd76e1dcd69ee42e349bb7b9.tar.gz
mm: thp: refix false positive BUG in page_move_anon_rmap()
The VM_BUG_ON_PAGE in page_move_anon_rmap() is more trouble than it's worth: the syzkaller fuzzer hit it again. It's still wrong for some THP cases, because linear_page_index() was never intended to apply to addresses before the start of a vma. That's easily fixed with a signed long cast inside linear_page_index(); and Dmitry has tested such a patch, to verify the false positive. But why extend linear_page_index() just for this case? when the avoidance in page_move_anon_rmap() has already grown ugly, and there's no reason for the check at all (nothing else there is using address or index). Remove address arg from page_move_anon_rmap(), remove VM_BUG_ON_PAGE, remove CONFIG_DEBUG_VM PageTransHuge adjustment. And one more thing: should the compound_head(page) be done inside or outside page_move_anon_rmap()? It's usually pushed down to the lowest level nowadays (and mm/memory.c shows no other explicit use of it), so I think it's better done in page_move_anon_rmap() than by caller. Fixes: 0798d3c022dc ("mm: thp: avoid false positive VM_BUG_ON_PAGE in page_move_anon_rmap()") Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1607120444540.12528@eggly.anvils Signed-off-by: Hugh Dickins <hughd@google.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Mika Westerberg <mika.westerberg@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: <stable@vger.kernel.org> [4.5+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memory.c')
-rw-r--r--mm/memory.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/memory.c b/mm/memory.c
index cd1f29e..9e04681 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2399,8 +2399,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
* Protected against the rmap code by
* the page lock.
*/
- page_move_anon_rmap(compound_head(old_page),
- vma, address);
+ page_move_anon_rmap(old_page, vma);
}
unlock_page(old_page);
return wp_page_reuse(mm, vma, address, page_table, ptl,
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