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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/rmap.c
parent55bda43bb26d2c11eeedac742eff87a8ac34c106 (diff)
downloadlwn-5a49973d7143ebbabd76e1dcd69ee42e349bb7b9.tar.gz
lwn-5a49973d7143ebbabd76e1dcd69ee42e349bb7b9.zip
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/rmap.c')
-rw-r--r--mm/rmap.c9
1 files changed, 3 insertions, 6 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index e4b713a6ed7e..701b93fea2a0 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1084,23 +1084,20 @@ EXPORT_SYMBOL_GPL(page_mkclean);
* page_move_anon_rmap - move a page to our anon_vma
* @page: the page to move to our anon_vma
* @vma: the vma the page belongs to
- * @address: the user virtual address mapped
*
* When a page belongs exclusively to one process after a COW event,
* that page can be moved into the anon_vma that belongs to just that
* process, so the rmap code will not search the parent or sibling
* processes.
*/
-void page_move_anon_rmap(struct page *page,
- struct vm_area_struct *vma, unsigned long address)
+void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma)
{
struct anon_vma *anon_vma = vma->anon_vma;
+ page = compound_head(page);
+
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_VMA(!anon_vma, vma);
- if (IS_ENABLED(CONFIG_DEBUG_VM) && PageTransHuge(page))
- address &= HPAGE_PMD_MASK;
- VM_BUG_ON_PAGE(page->index != linear_page_index(vma, address), page);
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
/*