4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
commit 58ceeb6bec86d9140f9d91d71a710e963523d063 upstream.
Both MADV_DONTNEED and MADV_FREE handled with down_read(mmap_sem).
It's critical to not clear pmd intermittently while handling MADV_FREE
to avoid race with MADV_DONTNEED:
CPU0: CPU1:
madvise_free_huge_pmd()
pmdp_huge_get_and_clear_full()
madvise_dontneed()
zap_pmd_range()
pmd_trans_huge(*pmd) == 0 (without ptl)
// skip the pmd
set_pmd_at();
// pmd is re-established
It results in MADV_DONTNEED skipping the pmd, leaving it not cleared.
It violates MADV_DONTNEED interface and can result is userspace
misbehaviour.
Basically it's the same race as with numa balancing in
change_huge_pmd(), but a bit simpler to mitigate: we don't need to
preserve dirty/young flags here due to MADV_FREE functionality.
[kirill.shute...@linux.intel.com: Urgh... Power is special again]
Link:
http://lkml.kernel.org/r/20170303102636.bhd2zhtpds4mt...@black.fi.intel.com
Link:
http://lkml.kernel.org/r/20170302151034.27829-4-kirill.shute...@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Acked-by: Minchan Kim <minc...@kernel.org>
Cc: Minchan Kim <minc...@kernel.org>
Cc: Andrea Arcangeli <aarca...@redhat.com>
Cc: Hillf Danton <hillf...@alibaba-inc.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
mm/huge_memory.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1380,8 +1380,7 @@ bool madvise_free_huge_pmd(struct mmu_ga
deactivate_page(page);
if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
- orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
- tlb->fullmm);
+ pmdp_invalidate(vma, addr, pmd);
orig_pmd = pmd_mkold(orig_pmd);
orig_pmd = pmd_mkclean(orig_pmd);
