From a8f60d1fadf7b8b54449fcc9d6b15248917478ba Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Sun, 9 Apr 2017 22:09:38 +0200 Subject: [PATCH] s390/mm: fix CMMA vs KSM vs others On heavy paging with KSM I see guest data corruption. Turns out that KSM will add pages to its tree, where the mapping return true for pte_unused (or might become as such later). KSM will unmap such pages and reinstantiate with different attributes (e.g. write protected or special, e.g. in replace_page or write_protect_page)). This uncovered a bug in our pagetable handling: We must remove the unused flag as soon as an entry becomes present again. Cc: stable@vger.kernel.org Signed-of-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky --- arch/s390/include/asm/pgtable.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index 93e37b12e8823..ecec682bb5166 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -1051,6 +1051,8 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, { if (!MACHINE_HAS_NX) pte_val(entry) &= ~_PAGE_NOEXEC; + if (pte_present(entry)) + pte_val(entry) &= ~_PAGE_UNUSED; if (mm_has_pgste(mm)) ptep_set_pte_at(mm, addr, ptep, entry); else