From: Christian Borntraeger Date: Sun, 9 Apr 2017 20:09:38 +0000 (+0200) Subject: s390/mm: fix CMMA vs KSM vs others X-Git-Tag: v4.10.13~14 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0cb760dfc75b16740dc47862806f8bb254f07b8e;p=thirdparty%2Fkernel%2Fstable.git s390/mm: fix CMMA vs KSM vs others commit a8f60d1fadf7b8b54449fcc9d6b15248917478ba upstream. 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. Signed-of-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index 0362cd5fa187c..0cea7026e4ffd 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -1029,6 +1029,8 @@ int get_guest_storage_key(struct mm_struct *mm, unsigned long addr, static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t entry) { + if (pte_present(entry)) + pte_val(entry) &= ~_PAGE_UNUSED; if (mm_has_pgste(mm)) ptep_set_pte_at(mm, addr, ptep, entry); else