Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 09/21] s390/mm: fix CMMA vs KSM vs others | Date | Tue, 25 Apr 2017 16:09:04 +0100 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Christian Borntraeger <borntraeger@de.ibm.com>
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 <borntraeger@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- arch/s390/include/asm/pgtable.h | 2 ++ 1 file changed, 2 insertions(+)
--- 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_stru 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
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