Commit a8f60d1f authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Martin Schwidefsky

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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent c08e611b
...@@ -1051,6 +1051,8 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, ...@@ -1051,6 +1051,8 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
{ {
if (!MACHINE_HAS_NX) if (!MACHINE_HAS_NX)
pte_val(entry) &= ~_PAGE_NOEXEC; pte_val(entry) &= ~_PAGE_NOEXEC;
if (pte_present(entry))
pte_val(entry) &= ~_PAGE_UNUSED;
if (mm_has_pgste(mm)) if (mm_has_pgste(mm))
ptep_set_pte_at(mm, addr, ptep, entry); ptep_set_pte_at(mm, addr, ptep, entry);
else else
......
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