[PATCHv4 02/18] mm/ksm: Do not merge pages with different KeyIDs

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

Pages encrypted with different encryption keys are not subject to KSM
merge. Otherwise it would cross security boundary.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 include/linux/mm.h | 7 +++++++
 mm/ksm.c           | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ebf4bd8bd0bf..406a28cadfcf 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1548,6 +1548,13 @@ static inline int vma_keyid(struct vm_area_struct *vma)
 }
 #endif
 
+#ifndef page_keyid
+static inline int page_keyid(struct page *page)
+{
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_SHMEM
 /*
  * The vma_is_shmem is not inline because it is used only by slow
diff --git a/mm/ksm.c b/mm/ksm.c
index a6d43cf9a982..1bd7b9710e29 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1214,6 +1214,9 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
 	if (!PageAnon(page))
 		goto out;
 
+	if (page_keyid(page) != page_keyid(kpage))
+		goto out;
+
 	/*
 	 * We need the page lock to read a stable PageSwapCache in
 	 * write_protect_page().  We use trylock_page() instead of
-- 
2.18.0