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

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Date:   Tue, 26 Jun 2018 17:22:29 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv4 02/18] mm/ksm: Do not merge pages with different KeyIDs

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@...ux.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