linux-kernel - [PATCH 3.12 018/107] mm: dont lose the SOFT

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Message-Id: <20140211184748.722306161@linuxfoundation.org>
Date:	Tue, 11 Feb 2014 11:04:44 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Andrey Vagin <avagin@...nvz.org>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Borislav Petkov <bp@...e.de>,
	Wen Congyang <wency@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.12 018/107] mm: dont lose the SOFT_DIRTY flag on mprotect

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrey Vagin <avagin@...nvz.org>

commit 24f91eba18bbfdb27e71a1aae5b3a61b67fcd091 upstream.

The SOFT_DIRTY bit shows that the content of memory was changed after a
defined point in the past.  mprotect() doesn't change the content of
memory, so it must not change the SOFT_DIRTY bit.

This bug causes a malfunction: on the first iteration all pages are
dumped.  On other iterations only pages with the SOFT_DIRTY bit are
dumped.  So if the SOFT_DIRTY bit is cleared from a page by mistake, the
page is not dumped and its content will be restored incorrectly.

This patch does nothing with _PAGE_SWP_SOFT_DIRTY, becase pte_modify()
is called only for present pages.

Fixes commit 0f8975ec4db2 ("mm: soft-dirty bits for user memory changes
tracking").

Signed-off-by: Andrey Vagin <avagin@...nvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@...nvz.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Pavel Emelyanov <xemul@...allels.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: Wen Congyang <wency@...fujitsu.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/include/asm/pgtable_types.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -121,7 +121,8 @@

 /* Set of bits not changed in pte_modify */
 #define _PAGE_CHG_MASK	(PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT |		\
-			 _PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY)
+			 _PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY |	\
+			 _PAGE_SOFT_DIRTY)
 #define _HPAGE_CHG_MASK (_PAGE_CHG_MASK | _PAGE_PSE)

 #define _PAGE_CACHE_MASK	(_PAGE_PCD | _PAGE_PWT)

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