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Subject[PATCH 3.11 197/233] mm: don't lose the SOFT_DIRTY flag on mprotect
Date
3.11.10.4 -stable review patch.  If anyone has any objections, please let me know.

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

From: Andrey Vagin <avagin@openvz.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@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
arch/x86/include/asm/pgtable_types.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index f4843e0..4e700b1 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -118,7 +118,8 @@

/* 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)
--
1.8.3.2


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