From: Andrey Vagin <avagin@xxxxxxxxxx>
Subject: mm: don't lose the SOFT_DIRTY flag on mprotect
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 0f8975ec4db2 ("mm: soft-dirty bits for user memory changes
tracking").
Signed-off-by: Andrey Vagin <avagin@xxxxxxxxxx>
Acked-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Wen Congyang <wency@xxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/pgtable_types.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff -puN arch/x86/include/asm/pgtable_types.h~mm-dont-lose-the-soft_dirty-flag-on-mprotect arch/x86/include/asm/pgtable_types.h
--- a/arch/x86/include/asm/pgtable_types.h~mm-dont-lose-the-soft_dirty-flag-on-mprotect
+++ a/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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