[ 04/33] arm64: mm: only wrprotect clean ptes if they are present

Greg Kroah-Hartman
2013-01-19T01:36:51Z

From: Will Deacon <will.deacon@arm.com>

commit 02522463c84748b3b8ad770f9424bcfa70a5b4c4 upstream.

Marking non-present ptes as read-only can corrupt file ptes, breaking
things like swap and file mappings.

This patch ensures that we only manipulate user pte bits when the pte
is marked present.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/include/asm/pgtable.h | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -132,9 +132,8 @@ extern struct page *empty_zero_page;
#define pte_write(pte) (!(pte_val(pte) & PTE_RDONLY))
#define pte_exec(pte) (!(pte_val(pte) & PTE_UXN))

-#define pte_present_exec_user(pte) \
- ((pte_val(pte) & (PTE_VALID | PTE_USER | PTE_UXN)) == \
- (PTE_VALID | PTE_USER))
+#define pte_present_user(pte) \
+ ((pte_val(pte) & (PTE_VALID | PTE_USER)) == (PTE_VALID | PTE_USER))

#define PTE_BIT_FUNC(fn,op) \
static inline pte_t pte_##fn(pte_t pte) { pte_val(pte) op; return pte; }
@@ -157,10 +156,13 @@ extern void __sync_icache_dcache(pte_t p
static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pte)
{
- if (pte_present_exec_user(pte))
- __sync_icache_dcache(pte, addr);
- if (!pte_dirty(pte))
- pte = pte_wrprotect(pte);
+ if (pte_present_user(pte)) {
+ if (pte_exec(pte))
+ __sync_icache_dcache(pte, addr);
+ if (!pte_dirty(pte))
+ pte = pte_wrprotect(pte);
+ }
+
set_pte(ptep, pte);
}