ARM: 7487/1: mm: avoid setting nG bit for user mappings that aren't present
Swap entries are encoding in ptes such that !pte_present(pte) and
pte_file(pte). The remaining bits of the descriptor are used to identify
the swapfile and offset within it to the swap entry.
When writing such a pte for a user virtual address, set_pte_at
unconditionally sets the nG bit, which (in the case of LPAE) will
corrupt the swapfile offset and lead to a BUG:
[ 140.494067] swap_free: Unused swap offset entry 000763b4
[ 140.509989] BUG: Bad page map in process rs:main Q:Reg pte:0ec76800 pmd:8f92e003
This patch fixes the problem by only setting the nG bit for user
mappings that are actually present.
Cc: <stable@vger.kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index f66626d..d88f9f0 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -195,25 +195,6 @@
#define pte_clear(mm,addr,ptep) set_pte_ext(ptep, __pte(0), 0)
-#if __LINUX_ARM_ARCH__ < 6
-static inline void __sync_icache_dcache(pte_t pteval)
-{
-}
-#else
-extern void __sync_icache_dcache(pte_t pteval);
-#endif
-
-static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
- pte_t *ptep, pte_t pteval)
-{
- if (addr >= TASK_SIZE)
- set_pte_ext(ptep, pteval, 0);
- else {
- __sync_icache_dcache(pteval);
- set_pte_ext(ptep, pteval, PTE_EXT_NG);
- }
-}
-
#define pte_none(pte) (!pte_val(pte))
#define pte_present(pte) (pte_val(pte) & L_PTE_PRESENT)
#define pte_write(pte) (!(pte_val(pte) & L_PTE_RDONLY))
@@ -226,6 +207,27 @@
((pte_val(pte) & (L_PTE_PRESENT | L_PTE_USER)) == \
(L_PTE_PRESENT | L_PTE_USER))
+#if __LINUX_ARM_ARCH__ < 6
+static inline void __sync_icache_dcache(pte_t pteval)
+{
+}
+#else
+extern void __sync_icache_dcache(pte_t pteval);
+#endif
+
+static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, pte_t pteval)
+{
+ unsigned long ext = 0;
+
+ if (addr < TASK_SIZE && pte_present_user(pteval)) {
+ __sync_icache_dcache(pteval);
+ ext |= PTE_EXT_NG;
+ }
+
+ set_pte_ext(ptep, pteval, ext);
+}
+
#define PTE_BIT_FUNC(fn,op) \
static inline pte_t pte_##fn(pte_t pte) { pte_val(pte) op; return pte; }
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 7745854..40ca11e 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -231,8 +231,6 @@
struct page *page;
struct address_space *mapping;
- if (!pte_present_user(pteval))
- return;
if (cache_is_vipt_nonaliasing() && !pte_exec(pteval))
/* only flush non-aliasing VIPT caches for exec mappings */
return;