ARM: fix get_user_pages_fast

Ensure that get_user_pages_fast() is not able to access memory which
has been mapped with PROT_NONE.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index 1c462381c225eea31346ec4f19145e3fd449caab..150ece66ddf34506cf8d36963c2461a8188ebe91 100644 (file)
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -232,6 +232,18 @@ static inline pte_t *pmd_page_vaddr(pmd_t pmd)
 #define pte_valid_user(pte)    \
        (pte_valid(pte) && pte_isset((pte), L_PTE_USER) && pte_young(pte))
 
+static inline bool pte_access_permitted(pte_t pte, bool write)
+{
+       pteval_t mask = L_PTE_PRESENT | L_PTE_USER;
+       pteval_t needed = mask;
+
+       if (write)
+               mask |= L_PTE_RDONLY;
+
+       return (pte_val(pte) & mask) == needed;
+}
+#define pte_access_permitted pte_access_permitted
+
 #if __LINUX_ARM_ARCH__ < 6
 static inline void __sync_icache_dcache(pte_t pteval)
 {