From 1ee5e87f86deca84fdcb7c71bb8368cacc4c24e3 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Wed, 25 Oct 2017 11:04:14 +0100
Subject: [PATCH] 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>
---
arch/arm/include/asm/pgtable.h | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index 1c462381c225ee..150ece66ddf345 100644
--- 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)
{
--
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