[PATCH 4.4 025/163] arm64: Honour !PTE_WRITE in set_pte_at() for kernel mappings

Greg Kroah-Hartman
2016-05-03T01:48:41Z

From: Catalin Marinas <catalin.marinas@arm.com>

commit ac15bd63bbb24238f763ec5b24ee175ec301e8cd upstream.

Currently, set_pte_at() only checks the software PTE_WRITE bit for user
mappings when it sets or clears the hardware PTE_RDONLY accordingly. The
kernel ptes are written directly without any modification, relying
solely on the protection bits in macros like PAGE_KERNEL. However,
modifying kernel pte attributes via pte_wrprotect() would be ignored by
set_pte_at(). Since pte_wrprotect() does not set PTE_RDONLY (it only
clears PTE_WRITE), the new permission is not taken into account.

This patch changes set_pte_at() to adjust the read-only permission for
kernel ptes as well. As a side effect, existing PROT_* definitions used
for kernel ioremap*() need to include PTE_DIRTY | PTE_WRITE.

(additionally, white space fix for PTE_KERNEL_ROX)

Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/include/asm/pgtable.h | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)

--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -69,11 +69,11 @@ extern void __pgd_error(const char *file
#define PROT_DEFAULT (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
#define PROT_SECT_DEFAULT (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)

-#define PROT_DEVICE_nGnRnE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_ATTRINDX(MT_DEVICE_nGnRnE))
-#define PROT_DEVICE_nGnRE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_ATTRINDX(MT_DEVICE_nGnRE))
-#define PROT_NORMAL_NC (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_ATTRINDX(MT_NORMAL_NC))
-#define PROT_NORMAL_WT (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_ATTRINDX(MT_NORMAL_WT))
-#define PROT_NORMAL (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_ATTRINDX(MT_NORMAL))
+#define PROT_DEVICE_nGnRnE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_DEVICE_nGnRnE))
+#define PROT_DEVICE_nGnRE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_DEVICE_nGnRE))
+#define PROT_NORMAL_NC (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_NC))
+#define PROT_NORMAL_WT (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_WT))
+#define PROT_NORMAL (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL))

#define PROT_SECT_DEVICE_nGnRE (PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_DEVICE_nGnRE))
#define PROT_SECT_NORMAL (PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_NORMAL))
@@ -83,7 +83,7 @@ extern void __pgd_error(const char *file

#define PAGE_KERNEL __pgprot(_PAGE_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE)
#define PAGE_KERNEL_RO __pgprot(_PAGE_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_RDONLY)
-#define PAGE_KERNEL_ROX __pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_RDONLY)
+#define PAGE_KERNEL_ROX __pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_RDONLY)
#define PAGE_KERNEL_EXEC __pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE)
#define PAGE_KERNEL_EXEC_CONT __pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_CONT)

@@ -155,6 +155,7 @@ extern struct page *empty_zero_page;
#define pte_write(pte) (!!(pte_val(pte) & PTE_WRITE))
#define pte_exec(pte) (!(pte_val(pte) & PTE_UXN))
#define pte_cont(pte) (!!(pte_val(pte) & PTE_CONT))
+#define pte_user(pte) (!!(pte_val(pte) & PTE_USER))

#ifdef CONFIG_ARM64_HW_AFDBM
#define pte_hw_dirty(pte) (pte_write(pte) && !(pte_val(pte) & PTE_RDONLY))
@@ -165,8 +166,6 @@ extern struct page *empty_zero_page;
#define pte_dirty(pte) (pte_sw_dirty(pte) || pte_hw_dirty(pte))

#define pte_valid(pte) (!!(pte_val(pte) & PTE_VALID))
-#define pte_valid_user(pte) \
- ((pte_val(pte) & (PTE_VALID | PTE_USER)) == (PTE_VALID | PTE_USER))
#define pte_valid_not_user(pte) \
((pte_val(pte) & (PTE_VALID | PTE_USER)) == PTE_VALID)

@@ -264,13 +263,13 @@ 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_valid_user(pte)) {
- if (!pte_special(pte) && pte_exec(pte))
- __sync_icache_dcache(pte, addr);
+ if (pte_valid(pte)) {
if (pte_sw_dirty(pte) && pte_write(pte))
pte_val(pte) &= ~PTE_RDONLY;
else
pte_val(pte) |= PTE_RDONLY;
+ if (pte_user(pte) && pte_exec(pte) && !pte_special(pte))
+ __sync_icache_dcache(pte, addr);
}

/*