3.2.58-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Will Deacon <will.deacon@xxxxxxx>
commit 26ffd0d43b186b0d5186354da8714a1c2d360df0 upstream.
PROT_NONE mappings apply the page protection attributes defined by _P000
which translate to PAGE_NONE for ARM. These attributes specify an XN,
RDONLY pte that is inaccessible to userspace. However, on kernels
configured without support for domains, such a pte *is* accessible to
the kernel and can be read via get_user, allowing tasks to read
PROT_NONE pages via syscalls such as read/write over a pipe.
This patch introduces a new software pte flag, L_PTE_NONE, that is set
to identify faulting, present entries.
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
[bwh: Backported to 3.2 as dependency of commit b6ccb9803e90
('ARM: 7954/1: mm: remove remaining domain support from ARMv6'):
- Drop 3-level changes
- Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/arch/arm/include/asm/pgtable-2level.h
+++ b/arch/arm/include/asm/pgtable-2level.h
@@ -123,6 +123,7 @@
#define L_PTE_USER (_AT(pteval_t, 1) << 8)
#define L_PTE_XN (_AT(pteval_t, 1) << 9)
#define L_PTE_SHARED (_AT(pteval_t, 1) << 10) /* shared(v6), coherent(xsc3) */
+#define L_PTE_NONE (_AT(pteval_t, 1) << 11)
/*
* These are the memory types, defined to be compatible with
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -74,7 +74,7 @@ extern pgprot_t pgprot_kernel;
#define _MOD_PROT(p, b) __pgprot(pgprot_val(p) | (b))
-#define PAGE_NONE _MOD_PROT(pgprot_user, L_PTE_XN | L_PTE_RDONLY)
+#define PAGE_NONE _MOD_PROT(pgprot_user, L_PTE_XN | L_PTE_RDONLY | L_PTE_NONE)
#define PAGE_SHARED _MOD_PROT(pgprot_user, L_PTE_USER | L_PTE_XN)
#define PAGE_SHARED_EXEC _MOD_PROT(pgprot_user, L_PTE_USER)
#define PAGE_COPY _MOD_PROT(pgprot_user, L_PTE_USER | L_PTE_RDONLY | L_PTE_XN)
@@ -84,7 +84,7 @@ extern pgprot_t pgprot_kernel;
#define PAGE_KERNEL _MOD_PROT(pgprot_kernel, L_PTE_XN)
#define PAGE_KERNEL_EXEC pgprot_kernel
-#define __PAGE_NONE __pgprot(_L_PTE_DEFAULT | L_PTE_RDONLY | L_PTE_XN)
+#define __PAGE_NONE __pgprot(_L_PTE_DEFAULT | L_PTE_RDONLY | L_PTE_XN | L_PTE_NONE)
#define __PAGE_SHARED __pgprot(_L_PTE_DEFAULT | L_PTE_USER | L_PTE_XN)
#define __PAGE_SHARED_EXEC __pgprot(_L_PTE_DEFAULT | L_PTE_USER)
#define __PAGE_COPY __pgprot(_L_PTE_DEFAULT | L_PTE_USER | L_PTE_RDONLY | L_PTE_XN)
@@ -279,7 +279,7 @@ static inline pte_t pte_mkspecial(pte_t
static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
{
- const pteval_t mask = L_PTE_XN | L_PTE_RDONLY | L_PTE_USER;
+ const pteval_t mask = L_PTE_XN | L_PTE_RDONLY | L_PTE_USER | L_PTE_NONE;
pte_val(pte) = (pte_val(pte) & ~mask) | (pgprot_val(newprot) & mask);
return pte;
}
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S
@@ -166,6 +166,10 @@
tst r1, #L_PTE_YOUNG
tstne r1, #L_PTE_PRESENT
moveq r3, #0
+#ifndef CONFIG_CPU_USE_DOMAINS
+ tstne r1, #L_PTE_NONE
+ movne r3, #0
+#endif
str r3, [r0]
mcr p15, 0, r0, c7, c10, 1 @ flush_pte
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -171,6 +171,10 @@ ENTRY(cpu_v7_set_pte_ext)
tst r1, #L_PTE_YOUNG
tstne r1, #L_PTE_PRESENT
+#ifndef CONFIG_CPU_USE_DOMAINS
+ eorne r1, r1, #L_PTE_NONE
+ tstne r1, #L_PTE_NONE
+#endif
moveq r3, #0
ARM( str r3, [r0, #2048]! )
--
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