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Commit 072b1b62 authored by Steve Capper's avatar Steve Capper
Browse files

ARM64: mm: Make PAGE_NONE pages read only and no-execute. 



If we consider the following code sequence:

	my_pte = pte_modify(entry, myprot);
	x = pte_write(my_pte);
	y = pte_exec(my_pte);

If myprot comes from a PROT_NONE page, then x and y will both be
true which is undesireable behaviour.

This patch sets the no-execute and read-only bits for PAGE_NONE
such that the code above will return false for both x and y.

Signed-off-by: default avatarSteve Capper <steve.capper@linaro.org>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent f6bc87c3

arch/arm64/include/asm/pgtable.h

+2 −2
Original line number Diff line number Diff line
@@ -66,7 +66,7 @@ extern pgprot_t pgprot_default; 


#define _MOD_PROT(p, b)		__pgprot_modify(p, 0, b)



#define PAGE_NONE		__pgprot_modify(pgprot_default, PTE_TYPE_MASK, PTE_PROT_NONE)

#define PAGE_NONE		__pgprot_modify(pgprot_default, PTE_TYPE_MASK, PTE_PROT_NONE | PTE_RDONLY | PTE_PXN | PTE_UXN)

#define PAGE_SHARED		_MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)

#define PAGE_SHARED_EXEC	_MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN)

#define PAGE_COPY		_MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
@@ -76,7 +76,7 @@ extern pgprot_t pgprot_default; 
#define PAGE_KERNEL		_MOD_PROT(pgprot_default, PTE_PXN | PTE_UXN | PTE_DIRTY)

#define PAGE_KERNEL_EXEC	_MOD_PROT(pgprot_default, PTE_UXN | PTE_DIRTY)



#define __PAGE_NONE		__pgprot(((_PAGE_DEFAULT) & ~PTE_TYPE_MASK) | PTE_PROT_NONE)

#define __PAGE_NONE		__pgprot(((_PAGE_DEFAULT) & ~PTE_TYPE_MASK) | PTE_PROT_NONE | PTE_RDONLY | PTE_PXN | PTE_UXN)

#define __PAGE_SHARED		__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)

#define __PAGE_SHARED_EXEC	__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN)

#define __PAGE_COPY		__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)