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Commit 47f12043 authored by Will Deacon's avatar Will Deacon Committed by Russell King
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ARM: 7487/1: mm: avoid setting nG bit for user mappings that aren't present 



Swap entries are encoding in ptes such that !pte_present(pte) and
pte_file(pte). The remaining bits of the descriptor are used to identify
the swapfile and offset within it to the swap entry.

When writing such a pte for a user virtual address, set_pte_at
unconditionally sets the nG bit, which (in the case of LPAE) will
corrupt the swapfile offset and lead to a BUG:

[  140.494067] swap_free: Unused swap offset entry 000763b4
[  140.509989] BUG: Bad page map in process rs:main Q:Reg  pte:0ec76800 pmd:8f92e003

This patch fixes the problem by only setting the nG bit for user
mappings that are actually present.

Cc: <stable@vger.kernel.org>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 237ec6f2

arch/arm/include/asm/pgtable.h

+18 −16
Original line number Diff line number Diff line
@@ -195,6 +195,18 @@ static inline pte_t *pmd_page_vaddr(pmd_t pmd) 


#define pte_clear(mm,addr,ptep)	set_pte_ext(ptep, __pte(0), 0)



#define pte_none(pte)		(!pte_val(pte))

#define pte_present(pte)	(pte_val(pte) & L_PTE_PRESENT)

#define pte_write(pte)		(!(pte_val(pte) & L_PTE_RDONLY))

#define pte_dirty(pte)		(pte_val(pte) & L_PTE_DIRTY)

#define pte_young(pte)		(pte_val(pte) & L_PTE_YOUNG)

#define pte_exec(pte)		(!(pte_val(pte) & L_PTE_XN))

#define pte_special(pte)	(0)



#define pte_present_user(pte) \

	((pte_val(pte) & (L_PTE_PRESENT | L_PTE_USER)) == \

	 (L_PTE_PRESENT | L_PTE_USER))



#if __LINUX_ARM_ARCH__ < 6

static inline void __sync_icache_dcache(pte_t pteval)

{
@@ -206,25 +218,15 @@ extern void __sync_icache_dcache(pte_t pteval); 
static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,

			      pte_t *ptep, pte_t pteval)

{

	if (addr >= TASK_SIZE)

		set_pte_ext(ptep, pteval, 0);

	else {

	unsigned long ext = 0;



	if (addr < TASK_SIZE && pte_present_user(pteval)) {

		__sync_icache_dcache(pteval);

		set_pte_ext(ptep, pteval, PTE_EXT_NG);

	}

		ext |= PTE_EXT_NG;

	}



#define pte_none(pte)		(!pte_val(pte))

#define pte_present(pte)	(pte_val(pte) & L_PTE_PRESENT)

#define pte_write(pte)		(!(pte_val(pte) & L_PTE_RDONLY))

#define pte_dirty(pte)		(pte_val(pte) & L_PTE_DIRTY)

#define pte_young(pte)		(pte_val(pte) & L_PTE_YOUNG)

#define pte_exec(pte)		(!(pte_val(pte) & L_PTE_XN))

#define pte_special(pte)	(0)



#define pte_present_user(pte) \

	((pte_val(pte) & (L_PTE_PRESENT | L_PTE_USER)) == \

	 (L_PTE_PRESENT | L_PTE_USER))

	set_pte_ext(ptep, pteval, ext);

}



#define PTE_BIT_FUNC(fn,op) \

static inline pte_t pte_##fn(pte_t pte) { pte_val(pte) op; return pte; }

arch/arm/mm/flush.c

+0 −2
Original line number Diff line number Diff line
@@ -231,8 +231,6 @@ void __sync_icache_dcache(pte_t pteval) 
	struct page *page;

	struct address_space *mapping;



	if (!pte_present_user(pteval))

		return;

	if (cache_is_vipt_nonaliasing() && !pte_exec(pteval))

		/* only flush non-aliasing VIPT caches for exec mappings */

		return;