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arm64: mm: fix thinko in non-global page table attribute check 

The routine pgattr_change_is_safe() was extended in commit 4e60205655
("arm64: mm: Permit transitioning from Global to Non-Global without BBM")
to permit changing the nG attribute from not set to set, but did so in a
way that inadvertently disallows such changes if other permitted attribute
changes take place at the same time. So update the code to take this into
account.

Fixes: 4e60205655 ("arm64: mm: Permit transitioning from Global to ...")
Cc: <stable@vger.kernel.org> # 4.14.x-
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Ard Biesheuvel 2018-02-23 18:04:48 +00:00 committed by Catalin Marinas
parent 4a3928c6f8
commit 753e8abc36
1 changed files with 4 additions and 4 deletions
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8
arch/arm64/mm/mmu.c
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@ -108,7 +108,7 @@ static bool pgattr_change_is_safe(u64 old, u64 new)
* The following mapping attributes may be updated in live
* kernel mappings without the need for break-before-make.
*/
static const pteval_t mask = PTE_PXN | PTE_RDONLY | PTE_WRITE;
static const pteval_t mask = PTE_PXN | PTE_RDONLY | PTE_WRITE | PTE_NG;
/* creating or taking down mappings is always safe */
if (old == 0 || new == 0)
@ -118,9 +118,9 @@ static bool pgattr_change_is_safe(u64 old, u64 new)
if ((old | new) & PTE_CONT)
return false;
/* Transitioning from Global to Non-Global is safe */
if (((old ^ new) == PTE_NG) && (new & PTE_NG))
return true;
/* Transitioning from Non-Global to Global is unsafe */
if (old & ~new & PTE_NG)
return false;
return ((old ^ new) & ~mask) == 0;
}