4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
commit 753e8abc36b2c966caea075db0c845563c8a19bf upstream.
The routine pgattr_change_is_safe() was extended in commit 4e6020565596
("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: 4e6020565596 ("arm64: mm: Permit transitioning from Global to ...")
Cc: <stable@xxxxxxxxxxxxxxx> # 4.14.x-
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/mm/mmu.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -107,7 +107,7 @@ static bool pgattr_change_is_safe(u64 ol
* 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)
@@ -117,9 +117,9 @@ static bool pgattr_change_is_safe(u64 ol
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;
}