On Fri, Nov 30, 2018 at 12:28:26PM +0100, Ard Biesheuvel wrote:
> GetMemoryRegion() is used to obtain the attributes of an existing
> mapping, to permit permission attribute changes to be optimized
> away if the attributes don't actually change.
>
> The current ARM code assumes that a section mapping or a page mapping
> exists for any region passed into GetMemoryRegion(), but the region
> may be unmapped entirely, in which case the code will crash. So check
> if a section mapping exists before dereferencing it.
>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindh...@linaro.org>
> ---
> ArmPkg/Drivers/CpuDxe/Arm/Mmu.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c b/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
> index 12ca5b26673e..3b29d33d0a9c 100644
> --- a/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
> +++ b/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
> @@ -457,6 +457,9 @@ GetMemoryRegion (
>
> // Get the section at the given index
> SectionDescriptor = FirstLevelTable[TableIndex];
> + if (!SectionDescriptor) {
> + return EFI_NOT_FOUND;
> + }
>
> // If 'BaseAddress' belongs to the section then round it to the section
> boundary
> if (((SectionDescriptor & TT_DESCRIPTOR_SECTION_TYPE_MASK) ==
> TT_DESCRIPTOR_SECTION_TYPE_SECTION) ||
> --
> 2.19.1
>
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