linux-kernel - RE: [PATCH 4.9 09/66] KVM: arm/arm64: Check pagesize when allocating a hugepage at Stage 2

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Date:   Wed, 28 Feb 2018 15:33:03 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Punit Agrawal <punit.agrawal@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <christoffer.dall@...aro.org>
Subject: RE: [PATCH 4.9 09/66] KVM: arm/arm64: Check pagesize when allocating
 a hugepage at Stage 2

> 4.9-stable review patch.  If anyone has any objections, please let me know.

I know that my response comes late but I just found out that the version of the patch applied in 4.9-stable, the one in this email, is different than the one applied on 4.14-stable.
This is the one applied on 4.14: https://patchwork.kernel.org/patch/10177715/

As you can see, the check against PMD_SIZE which is present in 4.14 is not present in this version of the patch.

Am I missing something or should I send a patch to rectify this?

Thanks,
Ioana Ciornei

> 
> ------------------
> 
> From: Punit Agrawal <punit.agrawal@....com>
> 
> commit c507babf10ead4d5c8cca704539b170752a8ac84 upstream.
> 
> KVM only supports PMD hugepages at stage 2 but doesn't actually check that
> the provided hugepage memory pagesize is PMD_SIZE before populating
> stage 2 entries.
> 
> In cases where the backing hugepage size is smaller than PMD_SIZE (such as
> when using contiguous hugepages), KVM can end up creating stage 2
> mappings that extend beyond the supplied memory.
> 
> Fix this by checking for the pagesize of userspace vma before creating PMD
> hugepage at stage 2.
> 
> Fixes: 66b3923a1a0f77a ("arm64: hugetlb: add support for PTE contiguous
> bit")
> Signed-off-by: Punit Agrawal <punit.agrawal@....com>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Reviewed-by: Christoffer Dall <christoffer.dall@...aro.org>
> Signed-off-by: Christoffer Dall <christoffer.dall@...aro.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> ---
>  arch/arm/kvm/mmu.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -1284,7 +1284,7 @@ static int user_mem_abort(struct kvm_vcp
>  		return -EFAULT;
>  	}
> 
> -	if (is_vm_hugetlb_page(vma) && !logging_active) {
> +	if (vma_kernel_pagesize(vma) && !logging_active) {
>  		hugetlb = true;
>  		gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
>  	} else {
>