linux-kernel - Re: [PATCH] x86/xen: add physically contiguous check to xen_destroy_contiguous

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Date:   Thu, 25 Oct 2018 21:17:10 -0700
From:   Joe Jin <joe.jin@...cle.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        "DONGLI.ZHANG" <dongli.zhang@...cle.com>,
        John Sobecki <john.sobecki@...cle.com>
Cc:     "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        konrad@...nel.org
Subject: Re: [PATCH] x86/xen: add physically contiguous check to
 xen_destroy_contiguous_region

I did not realized range_straddles_page_boundary() only available
on xen-swiotlb, please ignore this patch.

Sorry for the bother.

Thanks,
Joe
On 10/25/18 5:16 PM, Joe Jin wrote:
> xen_destroy_contiguous_region() used to exchange physically
> contiguous memory with hypervisor, but it does not verify
> that the memory is physically contiguous or no, passing
> non-contiguous memory to xen_destroy_contiguous_region()
> will lead kernel panic.
> 
> Signed-off-by: Joe Jin <joe.jin@...cle.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: Juergen Gross <jgross@...e.com>
> ---
>  arch/x86/xen/mmu_pv.c     | 3 +++
>  drivers/xen/swiotlb-xen.c | 3 +--
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
> index 70ea598a37d2..c2f081f8ebe3 100644
> --- a/arch/x86/xen/mmu_pv.c
> +++ b/arch/x86/xen/mmu_pv.c
> @@ -2649,6 +2649,9 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
>  	if (unlikely(order > MAX_CONTIG_ORDER))
>  		return;
>  
> +	if (range_straddles_page_boundary(pstart, PAGE_SIZE << order))
> +		return;
> +
>  	vstart = (unsigned long)phys_to_virt(pstart);
>  	memset((void *) vstart, 0, PAGE_SIZE << order);
>  
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index f5c1af4ce9ab..432eeae02d7d 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -357,8 +357,7 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
>  	/* Convert the size to actually allocated. */
>  	size = 1UL << (order + XEN_PAGE_SHIFT);
>  
> -	if (((dev_addr + size - 1 <= dma_mask)) ||
> -	    range_straddles_page_boundary(phys, size))
> +	if (dev_addr + size - 1 <= dma_mask)
>  		xen_destroy_contiguous_region(phys, order);
>  
>  	xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
>