linux-kernel - Re: [PATCH v3 03/28] drm/i915/gvt: Verify hugepages are contiguous in physical address space

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZGNO5gYKOhhnslsp@yzhao56-desk.sh.intel.com>
Date:   Tue, 16 May 2023 17:37:42 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>, <kvm@...r.kernel.org>,
        <intel-gvt-dev@...ts.freedesktop.org>,
        <intel-gfx@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH v3 03/28] drm/i915/gvt: Verify hugepages are contiguous
 in physical address space

hi Sean

Do you think it's necessary to double check that struct page pointers
are also contiguous?

And do you like to also include a fix as below, which is to remove the
warning in vfio_device_container_unpin_pages() when npage is 0?

@ -169,7 +173,8 @@ static int gvt_pin_guest_page(struct intel_vgpu *vgpu, unsigned long gfn,
        *page = base_page;
        return 0;
 err:
-       gvt_unpin_guest_page(vgpu, gfn, npage * PAGE_SIZE);
+       if (npage)
+               gvt_unpin_guest_page(vgpu, gfn, npage * PAGE_SIZE);
        return ret;
 }

BTW, I've sent a separate fix for vfio_iommu_type1_pin_pages() to ensure
struct page is a valid address.
https://lore.kernel.org/lkml/20230516093007.15234-1-yan.y.zhao@intel.com/

On Fri, May 12, 2023 at 05:35:35PM -0700, Sean Christopherson wrote:
> When shadowing a GTT entry with a 2M page, verify that the pfns are
> contiguous, not just that the struct page pointers are contiguous.  The
> memory map is virtual contiguous if "CONFIG_FLATMEM=y ||
> CONFIG_SPARSEMEM_VMEMMAP=y", but not for "CONFIG_SPARSEMEM=y &&
> CONFIG_SPARSEMEM_VMEMMAP=n", so theoretically KVMGT could encounter struct
> pages that are virtually contiguous, but not physically contiguous.
> 
> In practice, this flaw is likely a non-issue as it would cause functional
> problems iff a section isn't 2M aligned _and_ is directly adjacent to
> another section with discontiguous pfns.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  drivers/gpu/drm/i915/gvt/kvmgt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index de675d799c7d..429f0f993a13 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -161,7 +161,7 @@ static int gvt_pin_guest_page(struct intel_vgpu *vgpu, unsigned long gfn,
>  
>  		if (npage == 0)
>  			base_page = cur_page;
> -		else if (base_page + npage != cur_page) {
> +		else if (page_to_pfn(base_page) + npage != page_to_pfn(cur_page)) {
>  			gvt_vgpu_err("The pages are not continuous\n");
>  			ret = -EINVAL;
>  			npage++;
> -- 
> 2.40.1.606.ga4b1b128d6-goog
>