linux-kernel - Re: [PATCH v10 9/9] KVM: Enable and expose KVM_MEM

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Message-ID: <CAGtprH_pbSo1HeEFUEB6ZZxm-=NEw+nLZ6ZVvr76=9BeX=AHPA@mail.gmail.com>
Date:   Thu, 5 Jan 2023 12:38:30 -0800
From:   Vishal Annapurve <vannapurve@...gle.com>
To:     Chao Peng <chao.p.peng@...ux.intel.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        linux-doc@...r.kernel.org, qemu-devel@...gnu.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Arnd Bergmann <arnd@...db.de>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Miaohe Lin <linmiaohe@...wei.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>,
        Steven Price <steven.price@....com>,
        "Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
        ak@...ux.intel.com, david@...hat.com, aarcange@...hat.com,
        ddutile@...hat.com, dhildenb@...hat.com,
        Quentin Perret <qperret@...gle.com>, tabba@...gle.com,
        Michael Roth <michael.roth@....com>, mhocko@...e.com,
        wei.w.wang@...el.com
Subject: Re: [PATCH v10 9/9] KVM: Enable and expose KVM_MEM_PRIVATE

On Thu, Dec 1, 2022 at 10:20 PM Chao Peng <chao.p.peng@...ux.intel.com> wrote:
>
> +#ifdef CONFIG_HAVE_KVM_RESTRICTED_MEM
> +static bool restrictedmem_range_is_valid(struct kvm_memory_slot *slot,
> +                                        pgoff_t start, pgoff_t end,
> +                                        gfn_t *gfn_start, gfn_t *gfn_end)
> +{
> +       unsigned long base_pgoff = slot->restricted_offset >> PAGE_SHIFT;
> +
> +       if (start > base_pgoff)
> +               *gfn_start = slot->base_gfn + start - base_pgoff;

There should be a check for overflow here in case start is a very big
value. Additional check can look like:
if (start >= base_pgoff + slot->npages)
       return false;

> +       else
> +               *gfn_start = slot->base_gfn;
> +
> +       if (end < base_pgoff + slot->npages)
> +               *gfn_end = slot->base_gfn + end - base_pgoff;

If "end" is smaller than base_pgoff, this can cause overflow and
return the range as valid. There should be additional check:
if (end < base_pgoff)
         return false;


> +       else
> +               *gfn_end = slot->base_gfn + slot->npages;
> +
> +       if (*gfn_start >= *gfn_end)
> +               return false;
> +
> +       return true;
> +}
> +