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References: <20221202061347.1070246-1-chao.p.peng@linux.intel.com> <20221202061347.1070246-10-chao.p.peng@linux.intel.com>
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From:   Vishal Annapurve <vannapurve@google.com>
Date:   Thu, 5 Jan 2023 12:38:30 -0800
Message-ID: <CAGtprH_pbSo1HeEFUEB6ZZxm-=NEw+nLZ6ZVvr76=9BeX=AHPA@mail.gmail.com>
Subject: Re: [PATCH v10 9/9] KVM: Enable and expose KVM_MEM_PRIVATE
To:     Chao Peng <chao.p.peng@linux.intel.com>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
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On Thu, Dec 1, 2022 at 10:20 PM Chao Peng <chao.p.peng@linux.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;
> +}
> +