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

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: <20230106041346.GA2288017@chaop.bj.intel.com>
Date:   Fri, 6 Jan 2023 12:13:46 +0800
From:   Chao Peng <chao.p.peng@...ux.intel.com>
To:     Vishal Annapurve <vannapurve@...gle.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, Jan 05, 2023 at 12:38:30PM -0800, Vishal Annapurve wrote:
> 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;

Thanks! Both are good catches. The improved code:

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 + slot->npages)
		return false;
	else if (start <= base_pgoff)
		*gfn_start = slot->base_gfn;
	else
		*gfn_start = start - base_pgoff + slot->base_gfn;

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

	if (*gfn_start >= *gfn_end)
		return false;

	return true;
}

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