linux-kernel - Re: [PATCH v3 2/5] KVM: MMU: check guest CR3 reserved bits based on its physical address width.

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: <35e285e7-168a-25e6-1053-c005da18c103@redhat.com>
Date:   Thu, 24 Aug 2017 17:50:10 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yu Zhang <yu.c.zhang@...ux.intel.com>, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, rkrcmar@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        xiaoguangrong@...cent.com, joro@...tes.org
Subject: Re: [PATCH v3 2/5] KVM: MMU: check guest CR3 reserved bits based on
 its physical address width.

On 24/08/2017 17:23, Yu Zhang wrote:
>>>
>>>     static inline u64 rsvd_bits(int s, int e)
>>>   {
>>> +    if (e < s)
>>> +        return 0;
>>> +
>>>       return ((1ULL << (e - s + 1)) - 1) << s;
>>>   }
>> e = s - 1 is already supported; why do you need e <= s - 2?
> 
> Sorry? I do not quite understand. When will e = s - 1?

Is there any case where e < s?  I can see that MAXPHYADDR=63 gives
rsvd_bits(63, 62), but that works.

In practice, MAXPHYADDR will never be 59 even because the PKRU bits are
at bits 59..62.

Paolo