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Re: [Xen-devel] [PATCH V3] x86/altp2m: Hypercall to set altp2m view visibility
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>
- Date: Thu, 20 Feb 2020 09:59:59 +0000
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- Cc: Kevin Tian <kevin.tian@xxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Wei Liu <wl@xxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Ian Jackson <ian.jackson@xxxxxxxxxxxxx>, Jun Nakajima <jun.nakajima@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Thu, 20 Feb 2020 10:00:36 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHV5wWKuFf2vClElk6nKYx34YpPrKgivhiAgAEc4IA=
- Thread-topic: [PATCH V3] x86/altp2m: Hypercall to set altp2m view visibility
On 19.02.2020 19:00, Jan Beulich wrote:
> On 19.02.2020 10:18, Alexandru Stefan ISAILA wrote:
>> @@ -4835,6 +4836,23 @@ static int do_altp2m_op(
>> break;
>> }
>>
>> + case HVMOP_altp2m_set_visibility:
>> + {
>> + uint16_t altp2m_idx = a.u.set_visibility.altp2m_idx;
>> +
>> + if ( a.u.set_visibility.pad )
>> + rc = -EINVAL;
>> + else if ( !altp2m_active(d) )
>> + rc = -EOPNOTSUPP;
>> + else if ( a.u.set_visibility.visible )
>> + d->arch.altp2m_working_eptp[altp2m_idx] =
>> + d->arch.altp2m_eptp[altp2m_idx];
>> + else
>> + d->arch.altp2m_working_eptp[altp2m_idx] =
>> + mfn_x(INVALID_MFN);
>
> Don't you need to bounds check the index before its use?
Unless we want a index out of bounds from the user. Sorry for not having
that, I will add a "altp2m_eptp[array_index_nospec(altp2m_idx,
MAX_EPTP)]" in place for the next version.
> And
> shouldn't you return an error also for in-range ones which
> aren't actually valid?
That is a good thing. Maybe -EINVAL could fit this?
And together with the bounds check it will end up something like this:
if ( !altp2m_idx < 0 || altp2m_idx >=
min(ARRAY_SIZE(d->arch.altp2m_p2m), MAX_EPTP) ||
altp2m_eptp[array_index_nospec(altp2m_idx, MAX_EPTP)] ==
mfn_x(INVALID_MFN) )
return -EINVAL;
And looking again, it could be coupled with the a.u.set_visibility.pad.
Thanks,
Alex
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