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Re: [Xen-devel] [PATCH V7 1/4] x86/mm: Add array_index_nospec to guest provided index values
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>
- Date: Fri, 17 Jan 2020 08:48:42 +0000
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- Cc: Petre Ovidiu PIRCALABU <ppircalabu@xxxxxxxxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, Tamas K Lengyel <tamas@xxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Razvan COJOCARU <rcojocaru@xxxxxxxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Jun Nakajima <jun.nakajima@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Fri, 17 Jan 2020 08:49:12 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [Xen-devel] [PATCH V7 1/4] x86/mm: Add array_index_nospec to guest provided index values
On 10.01.2020 18:12, Jan Beulich wrote:
> On 08.01.2020 15:08, Alexandru Stefan ISAILA wrote:
>> Changes since V6:
>> - Remove stray spaces
>> - Use ARRAY_SIZE(d->arch.altp2m_p2m) insead of MAX_ALTP2M.
>
> I'm not utterly confused:
>
>> --- a/xen/arch/x86/mm/mem_access.c
>> +++ b/xen/arch/x86/mm/mem_access.c
>> @@ -366,11 +366,13 @@ long p2m_set_mem_access(struct domain *d, gfn_t gfn,
>> uint32_t nr,
>> #ifdef CONFIG_HVM
>> if ( altp2m_idx )
>> {
>> - if ( altp2m_idx >= MAX_ALTP2M ||
>> - d->arch.altp2m_eptp[altp2m_idx] == mfn_x(INVALID_MFN) )
>> + if ( altp2m_idx >= min(ARRAY_SIZE(d->arch.altp2m_p2m), MAX_EPTP) ||
>> + d->arch.altp2m_eptp[array_index_nospec(altp2m_idx, MAX_EPTP)]
>> ==
>> + mfn_x(INVALID_MFN) )
>> return -EINVAL;
>>
>> - ap2m = d->arch.altp2m_p2m[altp2m_idx];
>> + ap2m = d->arch.altp2m_p2m[array_index_nospec(altp2m_idx,
>> + ARRAY_SIZE(d->arch.altp2m_p2m))];
>
> Why is this still not
>
> ap2m = array_access_nospec(d->arch.altp2m_p2m, altp2m_idx);
>
> ? What am I missing?
>
Sorry for the misunderstanding here, I will use array_access_nospec()
where the ARRAY_SIZE(d->arch.altp2m_p2m) is used.
Alex
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