From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir@xen.org>
Subject: Re: [PATCH] xen: Fix xenctl_cpumap_to_cpumask buffer
 size check
Date: Tue, 13 Nov 2012 10:10:31 +0000
Message-ID: <CCC7CD17.5206A%keir@xen.org>
References: <50A214B902000078000A7F88@nat28.tlf.novell.com>
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To: Jan Beulich <JBeulich@suse.com>, Matthew Daley <mattjd@gmail.com>
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On 13/11/2012 08:36, "Jan Beulich" <JBeulich@suse.com> wrote:

>> Fix by using the correct cpumask buffer size in place of sizeof.
>> 
>> Signed-off-by: Matthew Daley <mattjd@gmail.com>
> 
> Acked-by: Jan Beulich <jbeulich@suse.com>
> 
> However, I would have preferred the adjustment to be ...
> 
>> diff --git a/xen/common/domctl.c b/xen/common/domctl.c
>> index e153cb4..204e951 100644
>> --- a/xen/common/domctl.c
>> +++ b/xen/common/domctl.c
>> @@ -78,7 +78,7 @@ int xenctl_cpumap_to_cpumask(
>>      {
>>          if ( copy_from_guest(bytemap, xenctl_cpumap->bitmap, copy_bytes) )
>>              err = -EFAULT;
>> -        if ( (xenctl_cpumap->nr_cpus & 7) && (guest_bytes <=
>> sizeof(bytemap)) )
>> +        if ( (xenctl_cpumap->nr_cpus & 7) && (guest_bytes <= (nr_cpu_ids +
>> 7) / 8) )
> 
>         if ( (xenctl_cpumap->nr_cpus & 7) && (guest_bytes <= copy_bytes) )
> 
> or even (considering that guest_bytes >= copy_bytes due to the
> way copy_bytes gets initialized)
> 
>         if ( (xenctl_cpumap->nr_cpus & 7) && (guest_bytes == copy_bytes) )
> 
> to make explicit when exactly the masking is necessary.

Any of the three alternatives is fine by me.

Acked-by: Keir Fraser <keir@xen.org>