Re: [Xen-devel] [PATCH 4/6] sysctl: use xmalloc_array() for XEN_SYSCTL_page_offline_op

[Jan Beulich <jbeulich@xxxxxxxx>]

On 05.02.2020 15:34, Julien Grall wrote:
> On 05/02/2020 13:16, Jan Beulich wrote:
>> This is more robust than the raw xmalloc_bytes().
>>
>> Also add a sanity check on the input page range.
> 
> It feels to me that the commit message/title should focus on the sanity 
> check. The xmalloc_array() is just a cleanup is "less important".

But it not being there would generally just result in -ENOMEM
due to the xmalloc_...() failing (leaving aside overflow not
accounted for in the old code), which by the new check just
gets changed into the more applicable -EINVAL. I view the
changed called out in the title as more important.

Jan

>> --- a/xen/common/sysctl.c
>> +++ b/xen/common/sysctl.c
>> @@ -187,13 +187,17 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
>>           uint32_t *status, *ptr;
>>           mfn_t mfn;
>>   
>> +        ret = -EINVAL;
>> +        if ( op->u.page_offline.end < op->u.page_offline.start )
>> +            break;
>> +
>>           ret = xsm_page_offline(XSM_HOOK, op->u.page_offline.cmd);
>>           if ( ret )
>>               break;
>>   
>> -        ptr = status = xmalloc_bytes( sizeof(uint32_t) *
>> -                                (op->u.page_offline.end -
>> -                                  op->u.page_offline.start + 1));
>> +        ptr = status = xmalloc_array(uint32_t,
>> +                                     (op->u.page_offline.end -
>> +                                      op->u.page_offline.start + 1));
>>           if ( !status )
>>           {
>>               dprintk(XENLOG_WARNING, "Out of memory for page offline op\n");
>>
> 


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