On 10/31/2017 12:01 PM, Yisheng Xie wrote:
>
>
> On 2017/10/31 17:30, Vlastimil Babka wrote:
>> On 10/27/2017 12:14 PM, Yisheng Xie wrote:
>>> + /*
>>> + * When the user specified more nodes than supported just check
>>> + * if the non supported part is all zero.
>>> + *
>>> + * If maxnode have more longs than MAX_NUMNODES, check
>>> + * the bits in that area first. And then go through to
>>> + * check the rest bits which equal or bigger than MAX_NUMNODES.
>>> + * Otherwise, just check bits [MAX_NUMNODES, maxnode).
>>> + */
>>> if (nlongs > BITS_TO_LONGS(MAX_NUMNODES)) {
>>> for (k = BITS_TO_LONGS(MAX_NUMNODES); k < nlongs; k++) {
>>> - unsigned long t;
>>> if (get_user(t, nmask + k))
>>> return -EFAULT;
>>> if (k == nlongs - 1) {
>>> @@ -1294,6 +1301,16 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
>>> endmask = ~0UL;
>>> }
>>>
>>> + if (maxnode > MAX_NUMNODES && MAX_NUMNODES % BITS_PER_LONG != 0) {
>>> + unsigned long valid_mask = endmask;
>>> +
>>> + valid_mask &= ~((1UL << (MAX_NUMNODES % BITS_PER_LONG)) - 1);
>>
>> I'm not sure if the combination with endmask works in this case:
>>
>> 0 BITS_PER_LONG 2xBITS_PER_LONG
>> |____________|____________|
>> | |
>> MAX_NUMNODES maxnode
>>
>> endmask will contain bits between 0 and maxnode
>
> In the case, BITS_TO_LONGS(maxnode) > BITS_TO_LONGS(MAX_NUMNODES), right?
> And after checking BITS_PER_LONG to 2xBITS_PER_LONG，endmask will set to
> "~0UL". e.g. endmask will be 0xffff ffff ffff ffff if
> unsigned long is 64bit.
>
> Then the valid_mask will just contain bits MAX_NUMNODES to BITS_PER_LONG.
Ugh, right. I missed that. This code is not simple...
> Thanks
> Yisheng Xie
>
>> but here we want to check bits between MAX_NUMNODES and BITS_PER_LONG
>> and endmask should not be mixed up with that?
>>
>>
>> Vlastimil
>>
>
>
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