Re: [PATCH v4 3/4] fpga: dfl: add basic support DFHv1

matthew.gerlach
2022-10-31T20:15:12Z

On Mon, 31 Oct 2022, Andy Shevchenko wrote:

> On Mon, Oct 31, 2022 at 09:16:19AM +0800, Xu Yilun wrote:
>> On 2022-10-31 at 00:06:28 +0200, Andy Shevchenko wrote:
>>> On Sat, Oct 29, 2022 at 09:08:44PM +0800, Xu Yilun wrote:
>>>> On 2022-10-20 at 14:26:09 -0700, matthew.gerlach@linux.intel.com wrote:
>>>
>>>>> struct dfl_feature_info {
>>>>> u16 fid;
>>>>> u8 revision;
>>>>> + u8 dfh_version;
>>>>> struct resource mmio_res;
>>>>> void __iomem *ioaddr;
>>>>> struct list_head node;
>>>>> unsigned int irq_base;
>>>>> unsigned int nr_irqs;
>>>>> + unsigned int param_size;
>>>>> + u64 params[];
>>>>> };
>>>
>>> ...
>>>
>>>>> + finfo = kzalloc(sizeof(*finfo) + dfh_psize, GFP_KERNEL);
>>>
>>>
>>> This probably may use something from overflow.h.
>>>
>>>> The u64 flexible array in the structure, but seems dfh_get_psize could
>>>> not garantee 64bit aligned size.
>>>>
>>>> What's the mandatory alignment of param data? If 64bit aligned, bit 33-34
>>>> of PARAM_HDR should be reserved. If 32bit aligned, finfo:params should be
>>>> u32[].
>>>
>>> Isn't it guaranteed by the C standard / architecture ABI?
>>
>> I'm referring to the malloc size of the structure. It reserved dfh_psize
>> bytes for this u64 array, but there is no garantee dfh_psize should be a
>> multiple of 8. So there may be memory leak when accessing the last
>> array element?
>
> Have you looked at macros in the overflow.h? Would the use of it solve your
> concern?

By clarifying the definition of the next field in the parameter header
as the number of 8-byte words, dfh_get_psize is guaranteed to be a multiple of 8.
This is fixed in the next revision of patches.

Matthew Gerlach

>
> --
> With Best Regards,
> Andy Shevchenko
>
>
>