Re: [dpdk-dev] [PATCH] eal/linux: fix memory allocations in containers+SELinux

[Aaron Conole <aconole@redhat.com>]

"Burakov, Anatoly" <anatoly.burakov@intel.com> writes:

> On 17-Sep-20 2:47 PM, David Marchand wrote:
>> On Fri, Sep 11, 2020 at 2:46 PM Burakov, Anatoly
>> <anatoly.burakov@intel.com> wrote:
>>>> Removing hugepage files is done in multiple places and the memory
>>>> allocation code is complex.
>>>> This fix tries to do the minimum and avoids touching other paths.
>>>>
>>>> If trying to remove the hugepage file before allocating a page fails,
>>>> the error is reported to the caller and the user will see a memory
>>>> allocation error log.
>>>>
>>>> Fixes: 582bed1e1d1d ("mem: support mapping hugepages at runtime")
>>>> Cc: stable@dpdk.org
>>>>
>>>> Signed-off-by: David Marchand <david.marchand@redhat.com>
>>>> ---
>>>
>>> I believe only the primary will try to allocate new pages, but this only
>>> covers the page-per-file scenario. There's also legacy mem option (which
>>> would attempt to remove files prior to creating new ones - not sure if
>>> it's refused in that case), and single file segments option (which will
>>> mostly fallocate holes rather than delete files, but may still attempt
>>> to delete files - by the way, how does fallocate work with SELinux?).
>>
>> This issue should only concern part of the memory allocator that deals
>> with "named files" backed hugepages.
>> I would focus on the code relying on eal_get_hugefile_path() and I
>> agree I might have missed the legacy-mem part.
>>
>> For anonymous hugepages this should not matter.
>>
>>
>
> Anonymous hugepages shouldn't matter, yes, but single-file segments
> mode does fallocate() and remove - you have the remove part covered,
> but i'm just curious if fallocate() would also cause any issues with
> SELinux.

I think it might depend on the policy, file types, and labels allowed
for the process.  I did a little bit of digging but didn't find anything
that specifically targets that call.  I guess it may be something like:

  allow dom_t obj_t:file { getattr setattr appent ioctl lock open read
                           write };

BUT that's just a guess without any real testing.