why label /dev/hugepages directory hugetlbfs_t?

[Daniel J Walsh]

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On 10/12/2010 03:45 PM, Dominick Grift wrote:
> On Tue, Oct 12, 2010 at 11:54:42AM -0400, Daniel J Walsh wrote:
> On 10/12/2010 11:34 AM, Eric Paris wrote:
>>>> On Tue, 2010-10-12 at 11:01 -0400, Daniel J Walsh wrote:
>>>>> On 10/09/2010 11:30 AM, Dominick Grift wrote:
>>>>>> On Sat, Oct 09, 2010 at 09:14:25AM -0400, Eric Paris wrote:
>>>>>>> On Sat, 2010-10-09 at 11:43 +0200, Dominick Grift wrote:
>>>>>>>> Why is /dev/hugepages specified to be labeled hugetlbfs_t? Any
>>>>>>>> particular reason for this? 
>>>>>>>>
>>>>>>>> In my branch i labelled it device_t like most directories in /dev.
>>>>>>>>
>>>>>>>> This makes it easier because udev does some magic
>>>>>>>> in /lib/udev/devices(hugetables) which causes all kinds of extra
>>>>>>>> denials if i label the hugepages dir hugetlbfs_t.
>>>>>>>>
>>>>>>>> For example hugetlbfs_t must associate to device_t etc. Much easier to
>>>>>>>> just label hugepages directories at both /dev/hugepage
>>>>>>>> and /lib/udev/devices/hugepages device_t.
>>>>>>>>
>>>>>>>> Also i noticed that /sys/fs/cgroup is specified to be labeled
>>>>>>>> cgroup_t, but i think the kernel creates that directory with type
>>>>>>>> sysfs_t. So that would mean that it needs to be restored at each
>>>>>>>> boot-up.
>>>>>>>
>>>>>>> /dev/hugepages and (I think) /sys/fs/cgroup are filesystem mount points
>>>>>>> not actually files in the devfs or sysfs filesystem.  So the labels are
>>>>>>> picked probably picked up from the filesystem labeling rules at mount
>>>>>>> time rather than from a later restorecon.
>>>>>>
>>>>>> In my branch i have the directory /dev/hugepages set to device_t and this location is labelled properly (udev or dracut did it?)
>>>>>> Unlike /sys/fs/cgroup directory which is set to cgroup_t but this location is not labelled properly (sysfs_t instead of specified cgroup_t)
>>>>>>
>>>>>>>
>>>>>>> As to whether we need or want such labels on hugetlbfs and cgroupfs I'll
>>>>>>> let you and Dan argue about   :)
>>>>
>>>>> I think the problem is running tools like restorecon on /dev to check
>>>>> labels. ends up generating errors when hugetlbfs and cgroupfs are
>>>>> mounted.  I guess we could change the label to <<none>>
>>>>>
>>>>> /dev/shm has the same problem.
>>>>>
>>>>> matchpathcon  /dev/shm
>>>>> /dev/shm	system_u:object_r:tmpfs_t:s0
>>>>
>>>> But isn't /dev/shm just a normal tmpfs, not a special FS like cgroupfs
>>>> or hugepagefs?  I'm not saying the <<none>> isn't the right answer for
>>>> things under /dev/shm/ but it's not exactly the same problem....
>>>>
>>>> -Eric
>>>>
> 
> Not sure I see the difference.  We are talking about directories on
> special file systems like /dev and /sys that have files systems mounted
> on them.
> 
> tmpfs on /dev/shm type tmpfs (rw,rootcontext="system_u:object_r:tmpfs_t:s0")
> 
> This shows that a tmpfs file system is mounted on /dev/shm.  I could
> leave /dev/shm as labeled device_t, but we label it tmpfs_t so that
> tools looking at /dev/ will not report a labeling problem.  To me this
> looks like the same thing we are doing with /dev/hugepages
> 
>> i have:
> 
>> # ls -alZ /dev | grep huge
>> drwxr-xr-x. root   root    system_u:object_r:device_t:s0    hugepages
> 
>> # semanage fcontext -l | grep hugepages
>> /dev/hugepages                                     directory          system_u:object_r:device_t:s0 
>> /dev/hugepages/.*                                  all files          <<None>>
>> /lib/udev/devices/hugepages                        directory          system_u:object_r:device_t:s0 
>> /lib/udev/devices/hugepages/.*                     all files          <<None>>
> 
>> It appears that this way i dont have to associate hugetblfs_t to device_t
>> However i am not sure because directory /dev/hugepages is empty here.
> 
>> But for me so far this works best because i run kernel confined and udev does all kinds of crazy stuff early in the boot process and this seems to work clean for me so far
> 
> 
> 
>>
>>
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Yes that will work until you mount on top of /dev/hugepages and then if
you run restorecon -R -n -v /dev it will report that /dev/hugepages is
incorrectly labeled hugetlbfs_t.
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