linux-kernel - Re: [Linux-kernel-mentees] [PATCH v2 2/3] PCI: sysfs: Change permissions from symbolic to octal

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Date:   Wed, 4 Sep 2019 14:33:44 -0400
From:   Don Dutile <ddutile@...hat.com>
To:     Kelsey Skunberg <skunberg.kelsey@...il.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Bodong Wang <bodong@...lanox.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [Linux-kernel-mentees] [PATCH v2 2/3] PCI: sysfs: Change
 permissions from symbolic to octal

On 09/04/2019 02:22 AM, Kelsey Skunberg wrote:
> On Thu, Aug 15, 2019 at 10:37:13AM -0400, Don Dutile wrote:
>> On 08/14/2019 01:38 AM, Bjorn Helgaas wrote:
>>> [+cc Bodong, Don, Greg for permission question]
>>>
>>> On Tue, Aug 13, 2019 at 02:45:12PM -0600, Kelsey Skunberg wrote:
>>>> Symbolic permissions such as "(S_IWUSR | S_IWGRP)" are not
>>>> preferred and octal permissions should be used instead. Change all
>>>> symbolic permissions to octal permissions.
>>>>
>>>> Example of old:
>>>>
>>>> "(S_IWUSR | S_IWGRP)"
>>>>
>>>> Example of new:
>>>>
>>>> "0220"
>>>
>>>
>>>>    static DEVICE_ATTR_RO(sriov_totalvfs);
>>>> -static DEVICE_ATTR(sriov_numvfs, (S_IRUGO | S_IWUSR | S_IWGRP),
>>>> -				  sriov_numvfs_show, sriov_numvfs_store);
>>>> +static DEVICE_ATTR(sriov_numvfs, 0664, sriov_numvfs_show, sriov_numvfs_store);
>>>>    static DEVICE_ATTR_RO(sriov_offset);
>>>>    static DEVICE_ATTR_RO(sriov_stride);
>>>>    static DEVICE_ATTR_RO(sriov_vf_device);
>>>> -static DEVICE_ATTR(sriov_drivers_autoprobe, (S_IRUGO | S_IWUSR | S_IWGRP),
>>>> -		   sriov_drivers_autoprobe_show, sriov_drivers_autoprobe_store);
>>>> +static DEVICE_ATTR(sriov_drivers_autoprobe, 0664, sriov_drivers_autoprobe_show,
>>>> +		   sriov_drivers_autoprobe_store);
>>>
>>> Greg noticed that sriov_numvfs and sriov_drivers_autoprobe have
>>> "unusual" permissions.  These were added by:
>>>
>>>     0e7df22401a3 ("PCI: Add sysfs sriov_drivers_autoprobe to control VF driver binding")
>>>     1789382a72a5 ("PCI: SRIOV control and status via sysfs")
>>>
>>> Kelsey's patch correctly preserves the existing permissions, but we
>>> should double-check that they are the permissions they want, and
>>> possibly add a comment about why they're different from the rest.
>>>
>>> Bjorn
>>>
> 
> Hi Don,
> 
>> The rest being? ... 0644 vs 0664 ?
>> The file is read & written, thus the (first) 6; I'll have to dig through very old (7 yr) notes to see if the second 6 is needed for libvirt (so it doesn't have to be root to enable).
>>
>> -dd
>>
> 
> Were you able to see if the unusual permissions (0664) are needed for
> libvirt? I appreciate your help!
> 
> -Kelsey
> 
Daniel Berrangé reported that libvirt runs as root when dealing with anything PCI, and chowns files for qemu needs, so there is no need for the 664 permission.
For all I know, it's a simple typo that was allowed to creep in. :-/

Feel free to modify to 644.

-dd