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 22:04:33 -0600
From:   Kelsey Skunberg <skunberg.kelsey@...il.com>
To:     Don Dutile <ddutile@...hat.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 Wed, Sep 04, 2019 at 02:33:44PM -0400, Don Dutile wrote:
> 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
>

Thank you for checking into this and getting back so quick! I'll cc you in
the patch. :)

Thanks again!

-Kelsey