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Message-ID: <20200220195149.xha7jltmfzs3xs7g@wittgenstein>
Date: Thu, 20 Feb 2020 20:51:49 +0100
From: Christian Brauner <christian.brauner@...ntu.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "David S. Miller" <davem@...emloft.net>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
"Rafael J. Wysocki" <rafael@...nel.org>,
Pavel Machek <pavel@....cz>, Jakub Kicinski <kuba@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Stephen Hemminger <stephen@...workplumber.org>,
linux-pm@...r.kernel.org
Subject: Re: [PATCH net-next v3 2/9] sysfs: add sysfs_link_change_owner()
On Thu, Feb 20, 2020 at 12:14:43PM +0100, Greg Kroah-Hartman wrote:
> On Tue, Feb 18, 2020 at 05:29:36PM +0100, Christian Brauner wrote:
> > Add a helper to change the owner of a sysfs link.
> > This function will be used to correctly account for kobject ownership
> > changes, e.g. when moving network devices between network namespaces.
> >
> > Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
> > ---
> > /* v2 */
> > - Greg Kroah-Hartman <gregkh@...uxfoundation.org>:
> > - Add comment how ownership of sysfs object is changed.
> >
> > /* v3 */
> > - Greg Kroah-Hartman <gregkh@...uxfoundation.org>:
> > - Add explicit uid/gid parameters.
> > ---
> > fs/sysfs/file.c | 40 ++++++++++++++++++++++++++++++++++++++++
> > include/linux/sysfs.h | 10 ++++++++++
> > 2 files changed, 50 insertions(+)
> >
> > diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
> > index 32bb04b4d9d9..df5107d7b3fd 100644
> > --- a/fs/sysfs/file.c
> > +++ b/fs/sysfs/file.c
> > @@ -570,6 +570,46 @@ static int internal_change_owner(struct kernfs_node *kn, struct kobject *kobj,
> > return kernfs_setattr(kn, &newattrs);
> > }
> >
> > +/**
> > + * sysfs_link_change_owner - change owner of a link.
> > + * @kobj: object of the kernfs_node the symlink is located in.
> > + * @targ: object of the kernfs_node the symlink points to.
> > + * @name: name of the link.
> > + * @kuid: new owner's kuid
> > + * @kgid: new owner's kgid
> > + */
> > +int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
> > + const char *name, kuid_t kuid, kgid_t kgid)
> > +{
> > + struct kernfs_node *parent, *kn = NULL;
> > + int error;
> > +
> > + if (!kobj)
> > + parent = sysfs_root_kn;
> > + else
> > + parent = kobj->sd;
>
> I don't understand this, why would (!kobj) ever be a valid situation?
Yeah, a caller could just pass in "sysfs_root_kn" itself if they for
some reason needed to.
>
> > + if (!targ->state_in_sysfs)
> > + return -EINVAL;
>
> Should you also check kobj->state_in_sysfs as well?
Probably. I'll take a closer look now.
Thanks!
Christian
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