[net-next,v3,2/9] sysfs: add sysfs_link_change_owner()
diff mbox series

Message ID 20200218162943.2488012-3-christian.brauner@ubuntu.com
State Superseded, archived
Headers show
Series
  • net: fix sysfs permssions when device changes network
Related show

Commit Message

Christian Brauner Feb. 18, 2020, 4:29 p.m. UTC
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@ubuntu.com>
---
/* v2 */
-  Greg Kroah-Hartman <gregkh@linuxfoundation.org>:
   - Add comment how ownership of sysfs object is changed.

/* v3 */
-  Greg Kroah-Hartman <gregkh@linuxfoundation.org>:
   - Add explicit uid/gid parameters.
---
 fs/sysfs/file.c       | 40 ++++++++++++++++++++++++++++++++++++++++
 include/linux/sysfs.h | 10 ++++++++++
 2 files changed, 50 insertions(+)

Comments

Greg Kroah-Hartman Feb. 20, 2020, 11:14 a.m. UTC | #1
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@ubuntu.com>
> ---
> /* v2 */
> -  Greg Kroah-Hartman <gregkh@linuxfoundation.org>:
>    - Add comment how ownership of sysfs object is changed.
> 
> /* v3 */
> -  Greg Kroah-Hartman <gregkh@linuxfoundation.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?

> +	if (!targ->state_in_sysfs)
> +		return -EINVAL;

Should you also check kobj->state_in_sysfs as well?

thanks,

greg k-h
Christian Brauner Feb. 20, 2020, 7:51 p.m. UTC | #2
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@ubuntu.com>
> > ---
> > /* v2 */
> > -  Greg Kroah-Hartman <gregkh@linuxfoundation.org>:
> >    - Add comment how ownership of sysfs object is changed.
> > 
> > /* v3 */
> > -  Greg Kroah-Hartman <gregkh@linuxfoundation.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

Patch
diff mbox series

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;
+
+	if (!targ->state_in_sysfs)
+		return -EINVAL;
+
+	error = -ENOENT;
+	kn = kernfs_find_and_get_ns(parent, name, targ->sd->ns);
+	if (!kn)
+		goto out;
+
+	error = -EINVAL;
+	if (kernfs_type(kn) != KERNFS_LINK)
+		goto out;
+	if (kn->symlink.target_kn->priv != targ)
+		goto out;
+
+	error = internal_change_owner(kn, targ, kuid, kgid);
+
+out:
+	kernfs_put(kn);
+	return error;
+}
+
 /**
  *	sysfs_file_change_owner_by_name - change owner of a file.
  *	@kobj:	object.
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index c11d11c78713..899500950410 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -313,6 +313,8 @@  static inline void sysfs_enable_ns(struct kernfs_node *kn)
 int sysfs_file_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid);
 int sysfs_file_change_owner_by_name(struct kobject *kobj, const char *name,
 				    kuid_t kuid, kgid_t kgid);
+int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
+			    const char *name, kuid_t kuid, kgid_t kgid);
 
 #else /* CONFIG_SYSFS */
 
@@ -539,6 +541,14 @@  static inline int sysfs_file_change_owner_by_name(struct kobject *kobj,
 	return 0;
 }
 
+static inline int sysfs_link_change_owner(struct kobject *kobj,
+					  struct kobject *targ,
+					  const char *name, kuid_t kuid,
+					  kgid_t kgid)
+{
+	return 0;
+}
+
 #endif /* CONFIG_SYSFS */
 
 static inline int __must_check sysfs_create_file(struct kobject *kobj,