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SubjectRe: [PATCH net-next 01/10] sysfs: add sysfs_file_change_owner()
On Wed, Feb 12, 2020 at 11:43:12AM +0100, Christian Brauner wrote:
> Add a helper to change the owner of a sysfs file.
> The ownership of a sysfs object is determined based on the ownership of
> the corresponding kobject, i.e. only if the ownership of a kobject is
> changed will this function change the ownership of the corresponding
> sysfs entry.
> 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>
> ---
> fs/sysfs/file.c | 46 +++++++++++++++++++++++++++++++++++++++++++
> include/linux/sysfs.h | 7 +++++++
> 2 files changed, 53 insertions(+)
>
> diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
> index 130fc6fbcc03..007b97ca8165 100644
> --- a/fs/sysfs/file.c
> +++ b/fs/sysfs/file.c
> @@ -558,3 +558,49 @@ void sysfs_remove_bin_file(struct kobject *kobj,
> kernfs_remove_by_name(kobj->sd, attr->attr.name);
> }
> EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
> +
> +static int internal_change_owner(struct kernfs_node *kn, struct kobject *kobj)
> +{
> + kuid_t uid;
> + kgid_t gid;
> + struct iattr newattrs = {
> + .ia_valid = ATTR_UID | ATTR_GID,
> + };
> +
> + kobject_get_ownership(kobj, &uid, &gid);
> + newattrs.ia_uid = uid;
> + newattrs.ia_gid = gid;
> +
> + return kernfs_setattr(kn, &newattrs);
> +}
> +
> +/**
> + * sysfs_file_change_owner - change owner of a file.
> + * @kobj: object.
> + * @name: name of the file to change.
> + * can be NULL to change current file.
> + */
> +int sysfs_file_change_owner(struct kobject *kobj, const char *name)

Same meta-question I did for the other call, what does this set the file
owner to? How to you specify this?

I understand your overall goal/need here, I'm just not understanding how
this actually changes anything.

lost,

greg k-h

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