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sysfs: add sysfs_file_change_owner()

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Add helpers to change the owner of a sysfs files.
This function will be used to correctly account for kobject ownership
changes, e.g. when moving network devices between network namespaces.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Christian Brauner 2020-02-27 04:37:11 +01:00 committed by David S. Miller
parent d1c73cbdf9
commit f70ce18568
2 changed files with 57 additions and 0 deletions
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47
fs/sysfs/file.c
View file

@ -558,3 +558,50 @@ 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, kuid_t kuid,
kgid_t kgid)
{
struct iattr newattrs = {
.ia_valid = ATTR_UID | ATTR_GID,
.ia_uid = kuid,
.ia_gid = kgid,
};
return kernfs_setattr(kn, &newattrs);
}
/**
* sysfs_file_change_owner - change owner of a sysfs file.
* @kobj: object.
* @name: name of the file to change.
* @kuid: new owner's kuid
* @kgid: new owner's kgid
*
* This function looks up the sysfs entry @name under @kobj and changes the
* ownership to @kuid/@kgid.
*
* Returns 0 on success or error code on failure.
*/
int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
kgid_t kgid)
{
struct kernfs_node *kn;
int error;
if (!name)
return -EINVAL;
if (!kobj->state_in_sysfs)
return -EINVAL;
kn = kernfs_find_and_get(kobj->sd, name);
if (!kn)
return -ENOENT;
error = internal_change_owner(kn, kuid, kgid);
kernfs_put(kn);
return error;
}
EXPORT_SYMBOL_GPL(sysfs_file_change_owner);

10
include/linux/sysfs.h
View file

@ -310,6 +310,9 @@ static inline void sysfs_enable_ns(struct kernfs_node *kn)
return kernfs_enable_ns(kn);
}
int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
kgid_t kgid);
#else /* CONFIG_SYSFS */
static inline int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
@ -522,6 +525,13 @@ static inline void sysfs_enable_ns(struct kernfs_node *kn)
{
}
static inline int sysfs_file_change_owner(struct kobject *kobj,
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,