sysfs: add sysfs_group{s}_change_owner()

Add helpers to change the owner of sysfs groups.
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>

diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
index c4ab045..5afe0e7 100644 (file)
--- a/fs/sysfs/group.c
+++ b/fs/sysfs/group.c
@@ -13,6 +13,7 @@
 #include <linux/dcache.h>
 #include <linux/namei.h>
 #include <linux/err.h>
+#include <linux/fs.h>
 #include "sysfs.h"
 
 
@@ -457,3 +458,117 @@ int __compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
        return PTR_ERR_OR_ZERO(link);
 }
 EXPORT_SYMBOL_GPL(__compat_only_sysfs_link_entry_to_kobj);
+
+static int sysfs_group_attrs_change_owner(struct kernfs_node *grp_kn,
+                                         const struct attribute_group *grp,
+                                         struct iattr *newattrs)
+{
+       struct kernfs_node *kn;
+       int error;
+
+       if (grp->attrs) {
+               struct attribute *const *attr;
+
+               for (attr = grp->attrs; *attr; attr++) {
+                       kn = kernfs_find_and_get(grp_kn, (*attr)->name);
+                       if (!kn)
+                               return -ENOENT;
+
+                       error = kernfs_setattr(kn, newattrs);
+                       kernfs_put(kn);
+                       if (error)
+                               return error;
+               }
+       }
+
+       if (grp->bin_attrs) {
+               struct bin_attribute *const *bin_attr;
+
+               for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++) {
+                       kn = kernfs_find_and_get(grp_kn, (*bin_attr)->attr.name);
+                       if (!kn)
+                               return -ENOENT;
+
+                       error = kernfs_setattr(kn, newattrs);
+                       kernfs_put(kn);
+                       if (error)
+                               return error;
+               }
+       }
+
+       return 0;
+}
+
+/**
+ * sysfs_group_change_owner - change owner of an attribute group.
+ * @kobj:      The kobject containing the group.
+ * @grp:       The attribute group.
+ * @kuid:      new owner's kuid
+ * @kgid:      new owner's kgid
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_group_change_owner(struct kobject *kobj,
+                            const struct attribute_group *grp, kuid_t kuid,
+                            kgid_t kgid)
+{
+       struct kernfs_node *grp_kn;
+       int error;
+       struct iattr newattrs = {
+               .ia_valid = ATTR_UID | ATTR_GID,
+               .ia_uid = kuid,
+               .ia_gid = kgid,
+       };
+
+       if (!kobj->state_in_sysfs)
+               return -EINVAL;
+
+       if (grp->name) {
+               grp_kn = kernfs_find_and_get(kobj->sd, grp->name);
+       } else {
+               kernfs_get(kobj->sd);
+               grp_kn = kobj->sd;
+       }
+       if (!grp_kn)
+               return -ENOENT;
+
+       error = kernfs_setattr(grp_kn, &newattrs);
+       if (!error)
+               error = sysfs_group_attrs_change_owner(grp_kn, grp, &newattrs);
+
+       kernfs_put(grp_kn);
+
+       return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_group_change_owner);
+
+/**
+ * sysfs_groups_change_owner - change owner of a set of attribute groups.
+ * @kobj:      The kobject containing the groups.
+ * @groups:    The attribute groups.
+ * @kuid:      new owner's kuid
+ * @kgid:      new owner's kgid
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_groups_change_owner(struct kobject *kobj,
+                             const struct attribute_group **groups,
+                             kuid_t kuid, kgid_t kgid)
+{
+       int error = 0, i;
+
+       if (!kobj->state_in_sysfs)
+               return -EINVAL;
+
+       if (!groups)
+               return 0;
+
+       for (i = 0; groups[i]; i++) {
+               error = sysfs_group_change_owner(kobj, groups[i], kuid, kgid);
+               if (error)
+                       break;
+       }
+
+       return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_groups_change_owner);

diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 7e15ebf..3fcaabd 100644 (file)
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -314,6 +314,12 @@ int sysfs_file_change_owner(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);
+int sysfs_groups_change_owner(struct kobject *kobj,
+                             const struct attribute_group **groups,
+                             kuid_t kuid, kgid_t kgid);
+int sysfs_group_change_owner(struct kobject *kobj,
+                            const struct attribute_group *groups, kuid_t kuid,
+                            kgid_t kgid);
 
 #else /* CONFIG_SYSFS */
 
@@ -542,6 +548,20 @@ static inline int sysfs_link_change_owner(struct kobject *kobj,
        return 0;
 }
 
+static inline int sysfs_groups_change_owner(struct kobject *kobj,
+                         const struct attribute_group **groups,
+                         kuid_t kuid, kgid_t kgid)
+{
+       return 0;
+}
+
+static inline int sysfs_group_change_owner(struct kobject *kobj,
+                        const struct attribute_group **groups,
+                        kuid_t kuid, kgid_t kgid)
+{
+       return 0;
+}
+
 #endif /* CONFIG_SYSFS */
 
 static inline int __must_check sysfs_create_file(struct kobject *kobj,