fs/sysfs/mount.c

   1 /*
   2  * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
   3  *
   4  * Copyright (c) 2001-3 Patrick Mochel
   5  * Copyright (c) 2007 SUSE Linux Products GmbH
   6  * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   7  *
   8  * This file is released under the GPLv2.
   9  *
  10  * Please see Documentation/filesystems/sysfs.txt for more information.
  11  */
  12
  13 #define DEBUG
  14
  15 #include <linux/fs.h>
  16 #include <linux/mount.h>
  17 #include <linux/init.h>
  18 #include <linux/user_namespace.h>
  19
  20 #include "sysfs.h"
  21
  22 static struct kernfs_root *sysfs_root;
  23 struct kernfs_node *sysfs_root_kn;
  24
  25 static struct dentry *sysfs_mount(struct file_system_type *fs_type,
  26         int flags, const char *dev_name, void *data)
  27 {
  28         struct dentry *root;
  29         void *ns;
  30
  31         if (!(flags & MS_KERNMOUNT)) {
  32                 if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
  33                         return ERR_PTR(-EPERM);
  34
  35                 if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
  36                         return ERR_PTR(-EPERM);
  37         }
  38
  39         ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
  40         root = kernfs_mount_ns(fs_type, flags, sysfs_root, ns);
  41         if (IS_ERR(root))
  42                 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
  43         return root;
  44 }
  45
  46 static void sysfs_kill_sb(struct super_block *sb)
  47 {
  48         void *ns = (void *)kernfs_super_ns(sb);
  49
  50         kernfs_kill_sb(sb);
  51         kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
  52 }
  53
  54 static struct file_system_type sysfs_fs_type = {
  55         .name           = "sysfs",
  56         .mount          = sysfs_mount,
  57         .kill_sb        = sysfs_kill_sb,
  58         .fs_flags       = FS_USERNS_MOUNT,
  59 };
  60
  61 int __init sysfs_init(void)
  62 {
  63         int err;
  64
  65         sysfs_root = kernfs_create_root(NULL, NULL);
  66         if (IS_ERR(sysfs_root))
  67                 return PTR_ERR(sysfs_root);
  68
  69         sysfs_root_kn = sysfs_root->kn;
  70
  71         err = register_filesystem(&sysfs_fs_type);
  72         if (err) {
  73                 kernfs_destroy_root(sysfs_root);
  74                 return err;
  75         }
  76
  77         return 0;
  78 }