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Linux/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         bool new_sb;
 31 
 32         if (!(flags & MS_KERNMOUNT)) {
 33                 if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
 34                         return ERR_PTR(-EPERM);
 35 
 36                 if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
 37                         return ERR_PTR(-EPERM);
 38         }
 39 
 40         ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
 41         root = kernfs_mount_ns(fs_type, flags, sysfs_root, &new_sb, ns);
 42         if (IS_ERR(root) || !new_sb)
 43                 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
 44         return root;
 45 }
 46 
 47 static void sysfs_kill_sb(struct super_block *sb)
 48 {
 49         void *ns = (void *)kernfs_super_ns(sb);
 50 
 51         kernfs_kill_sb(sb);
 52         kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
 53 }
 54 
 55 static struct file_system_type sysfs_fs_type = {
 56         .name           = "sysfs",
 57         .mount          = sysfs_mount,
 58         .kill_sb        = sysfs_kill_sb,
 59         .fs_flags       = FS_USERNS_MOUNT,
 60 };
 61 
 62 int __init sysfs_init(void)
 63 {
 64         int err;
 65 
 66         sysfs_root = kernfs_create_root(NULL, NULL);
 67         if (IS_ERR(sysfs_root))
 68                 return PTR_ERR(sysfs_root);
 69 
 70         sysfs_root_kn = sysfs_root->kn;
 71 
 72         err = register_filesystem(&sysfs_fs_type);
 73         if (err) {
 74                 kernfs_destroy_root(sysfs_root);
 75                 return err;
 76         }
 77 
 78         return 0;
 79 }
 80 

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