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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/magic.h>
 17 #include <linux/mount.h>
 18 #include <linux/init.h>
 19 #include <linux/user_namespace.h>
 20 
 21 #include "sysfs.h"
 22 
 23 static struct kernfs_root *sysfs_root;
 24 struct kernfs_node *sysfs_root_kn;
 25 
 26 static struct dentry *sysfs_mount(struct file_system_type *fs_type,
 27         int flags, const char *dev_name, void *data)
 28 {
 29         struct dentry *root;
 30         void *ns;
 31         bool new_sb;
 32 
 33         if (!(flags & MS_KERNMOUNT)) {
 34                 if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
 35                         return ERR_PTR(-EPERM);
 36         }
 37 
 38         ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
 39         root = kernfs_mount_ns(fs_type, flags, sysfs_root,
 40                                 SYSFS_MAGIC, &new_sb, ns);
 41         if (IS_ERR(root) || !new_sb)
 42                 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
 43         else if (new_sb)
 44                 /* Userspace would break if executables appear on sysfs */
 45                 root->d_sb->s_iflags |= SB_I_NOEXEC;
 46 
 47         return root;
 48 }
 49 
 50 static void sysfs_kill_sb(struct super_block *sb)
 51 {
 52         void *ns = (void *)kernfs_super_ns(sb);
 53 
 54         kernfs_kill_sb(sb);
 55         kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
 56 }
 57 
 58 static struct file_system_type sysfs_fs_type = {
 59         .name           = "sysfs",
 60         .mount          = sysfs_mount,
 61         .kill_sb        = sysfs_kill_sb,
 62         .fs_flags       = FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
 63 };
 64 
 65 int __init sysfs_init(void)
 66 {
 67         int err;
 68 
 69         sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
 70                                         NULL);
 71         if (IS_ERR(sysfs_root))
 72                 return PTR_ERR(sysfs_root);
 73 
 74         sysfs_root_kn = sysfs_root->kn;
 75 
 76         err = register_filesystem(&sysfs_fs_type);
 77         if (err) {
 78                 kernfs_destroy_root(sysfs_root);
 79                 return err;
 80         }
 81 
 82         return 0;
 83 }
 84 

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