fs/sysfs/dir.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * fs/sysfs/dir.c - sysfs core and dir operation implementation
   4  *
   5  * Copyright (c) 2001-3 Patrick Mochel
   6  * Copyright (c) 2007 SUSE Linux Products GmbH
   7  * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   8  *
   9  * Please see Documentation/filesystems/sysfs.txt for more information.
  10  */
  11
  12 #define pr_fmt(fmt)     "sysfs: " fmt
  13
  14 #include <linux/fs.h>
  15 #include <linux/kobject.h>
  16 #include <linux/slab.h>
  17 #include "sysfs.h"
  18
  19 DEFINE_SPINLOCK(sysfs_symlink_target_lock);
  20
  21 void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
  22 {
  23         char *buf;
  24
  25         buf = kzalloc(PATH_MAX, GFP_KERNEL);
  26         if (buf)
  27                 kernfs_path(parent, buf, PATH_MAX);
  28
  29         pr_warn("cannot create duplicate filename '%s/%s'\n", buf, name);
  30         dump_stack();
  31
  32         kfree(buf);
  33 }
  34
  35 /**
  36  * sysfs_create_dir_ns - create a directory for an object with a namespace tag
  37  * @kobj: object we're creating directory for
  38  * @ns: the namespace tag to use
  39  */
  40 int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
  41 {
  42         struct kernfs_node *parent, *kn;
  43         kuid_t uid;
  44         kgid_t gid;
  45
  46         BUG_ON(!kobj);
  47
  48         if (kobj->parent)
  49                 parent = kobj->parent->sd;
  50         else
  51                 parent = sysfs_root_kn;
  52
  53         if (!parent)
  54                 return -ENOENT;
  55
  56         kobject_get_ownership(kobj, &uid, &gid);
  57
  58         kn = kernfs_create_dir_ns(parent, kobject_name(kobj),
  59                                   S_IRWXU | S_IRUGO | S_IXUGO, uid, gid,
  60                                   kobj, ns);
  61         if (IS_ERR(kn)) {
  62                 if (PTR_ERR(kn) == -EEXIST)
  63                         sysfs_warn_dup(parent, kobject_name(kobj));
  64                 return PTR_ERR(kn);
  65         }
  66
  67         kobj->sd = kn;
  68         return 0;
  69 }
  70
  71 /**
  72  *      sysfs_remove_dir - remove an object's directory.
  73  *      @kobj:  object.
  74  *
  75  *      The only thing special about this is that we remove any files in
  76  *      the directory before we remove the directory, and we've inlined
  77  *      what used to be sysfs_rmdir() below, instead of calling separately.
  78  */
  79 void sysfs_remove_dir(struct kobject *kobj)
  80 {
  81         struct kernfs_node *kn = kobj->sd;
  82
  83         /*
  84          * In general, kboject owner is responsible for ensuring removal
  85          * doesn't race with other operations and sysfs doesn't provide any
  86          * protection; however, when @kobj is used as a symlink target, the
  87          * symlinking entity usually doesn't own @kobj and thus has no
  88          * control over removal.  @kobj->sd may be removed anytime
  89          * and symlink code may end up dereferencing an already freed node.
  90          *
  91          * sysfs_symlink_target_lock synchronizes @kobj->sd
  92          * disassociation against symlink operations so that symlink code
  93          * can safely dereference @kobj->sd.
  94          */
  95         spin_lock(&sysfs_symlink_target_lock);
  96         kobj->sd = NULL;
  97         spin_unlock(&sysfs_symlink_target_lock);
  98
  99         if (kn) {
 100                 WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
 101                 kernfs_remove(kn);
 102         }
 103 }
 104
 105 int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
 106                         const void *new_ns)
 107 {
 108         struct kernfs_node *parent;
 109         int ret;
 110
 111         parent = kernfs_get_parent(kobj->sd);
 112         ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
 113         kernfs_put(parent);
 114         return ret;
 115 }
 116
 117 int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
 118                       const void *new_ns)
 119 {
 120         struct kernfs_node *kn = kobj->sd;
 121         struct kernfs_node *new_parent;
 122
 123         new_parent = new_parent_kobj && new_parent_kobj->sd ?
 124                 new_parent_kobj->sd : sysfs_root_kn;
 125
 126         return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
 127 }
 128
 129 /**
 130  * sysfs_create_mount_point - create an always empty directory
 131  * @parent_kobj:  kobject that will contain this always empty directory
 132  * @name: The name of the always empty directory to add
 133  */
 134 int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
 135 {
 136         struct kernfs_node *kn, *parent = parent_kobj->sd;
 137
 138         kn = kernfs_create_empty_dir(parent, name);
 139         if (IS_ERR(kn)) {
 140                 if (PTR_ERR(kn) == -EEXIST)
 141                         sysfs_warn_dup(parent, name);
 142                 return PTR_ERR(kn);
 143         }
 144
 145         return 0;
 146 }
 147 EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
 148
 149 /**
 150  *      sysfs_remove_mount_point - remove an always empty directory.
 151  *      @parent_kobj: kobject that will contain this always empty directory
 152  *      @name: The name of the always empty directory to remove
 153  *
 154  */
 155 void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
 156 {
 157         struct kernfs_node *parent = parent_kobj->sd;
 158
 159         kernfs_remove_by_name_ns(parent, name, NULL);
 160 }
 161 EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);