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.rst 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         if (WARN_ON(!kobj))
  47                 return -EINVAL;
  48
  49         if (kobj->parent)
  50                 parent = kobj->parent->sd;
  51         else
  52                 parent = sysfs_root_kn;
  53
  54         if (!parent)
  55                 return -ENOENT;
  56
  57         kobject_get_ownership(kobj, &uid, &gid);
  58
  59         kn = kernfs_create_dir_ns(parent, kobject_name(kobj),
  60                                   S_IRWXU | S_IRUGO | S_IXUGO, uid, gid,
  61                                   kobj, ns);
  62         if (IS_ERR(kn)) {
  63                 if (PTR_ERR(kn) == -EEXIST)
  64                         sysfs_warn_dup(parent, kobject_name(kobj));
  65                 return PTR_ERR(kn);
  66         }
  67
  68         kobj->sd = kn;
  69         return 0;
  70 }
  71
  72 /**
  73  *      sysfs_remove_dir - remove an object's directory.
  74  *      @kobj:  object.
  75  *
  76  *      The only thing special about this is that we remove any files in
  77  *      the directory before we remove the directory, and we've inlined
  78  *      what used to be sysfs_rmdir() below, instead of calling separately.
  79  */
  80 void sysfs_remove_dir(struct kobject *kobj)
  81 {
  82         struct kernfs_node *kn = kobj->sd;
  83
  84         /*
  85          * In general, kboject owner is responsible for ensuring removal
  86          * doesn't race with other operations and sysfs doesn't provide any
  87          * protection; however, when @kobj is used as a symlink target, the
  88          * symlinking entity usually doesn't own @kobj and thus has no
  89          * control over removal.  @kobj->sd may be removed anytime
  90          * and symlink code may end up dereferencing an already freed node.
  91          *
  92          * sysfs_symlink_target_lock synchronizes @kobj->sd
  93          * disassociation against symlink operations so that symlink code
  94          * can safely dereference @kobj->sd.
  95          */
  96         spin_lock(&sysfs_symlink_target_lock);
  97         kobj->sd = NULL;
  98         spin_unlock(&sysfs_symlink_target_lock);
  99
 100         if (kn) {
 101                 WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
 102                 kernfs_remove(kn);
 103         }
 104 }
 105
 106 int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
 107                         const void *new_ns)
 108 {
 109         struct kernfs_node *parent;
 110         int ret;
 111
 112         parent = kernfs_get_parent(kobj->sd);
 113         ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
 114         kernfs_put(parent);
 115         return ret;
 116 }
 117
 118 int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
 119                       const void *new_ns)
 120 {
 121         struct kernfs_node *kn = kobj->sd;
 122         struct kernfs_node *new_parent;
 123
 124         new_parent = new_parent_kobj && new_parent_kobj->sd ?
 125                 new_parent_kobj->sd : sysfs_root_kn;
 126
 127         return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
 128 }
 129
 130 /**
 131  * sysfs_create_mount_point - create an always empty directory
 132  * @parent_kobj:  kobject that will contain this always empty directory
 133  * @name: The name of the always empty directory to add
 134  */
 135 int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
 136 {
 137         struct kernfs_node *kn, *parent = parent_kobj->sd;
 138
 139         kn = kernfs_create_empty_dir(parent, name);
 140         if (IS_ERR(kn)) {
 141                 if (PTR_ERR(kn) == -EEXIST)
 142                         sysfs_warn_dup(parent, name);
 143                 return PTR_ERR(kn);
 144         }
 145
 146         return 0;
 147 }
 148 EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
 149
 150 /**
 151  *      sysfs_remove_mount_point - remove an always empty directory.
 152  *      @parent_kobj: kobject that will contain this always empty directory
 153  *      @name: The name of the always empty directory to remove
 154  *
 155  */
 156 void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
 157 {
 158         struct kernfs_node *parent = parent_kobj->sd;
 159
 160         kernfs_remove_by_name_ns(parent, name, NULL);
 161 }
 162 EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);