fs/kernfs/inode.c

   1 /*
   2  * fs/kernfs/inode.c - kernfs inode implementation
   3  *
   4  * Copyright (c) 2001-3 Patrick Mochel
   5  * Copyright (c) 2007 SUSE Linux Products GmbH
   6  * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
   7  *
   8  * This file is released under the GPLv2.
   9  */
  10
  11 #include <linux/pagemap.h>
  12 #include <linux/backing-dev.h>
  13 #include <linux/capability.h>
  14 #include <linux/errno.h>
  15 #include <linux/slab.h>
  16 #include <linux/xattr.h>
  17 #include <linux/security.h>
  18
  19 #include "kernfs-internal.h"
  20
  21 static const struct address_space_operations kernfs_aops = {
  22         .readpage       = simple_readpage,
  23         .write_begin    = simple_write_begin,
  24         .write_end      = simple_write_end,
  25 };
  26
  27 static const struct inode_operations kernfs_iops = {
  28         .permission     = kernfs_iop_permission,
  29         .setattr        = kernfs_iop_setattr,
  30         .getattr        = kernfs_iop_getattr,
  31         .listxattr      = kernfs_iop_listxattr,
  32 };
  33
  34 static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc)
  35 {
  36         static DEFINE_MUTEX(iattr_mutex);
  37         struct kernfs_iattrs *ret;
  38
  39         mutex_lock(&iattr_mutex);
  40
  41         if (kn->iattr || !alloc)
  42                 goto out_unlock;
  43
  44         kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
  45         if (!kn->iattr)
  46                 goto out_unlock;
  47
  48         /* assign default attributes */
  49         kn->iattr->ia_uid = GLOBAL_ROOT_UID;
  50         kn->iattr->ia_gid = GLOBAL_ROOT_GID;
  51
  52         ktime_get_real_ts64(&kn->iattr->ia_atime);
  53         kn->iattr->ia_mtime = kn->iattr->ia_atime;
  54         kn->iattr->ia_ctime = kn->iattr->ia_atime;
  55
  56         simple_xattrs_init(&kn->iattr->xattrs);
  57 out_unlock:
  58         ret = kn->iattr;
  59         mutex_unlock(&iattr_mutex);
  60         return ret;
  61 }
  62
  63 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
  64 {
  65         return __kernfs_iattrs(kn, 1);
  66 }
  67
  68 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
  69 {
  70         return __kernfs_iattrs(kn, 0);
  71 }
  72
  73 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
  74 {
  75         struct kernfs_iattrs *attrs;
  76         unsigned int ia_valid = iattr->ia_valid;
  77
  78         attrs = kernfs_iattrs(kn);
  79         if (!attrs)
  80                 return -ENOMEM;
  81
  82         if (ia_valid & ATTR_UID)
  83                 attrs->ia_uid = iattr->ia_uid;
  84         if (ia_valid & ATTR_GID)
  85                 attrs->ia_gid = iattr->ia_gid;
  86         if (ia_valid & ATTR_ATIME)
  87                 attrs->ia_atime = iattr->ia_atime;
  88         if (ia_valid & ATTR_MTIME)
  89                 attrs->ia_mtime = iattr->ia_mtime;
  90         if (ia_valid & ATTR_CTIME)
  91                 attrs->ia_ctime = iattr->ia_ctime;
  92         if (ia_valid & ATTR_MODE)
  93                 kn->mode = iattr->ia_mode;
  94         return 0;
  95 }
  96
  97 /**
  98  * kernfs_setattr - set iattr on a node
  99  * @kn: target node
 100  * @iattr: iattr to set
 101  *
 102  * Returns 0 on success, -errno on failure.
 103  */
 104 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 105 {
 106         int ret;
 107
 108         mutex_lock(&kernfs_mutex);
 109         ret = __kernfs_setattr(kn, iattr);
 110         mutex_unlock(&kernfs_mutex);
 111         return ret;
 112 }
 113
 114 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
 115 {
 116         struct inode *inode = d_inode(dentry);
 117         struct kernfs_node *kn = inode->i_private;
 118         int error;
 119
 120         if (!kn)
 121                 return -EINVAL;
 122
 123         mutex_lock(&kernfs_mutex);
 124         error = setattr_prepare(dentry, iattr);
 125         if (error)
 126                 goto out;
 127
 128         error = __kernfs_setattr(kn, iattr);
 129         if (error)
 130                 goto out;
 131
 132         /* this ignores size changes */
 133         setattr_copy(inode, iattr);
 134
 135 out:
 136         mutex_unlock(&kernfs_mutex);
 137         return error;
 138 }
 139
 140 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
 141 {
 142         struct kernfs_node *kn = kernfs_dentry_node(dentry);
 143         struct kernfs_iattrs *attrs;
 144
 145         attrs = kernfs_iattrs(kn);
 146         if (!attrs)
 147                 return -ENOMEM;
 148
 149         return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
 150 }
 151
 152 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
 153 {
 154         inode->i_mode = mode;
 155         inode->i_atime = inode->i_mtime =
 156                 inode->i_ctime = current_time(inode);
 157 }
 158
 159 static inline void set_inode_attr(struct inode *inode,
 160                                   struct kernfs_iattrs *attrs)
 161 {
 162         struct super_block *sb = inode->i_sb;
 163         inode->i_uid = attrs->ia_uid;
 164         inode->i_gid = attrs->ia_gid;
 165         inode->i_atime = timespec64_trunc(attrs->ia_atime, sb->s_time_gran);
 166         inode->i_mtime = timespec64_trunc(attrs->ia_mtime, sb->s_time_gran);
 167         inode->i_ctime = timespec64_trunc(attrs->ia_ctime, sb->s_time_gran);
 168 }
 169
 170 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
 171 {
 172         struct kernfs_iattrs *attrs = kn->iattr;
 173
 174         inode->i_mode = kn->mode;
 175         if (attrs)
 176                 /*
 177                  * kernfs_node has non-default attributes get them from
 178                  * persistent copy in kernfs_node.
 179                  */
 180                 set_inode_attr(inode, attrs);
 181
 182         if (kernfs_type(kn) == KERNFS_DIR)
 183                 set_nlink(inode, kn->dir.subdirs + 2);
 184 }
 185
 186 int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
 187                        u32 request_mask, unsigned int query_flags)
 188 {
 189         struct inode *inode = d_inode(path->dentry);
 190         struct kernfs_node *kn = inode->i_private;
 191
 192         mutex_lock(&kernfs_mutex);
 193         kernfs_refresh_inode(kn, inode);
 194         mutex_unlock(&kernfs_mutex);
 195
 196         generic_fillattr(inode, stat);
 197         return 0;
 198 }
 199
 200 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
 201 {
 202         kernfs_get(kn);
 203         inode->i_private = kn;
 204         inode->i_mapping->a_ops = &kernfs_aops;
 205         inode->i_op = &kernfs_iops;
 206         inode->i_generation = kn->id.generation;
 207
 208         set_default_inode_attr(inode, kn->mode);
 209         kernfs_refresh_inode(kn, inode);
 210
 211         /* initialize inode according to type */
 212         switch (kernfs_type(kn)) {
 213         case KERNFS_DIR:
 214                 inode->i_op = &kernfs_dir_iops;
 215                 inode->i_fop = &kernfs_dir_fops;
 216                 if (kn->flags & KERNFS_EMPTY_DIR)
 217                         make_empty_dir_inode(inode);
 218                 break;
 219         case KERNFS_FILE:
 220                 inode->i_size = kn->attr.size;
 221                 inode->i_fop = &kernfs_file_fops;
 222                 break;
 223         case KERNFS_LINK:
 224                 inode->i_op = &kernfs_symlink_iops;
 225                 break;
 226         default:
 227                 BUG();
 228         }
 229
 230         unlock_new_inode(inode);
 231 }
 232
 233 /**
 234  *      kernfs_get_inode - get inode for kernfs_node
 235  *      @sb: super block
 236  *      @kn: kernfs_node to allocate inode for
 237  *
 238  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
 239  *      allocated and basics are initialized.  New inode is returned
 240  *      locked.
 241  *
 242  *      LOCKING:
 243  *      Kernel thread context (may sleep).
 244  *
 245  *      RETURNS:
 246  *      Pointer to allocated inode on success, NULL on failure.
 247  */
 248 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 249 {
 250         struct inode *inode;
 251
 252         inode = iget_locked(sb, kn->id.ino);
 253         if (inode && (inode->i_state & I_NEW))
 254                 kernfs_init_inode(kn, inode);
 255
 256         return inode;
 257 }
 258
 259 /*
 260  * The kernfs_node serves as both an inode and a directory entry for
 261  * kernfs.  To prevent the kernfs inode numbers from being freed
 262  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
 263  * super_operations.evict_inode() implementation is needed to drop that
 264  * reference upon inode destruction.
 265  */
 266 void kernfs_evict_inode(struct inode *inode)
 267 {
 268         struct kernfs_node *kn = inode->i_private;
 269
 270         truncate_inode_pages_final(&inode->i_data);
 271         clear_inode(inode);
 272         kernfs_put(kn);
 273 }
 274
 275 int kernfs_iop_permission(struct inode *inode, int mask)
 276 {
 277         struct kernfs_node *kn;
 278
 279         if (mask & MAY_NOT_BLOCK)
 280                 return -ECHILD;
 281
 282         kn = inode->i_private;
 283
 284         mutex_lock(&kernfs_mutex);
 285         kernfs_refresh_inode(kn, inode);
 286         mutex_unlock(&kernfs_mutex);
 287
 288         return generic_permission(inode, mask);
 289 }
 290
 291 int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
 292                      void *value, size_t size)
 293 {
 294         struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
 295         if (!attrs)
 296                 return -ENODATA;
 297
 298         return simple_xattr_get(&attrs->xattrs, name, value, size);
 299 }
 300
 301 int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
 302                      const void *value, size_t size, int flags)
 303 {
 304         struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
 305         if (!attrs)
 306                 return -ENOMEM;
 307
 308         return simple_xattr_set(&attrs->xattrs, name, value, size, flags);
 309 }
 310
 311 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
 312                                 struct dentry *unused, struct inode *inode,
 313                                 const char *suffix, void *value, size_t size)
 314 {
 315         const char *name = xattr_full_name(handler, suffix);
 316         struct kernfs_node *kn = inode->i_private;
 317
 318         return kernfs_xattr_get(kn, name, value, size);
 319 }
 320
 321 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
 322                                 struct dentry *unused, struct inode *inode,
 323                                 const char *suffix, const void *value,
 324                                 size_t size, int flags)
 325 {
 326         const char *name = xattr_full_name(handler, suffix);
 327         struct kernfs_node *kn = inode->i_private;
 328
 329         return kernfs_xattr_set(kn, name, value, size, flags);
 330 }
 331
 332 static const struct xattr_handler kernfs_trusted_xattr_handler = {
 333         .prefix = XATTR_TRUSTED_PREFIX,
 334         .get = kernfs_vfs_xattr_get,
 335         .set = kernfs_vfs_xattr_set,
 336 };
 337
 338 static const struct xattr_handler kernfs_security_xattr_handler = {
 339         .prefix = XATTR_SECURITY_PREFIX,
 340         .get = kernfs_vfs_xattr_get,
 341         .set = kernfs_vfs_xattr_set,
 342 };
 343
 344 const struct xattr_handler *kernfs_xattr_handlers[] = {
 345         &kernfs_trusted_xattr_handler,
 346         &kernfs_security_xattr_handler,
 347         NULL
 348 };