fs/kernfs/inode.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * fs/kernfs/inode.c - kernfs inode implementation
   4  *
   5  * Copyright (c) 2001-3 Patrick Mochel
   6  * Copyright (c) 2007 SUSE Linux Products GmbH
   7  * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
   8  */
   9
  10 #include <linux/pagemap.h>
  11 #include <linux/backing-dev.h>
  12 #include <linux/capability.h>
  13 #include <linux/errno.h>
  14 #include <linux/slab.h>
  15 #include <linux/xattr.h>
  16 #include <linux/security.h>
  17
  18 #include "kernfs-internal.h"
  19
  20 static const struct address_space_operations kernfs_aops = {
  21         .readpage       = simple_readpage,
  22         .write_begin    = simple_write_begin,
  23         .write_end      = simple_write_end,
  24 };
  25
  26 static const struct inode_operations kernfs_iops = {
  27         .permission     = kernfs_iop_permission,
  28         .setattr        = kernfs_iop_setattr,
  29         .getattr        = kernfs_iop_getattr,
  30         .listxattr      = kernfs_iop_listxattr,
  31 };
  32
  33 static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc)
  34 {
  35         static DEFINE_MUTEX(iattr_mutex);
  36         struct kernfs_iattrs *ret;
  37
  38         mutex_lock(&iattr_mutex);
  39
  40         if (kn->iattr || !alloc)
  41                 goto out_unlock;
  42
  43         kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
  44         if (!kn->iattr)
  45                 goto out_unlock;
  46
  47         /* assign default attributes */
  48         kn->iattr->ia_uid = GLOBAL_ROOT_UID;
  49         kn->iattr->ia_gid = GLOBAL_ROOT_GID;
  50
  51         ktime_get_real_ts64(&kn->iattr->ia_atime);
  52         kn->iattr->ia_mtime = kn->iattr->ia_atime;
  53         kn->iattr->ia_ctime = kn->iattr->ia_atime;
  54
  55         simple_xattrs_init(&kn->iattr->xattrs);
  56         atomic_set(&kn->iattr->nr_user_xattrs, 0);
  57         atomic_set(&kn->iattr->user_xattr_size, 0);
  58 out_unlock:
  59         ret = kn->iattr;
  60         mutex_unlock(&iattr_mutex);
  61         return ret;
  62 }
  63
  64 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
  65 {
  66         return __kernfs_iattrs(kn, 1);
  67 }
  68
  69 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
  70 {
  71         return __kernfs_iattrs(kn, 0);
  72 }
  73
  74 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
  75 {
  76         struct kernfs_iattrs *attrs;
  77         unsigned int ia_valid = iattr->ia_valid;
  78
  79         attrs = kernfs_iattrs(kn);
  80         if (!attrs)
  81                 return -ENOMEM;
  82
  83         if (ia_valid & ATTR_UID)
  84                 attrs->ia_uid = iattr->ia_uid;
  85         if (ia_valid & ATTR_GID)
  86                 attrs->ia_gid = iattr->ia_gid;
  87         if (ia_valid & ATTR_ATIME)
  88                 attrs->ia_atime = iattr->ia_atime;
  89         if (ia_valid & ATTR_MTIME)
  90                 attrs->ia_mtime = iattr->ia_mtime;
  91         if (ia_valid & ATTR_CTIME)
  92                 attrs->ia_ctime = iattr->ia_ctime;
  93         if (ia_valid & ATTR_MODE)
  94                 kn->mode = iattr->ia_mode;
  95         return 0;
  96 }
  97
  98 /**
  99  * kernfs_setattr - set iattr on a node
 100  * @kn: target node
 101  * @iattr: iattr to set
 102  *
 103  * Returns 0 on success, -errno on failure.
 104  */
 105 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 106 {
 107         int ret;
 108
 109         mutex_lock(&kernfs_mutex);
 110         ret = __kernfs_setattr(kn, iattr);
 111         mutex_unlock(&kernfs_mutex);
 112         return ret;
 113 }
 114
 115 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
 116 {
 117         struct inode *inode = d_inode(dentry);
 118         struct kernfs_node *kn = inode->i_private;
 119         int error;
 120
 121         if (!kn)
 122                 return -EINVAL;
 123
 124         mutex_lock(&kernfs_mutex);
 125         error = setattr_prepare(dentry, iattr);
 126         if (error)
 127                 goto out;
 128
 129         error = __kernfs_setattr(kn, iattr);
 130         if (error)
 131                 goto out;
 132
 133         /* this ignores size changes */
 134         setattr_copy(inode, iattr);
 135
 136 out:
 137         mutex_unlock(&kernfs_mutex);
 138         return error;
 139 }
 140
 141 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
 142 {
 143         struct kernfs_node *kn = kernfs_dentry_node(dentry);
 144         struct kernfs_iattrs *attrs;
 145
 146         attrs = kernfs_iattrs(kn);
 147         if (!attrs)
 148                 return -ENOMEM;
 149
 150         return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
 151 }
 152
 153 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
 154 {
 155         inode->i_mode = mode;
 156         inode->i_atime = inode->i_mtime =
 157                 inode->i_ctime = current_time(inode);
 158 }
 159
 160 static inline void set_inode_attr(struct inode *inode,
 161                                   struct kernfs_iattrs *attrs)
 162 {
 163         inode->i_uid = attrs->ia_uid;
 164         inode->i_gid = attrs->ia_gid;
 165         inode->i_atime = attrs->ia_atime;
 166         inode->i_mtime = attrs->ia_mtime;
 167         inode->i_ctime = attrs->ia_ctime;
 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 = kernfs_gen(kn);
 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, kernfs_ino(kn));
 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, NULL);
 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 int kernfs_vfs_user_xattr_add(struct kernfs_node *kn,
 333                                      const char *full_name,
 334                                      struct simple_xattrs *xattrs,
 335                                      const void *value, size_t size, int flags)
 336 {
 337         atomic_t *sz = &kn->iattr->user_xattr_size;
 338         atomic_t *nr = &kn->iattr->nr_user_xattrs;
 339         ssize_t removed_size;
 340         int ret;
 341
 342         if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) {
 343                 ret = -ENOSPC;
 344                 goto dec_count_out;
 345         }
 346
 347         if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) {
 348                 ret = -ENOSPC;
 349                 goto dec_size_out;
 350         }
 351
 352         ret = simple_xattr_set(xattrs, full_name, value, size, flags,
 353                                &removed_size);
 354
 355         if (!ret && removed_size >= 0)
 356                 size = removed_size;
 357         else if (!ret)
 358                 return 0;
 359 dec_size_out:
 360         atomic_sub(size, sz);
 361 dec_count_out:
 362         atomic_dec(nr);
 363         return ret;
 364 }
 365
 366 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn,
 367                                     const char *full_name,
 368                                     struct simple_xattrs *xattrs,
 369                                     const void *value, size_t size, int flags)
 370 {
 371         atomic_t *sz = &kn->iattr->user_xattr_size;
 372         atomic_t *nr = &kn->iattr->nr_user_xattrs;
 373         ssize_t removed_size;
 374         int ret;
 375
 376         ret = simple_xattr_set(xattrs, full_name, value, size, flags,
 377                                &removed_size);
 378
 379         if (removed_size >= 0) {
 380                 atomic_sub(removed_size, sz);
 381                 atomic_dec(nr);
 382         }
 383
 384         return ret;
 385 }
 386
 387 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,
 388                                      struct dentry *unused, struct inode *inode,
 389                                      const char *suffix, const void *value,
 390                                      size_t size, int flags)
 391 {
 392         const char *full_name = xattr_full_name(handler, suffix);
 393         struct kernfs_node *kn = inode->i_private;
 394         struct kernfs_iattrs *attrs;
 395
 396         if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR))
 397                 return -EOPNOTSUPP;
 398
 399         attrs = kernfs_iattrs(kn);
 400         if (!attrs)
 401                 return -ENOMEM;
 402
 403         if (value)
 404                 return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs,
 405                                                  value, size, flags);
 406         else
 407                 return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs,
 408                                                 value, size, flags);
 409
 410 }
 411
 412 static const struct xattr_handler kernfs_trusted_xattr_handler = {
 413         .prefix = XATTR_TRUSTED_PREFIX,
 414         .get = kernfs_vfs_xattr_get,
 415         .set = kernfs_vfs_xattr_set,
 416 };
 417
 418 static const struct xattr_handler kernfs_security_xattr_handler = {
 419         .prefix = XATTR_SECURITY_PREFIX,
 420         .get = kernfs_vfs_xattr_get,
 421         .set = kernfs_vfs_xattr_set,
 422 };
 423
 424 static const struct xattr_handler kernfs_user_xattr_handler = {
 425         .prefix = XATTR_USER_PREFIX,
 426         .get = kernfs_vfs_xattr_get,
 427         .set = kernfs_vfs_user_xattr_set,
 428 };
 429
 430 const struct xattr_handler *kernfs_xattr_handlers[] = {
 431         &kernfs_trusted_xattr_handler,
 432         &kernfs_security_xattr_handler,
 433         &kernfs_user_xattr_handler,
 434         NULL
 435 };