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 user_namespace *mnt_userns, struct dentry *dentry,
 116                        struct iattr *iattr)
 117 {
 118         struct inode *inode = d_inode(dentry);
 119         struct kernfs_node *kn = inode->i_private;
 120         int error;
 121
 122         if (!kn)
 123                 return -EINVAL;
 124
 125         mutex_lock(&kernfs_mutex);
 126         error = setattr_prepare(&init_user_ns, dentry, iattr);
 127         if (error)
 128                 goto out;
 129
 130         error = __kernfs_setattr(kn, iattr);
 131         if (error)
 132                 goto out;
 133
 134         /* this ignores size changes */
 135         setattr_copy(&init_user_ns, inode, iattr);
 136
 137 out:
 138         mutex_unlock(&kernfs_mutex);
 139         return error;
 140 }
 141
 142 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
 143 {
 144         struct kernfs_node *kn = kernfs_dentry_node(dentry);
 145         struct kernfs_iattrs *attrs;
 146
 147         attrs = kernfs_iattrs(kn);
 148         if (!attrs)
 149                 return -ENOMEM;
 150
 151         return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
 152 }
 153
 154 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
 155 {
 156         inode->i_mode = mode;
 157         inode->i_atime = inode->i_mtime =
 158                 inode->i_ctime = current_time(inode);
 159 }
 160
 161 static inline void set_inode_attr(struct inode *inode,
 162                                   struct kernfs_iattrs *attrs)
 163 {
 164         inode->i_uid = attrs->ia_uid;
 165         inode->i_gid = attrs->ia_gid;
 166         inode->i_atime = attrs->ia_atime;
 167         inode->i_mtime = attrs->ia_mtime;
 168         inode->i_ctime = attrs->ia_ctime;
 169 }
 170
 171 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
 172 {
 173         struct kernfs_iattrs *attrs = kn->iattr;
 174
 175         inode->i_mode = kn->mode;
 176         if (attrs)
 177                 /*
 178                  * kernfs_node has non-default attributes get them from
 179                  * persistent copy in kernfs_node.
 180                  */
 181                 set_inode_attr(inode, attrs);
 182
 183         if (kernfs_type(kn) == KERNFS_DIR)
 184                 set_nlink(inode, kn->dir.subdirs + 2);
 185 }
 186
 187 int kernfs_iop_getattr(struct user_namespace *mnt_userns,
 188                        const struct path *path, struct kstat *stat,
 189                        u32 request_mask, unsigned int query_flags)
 190 {
 191         struct inode *inode = d_inode(path->dentry);
 192         struct kernfs_node *kn = inode->i_private;
 193
 194         mutex_lock(&kernfs_mutex);
 195         kernfs_refresh_inode(kn, inode);
 196         mutex_unlock(&kernfs_mutex);
 197
 198         generic_fillattr(&init_user_ns, inode, stat);
 199         return 0;
 200 }
 201
 202 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
 203 {
 204         kernfs_get(kn);
 205         inode->i_private = kn;
 206         inode->i_mapping->a_ops = &kernfs_aops;
 207         inode->i_op = &kernfs_iops;
 208         inode->i_generation = kernfs_gen(kn);
 209
 210         set_default_inode_attr(inode, kn->mode);
 211         kernfs_refresh_inode(kn, inode);
 212
 213         /* initialize inode according to type */
 214         switch (kernfs_type(kn)) {
 215         case KERNFS_DIR:
 216                 inode->i_op = &kernfs_dir_iops;
 217                 inode->i_fop = &kernfs_dir_fops;
 218                 if (kn->flags & KERNFS_EMPTY_DIR)
 219                         make_empty_dir_inode(inode);
 220                 break;
 221         case KERNFS_FILE:
 222                 inode->i_size = kn->attr.size;
 223                 inode->i_fop = &kernfs_file_fops;
 224                 break;
 225         case KERNFS_LINK:
 226                 inode->i_op = &kernfs_symlink_iops;
 227                 break;
 228         default:
 229                 BUG();
 230         }
 231
 232         unlock_new_inode(inode);
 233 }
 234
 235 /**
 236  *      kernfs_get_inode - get inode for kernfs_node
 237  *      @sb: super block
 238  *      @kn: kernfs_node to allocate inode for
 239  *
 240  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
 241  *      allocated and basics are initialized.  New inode is returned
 242  *      locked.
 243  *
 244  *      LOCKING:
 245  *      Kernel thread context (may sleep).
 246  *
 247  *      RETURNS:
 248  *      Pointer to allocated inode on success, NULL on failure.
 249  */
 250 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 251 {
 252         struct inode *inode;
 253
 254         inode = iget_locked(sb, kernfs_ino(kn));
 255         if (inode && (inode->i_state & I_NEW))
 256                 kernfs_init_inode(kn, inode);
 257
 258         return inode;
 259 }
 260
 261 /*
 262  * The kernfs_node serves as both an inode and a directory entry for
 263  * kernfs.  To prevent the kernfs inode numbers from being freed
 264  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
 265  * super_operations.evict_inode() implementation is needed to drop that
 266  * reference upon inode destruction.
 267  */
 268 void kernfs_evict_inode(struct inode *inode)
 269 {
 270         struct kernfs_node *kn = inode->i_private;
 271
 272         truncate_inode_pages_final(&inode->i_data);
 273         clear_inode(inode);
 274         kernfs_put(kn);
 275 }
 276
 277 int kernfs_iop_permission(struct user_namespace *mnt_userns,
 278                           struct inode *inode, int mask)
 279 {
 280         struct kernfs_node *kn;
 281
 282         if (mask & MAY_NOT_BLOCK)
 283                 return -ECHILD;
 284
 285         kn = inode->i_private;
 286
 287         mutex_lock(&kernfs_mutex);
 288         kernfs_refresh_inode(kn, inode);
 289         mutex_unlock(&kernfs_mutex);
 290
 291         return generic_permission(&init_user_ns, inode, mask);
 292 }
 293
 294 int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
 295                      void *value, size_t size)
 296 {
 297         struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
 298         if (!attrs)
 299                 return -ENODATA;
 300
 301         return simple_xattr_get(&attrs->xattrs, name, value, size);
 302 }
 303
 304 int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
 305                      const void *value, size_t size, int flags)
 306 {
 307         struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
 308         if (!attrs)
 309                 return -ENOMEM;
 310
 311         return simple_xattr_set(&attrs->xattrs, name, value, size, flags, NULL);
 312 }
 313
 314 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
 315                                 struct dentry *unused, struct inode *inode,
 316                                 const char *suffix, void *value, size_t size)
 317 {
 318         const char *name = xattr_full_name(handler, suffix);
 319         struct kernfs_node *kn = inode->i_private;
 320
 321         return kernfs_xattr_get(kn, name, value, size);
 322 }
 323
 324 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
 325                                 struct user_namespace *mnt_userns,
 326                                 struct dentry *unused, struct inode *inode,
 327                                 const char *suffix, const void *value,
 328                                 size_t size, int flags)
 329 {
 330         const char *name = xattr_full_name(handler, suffix);
 331         struct kernfs_node *kn = inode->i_private;
 332
 333         return kernfs_xattr_set(kn, name, value, size, flags);
 334 }
 335
 336 static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn,
 337                                      const char *full_name,
 338                                      struct simple_xattrs *xattrs,
 339                                      const void *value, size_t size, int flags)
 340 {
 341         atomic_t *sz = &kn->iattr->user_xattr_size;
 342         atomic_t *nr = &kn->iattr->nr_user_xattrs;
 343         ssize_t removed_size;
 344         int ret;
 345
 346         if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) {
 347                 ret = -ENOSPC;
 348                 goto dec_count_out;
 349         }
 350
 351         if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) {
 352                 ret = -ENOSPC;
 353                 goto dec_size_out;
 354         }
 355
 356         ret = simple_xattr_set(xattrs, full_name, value, size, flags,
 357                                &removed_size);
 358
 359         if (!ret && removed_size >= 0)
 360                 size = removed_size;
 361         else if (!ret)
 362                 return 0;
 363 dec_size_out:
 364         atomic_sub(size, sz);
 365 dec_count_out:
 366         atomic_dec(nr);
 367         return ret;
 368 }
 369
 370 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn,
 371                                     const char *full_name,
 372                                     struct simple_xattrs *xattrs,
 373                                     const void *value, size_t size, int flags)
 374 {
 375         atomic_t *sz = &kn->iattr->user_xattr_size;
 376         atomic_t *nr = &kn->iattr->nr_user_xattrs;
 377         ssize_t removed_size;
 378         int ret;
 379
 380         ret = simple_xattr_set(xattrs, full_name, value, size, flags,
 381                                &removed_size);
 382
 383         if (removed_size >= 0) {
 384                 atomic_sub(removed_size, sz);
 385                 atomic_dec(nr);
 386         }
 387
 388         return ret;
 389 }
 390
 391 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,
 392                                      struct user_namespace *mnt_userns,
 393                                      struct dentry *unused, struct inode *inode,
 394                                      const char *suffix, const void *value,
 395                                      size_t size, int flags)
 396 {
 397         const char *full_name = xattr_full_name(handler, suffix);
 398         struct kernfs_node *kn = inode->i_private;
 399         struct kernfs_iattrs *attrs;
 400
 401         if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR))
 402                 return -EOPNOTSUPP;
 403
 404         attrs = kernfs_iattrs(kn);
 405         if (!attrs)
 406                 return -ENOMEM;
 407
 408         if (value)
 409                 return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs,
 410                                                  value, size, flags);
 411         else
 412                 return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs,
 413                                                 value, size, flags);
 414
 415 }
 416
 417 static const struct xattr_handler kernfs_trusted_xattr_handler = {
 418         .prefix = XATTR_TRUSTED_PREFIX,
 419         .get = kernfs_vfs_xattr_get,
 420         .set = kernfs_vfs_xattr_set,
 421 };
 422
 423 static const struct xattr_handler kernfs_security_xattr_handler = {
 424         .prefix = XATTR_SECURITY_PREFIX,
 425         .get = kernfs_vfs_xattr_get,
 426         .set = kernfs_vfs_xattr_set,
 427 };
 428
 429 static const struct xattr_handler kernfs_user_xattr_handler = {
 430         .prefix = XATTR_USER_PREFIX,
 431         .get = kernfs_vfs_xattr_get,
 432         .set = kernfs_vfs_user_xattr_set,
 433 };
 434
 435 const struct xattr_handler *kernfs_xattr_handlers[] = {
 436         &kernfs_trusted_xattr_handler,
 437         &kernfs_security_xattr_handler,
 438         &kernfs_user_xattr_handler,
 439         NULL
 440 };