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 struct backing_dev_info kernfs_bdi = {
  28         .name           = "kernfs",
  29         .ra_pages       = 0,    /* No readahead */
  30         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  31 };
  32
  33 static const struct inode_operations kernfs_iops = {
  34         .permission     = kernfs_iop_permission,
  35         .setattr        = kernfs_iop_setattr,
  36         .getattr        = kernfs_iop_getattr,
  37         .setxattr       = kernfs_iop_setxattr,
  38         .removexattr    = kernfs_iop_removexattr,
  39         .getxattr       = kernfs_iop_getxattr,
  40         .listxattr      = kernfs_iop_listxattr,
  41 };
  42
  43 void __init kernfs_inode_init(void)
  44 {
  45         if (bdi_init(&kernfs_bdi))
  46                 panic("failed to init kernfs_bdi");
  47 }
  48
  49 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
  50 {
  51         static DEFINE_MUTEX(iattr_mutex);
  52         struct kernfs_iattrs *ret;
  53         struct iattr *iattrs;
  54
  55         mutex_lock(&iattr_mutex);
  56
  57         if (kn->iattr)
  58                 goto out_unlock;
  59
  60         kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
  61         if (!kn->iattr)
  62                 goto out_unlock;
  63         iattrs = &kn->iattr->ia_iattr;
  64
  65         /* assign default attributes */
  66         iattrs->ia_mode = kn->mode;
  67         iattrs->ia_uid = GLOBAL_ROOT_UID;
  68         iattrs->ia_gid = GLOBAL_ROOT_GID;
  69         iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
  70
  71         simple_xattrs_init(&kn->iattr->xattrs);
  72 out_unlock:
  73         ret = kn->iattr;
  74         mutex_unlock(&iattr_mutex);
  75         return ret;
  76 }
  77
  78 static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
  79 {
  80         struct kernfs_iattrs *attrs;
  81         struct iattr *iattrs;
  82         unsigned int ia_valid = iattr->ia_valid;
  83
  84         attrs = kernfs_iattrs(kn);
  85         if (!attrs)
  86                 return -ENOMEM;
  87
  88         iattrs = &attrs->ia_iattr;
  89
  90         if (ia_valid & ATTR_UID)
  91                 iattrs->ia_uid = iattr->ia_uid;
  92         if (ia_valid & ATTR_GID)
  93                 iattrs->ia_gid = iattr->ia_gid;
  94         if (ia_valid & ATTR_ATIME)
  95                 iattrs->ia_atime = iattr->ia_atime;
  96         if (ia_valid & ATTR_MTIME)
  97                 iattrs->ia_mtime = iattr->ia_mtime;
  98         if (ia_valid & ATTR_CTIME)
  99                 iattrs->ia_ctime = iattr->ia_ctime;
 100         if (ia_valid & ATTR_MODE) {
 101                 umode_t mode = iattr->ia_mode;
 102                 iattrs->ia_mode = kn->mode = mode;
 103         }
 104         return 0;
 105 }
 106
 107 /**
 108  * kernfs_setattr - set iattr on a node
 109  * @kn: target node
 110  * @iattr: iattr to set
 111  *
 112  * Returns 0 on success, -errno on failure.
 113  */
 114 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 115 {
 116         int ret;
 117
 118         mutex_lock(&kernfs_mutex);
 119         ret = __kernfs_setattr(kn, iattr);
 120         mutex_unlock(&kernfs_mutex);
 121         return ret;
 122 }
 123
 124 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
 125 {
 126         struct inode *inode = dentry->d_inode;
 127         struct kernfs_node *kn = dentry->d_fsdata;
 128         int error;
 129
 130         if (!kn)
 131                 return -EINVAL;
 132
 133         mutex_lock(&kernfs_mutex);
 134         error = inode_change_ok(inode, iattr);
 135         if (error)
 136                 goto out;
 137
 138         error = __kernfs_setattr(kn, iattr);
 139         if (error)
 140                 goto out;
 141
 142         /* this ignores size changes */
 143         setattr_copy(inode, iattr);
 144
 145 out:
 146         mutex_unlock(&kernfs_mutex);
 147         return error;
 148 }
 149
 150 static int kernfs_node_setsecdata(struct kernfs_node *kn, void **secdata,
 151                                   u32 *secdata_len)
 152 {
 153         struct kernfs_iattrs *attrs;
 154         void *old_secdata;
 155         size_t old_secdata_len;
 156
 157         attrs = kernfs_iattrs(kn);
 158         if (!attrs)
 159                 return -ENOMEM;
 160
 161         old_secdata = attrs->ia_secdata;
 162         old_secdata_len = attrs->ia_secdata_len;
 163
 164         attrs->ia_secdata = *secdata;
 165         attrs->ia_secdata_len = *secdata_len;
 166
 167         *secdata = old_secdata;
 168         *secdata_len = old_secdata_len;
 169         return 0;
 170 }
 171
 172 int kernfs_iop_setxattr(struct dentry *dentry, const char *name,
 173                         const void *value, size_t size, int flags)
 174 {
 175         struct kernfs_node *kn = dentry->d_fsdata;
 176         struct kernfs_iattrs *attrs;
 177         void *secdata;
 178         int error;
 179         u32 secdata_len = 0;
 180
 181         attrs = kernfs_iattrs(kn);
 182         if (!attrs)
 183                 return -ENOMEM;
 184
 185         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
 186                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 187                 error = security_inode_setsecurity(dentry->d_inode, suffix,
 188                                                 value, size, flags);
 189                 if (error)
 190                         return error;
 191                 error = security_inode_getsecctx(dentry->d_inode,
 192                                                 &secdata, &secdata_len);
 193                 if (error)
 194                         return error;
 195
 196                 mutex_lock(&kernfs_mutex);
 197                 error = kernfs_node_setsecdata(kn, &secdata, &secdata_len);
 198                 mutex_unlock(&kernfs_mutex);
 199
 200                 if (secdata)
 201                         security_release_secctx(secdata, secdata_len);
 202                 return error;
 203         } else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
 204                 return simple_xattr_set(&attrs->xattrs, name, value, size,
 205                                         flags);
 206         }
 207
 208         return -EINVAL;
 209 }
 210
 211 int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
 212 {
 213         struct kernfs_node *kn = dentry->d_fsdata;
 214         struct kernfs_iattrs *attrs;
 215
 216         attrs = kernfs_iattrs(kn);
 217         if (!attrs)
 218                 return -ENOMEM;
 219
 220         return simple_xattr_remove(&attrs->xattrs, name);
 221 }
 222
 223 ssize_t kernfs_iop_getxattr(struct dentry *dentry, const char *name, void *buf,
 224                             size_t size)
 225 {
 226         struct kernfs_node *kn = dentry->d_fsdata;
 227         struct kernfs_iattrs *attrs;
 228
 229         attrs = kernfs_iattrs(kn);
 230         if (!attrs)
 231                 return -ENOMEM;
 232
 233         return simple_xattr_get(&attrs->xattrs, name, buf, size);
 234 }
 235
 236 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
 237 {
 238         struct kernfs_node *kn = dentry->d_fsdata;
 239         struct kernfs_iattrs *attrs;
 240
 241         attrs = kernfs_iattrs(kn);
 242         if (!attrs)
 243                 return -ENOMEM;
 244
 245         return simple_xattr_list(&attrs->xattrs, buf, size);
 246 }
 247
 248 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
 249 {
 250         inode->i_mode = mode;
 251         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 252 }
 253
 254 static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
 255 {
 256         inode->i_uid = iattr->ia_uid;
 257         inode->i_gid = iattr->ia_gid;
 258         inode->i_atime = iattr->ia_atime;
 259         inode->i_mtime = iattr->ia_mtime;
 260         inode->i_ctime = iattr->ia_ctime;
 261 }
 262
 263 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
 264 {
 265         struct kernfs_iattrs *attrs = kn->iattr;
 266
 267         inode->i_mode = kn->mode;
 268         if (attrs) {
 269                 /*
 270                  * kernfs_node has non-default attributes get them from
 271                  * persistent copy in kernfs_node.
 272                  */
 273                 set_inode_attr(inode, &attrs->ia_iattr);
 274                 security_inode_notifysecctx(inode, attrs->ia_secdata,
 275                                             attrs->ia_secdata_len);
 276         }
 277
 278         if (kernfs_type(kn) == KERNFS_DIR)
 279                 set_nlink(inode, kn->dir.subdirs + 2);
 280 }
 281
 282 int kernfs_iop_getattr(struct vfsmount *mnt, struct dentry *dentry,
 283                    struct kstat *stat)
 284 {
 285         struct kernfs_node *kn = dentry->d_fsdata;
 286         struct inode *inode = dentry->d_inode;
 287
 288         mutex_lock(&kernfs_mutex);
 289         kernfs_refresh_inode(kn, inode);
 290         mutex_unlock(&kernfs_mutex);
 291
 292         generic_fillattr(inode, stat);
 293         return 0;
 294 }
 295
 296 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
 297 {
 298         kernfs_get(kn);
 299         inode->i_private = kn;
 300         inode->i_mapping->a_ops = &kernfs_aops;
 301         inode->i_mapping->backing_dev_info = &kernfs_bdi;
 302         inode->i_op = &kernfs_iops;
 303
 304         set_default_inode_attr(inode, kn->mode);
 305         kernfs_refresh_inode(kn, inode);
 306
 307         /* initialize inode according to type */
 308         switch (kernfs_type(kn)) {
 309         case KERNFS_DIR:
 310                 inode->i_op = &kernfs_dir_iops;
 311                 inode->i_fop = &kernfs_dir_fops;
 312                 break;
 313         case KERNFS_FILE:
 314                 inode->i_size = kn->attr.size;
 315                 inode->i_fop = &kernfs_file_fops;
 316                 break;
 317         case KERNFS_LINK:
 318                 inode->i_op = &kernfs_symlink_iops;
 319                 break;
 320         default:
 321                 BUG();
 322         }
 323
 324         unlock_new_inode(inode);
 325 }
 326
 327 /**
 328  *      kernfs_get_inode - get inode for kernfs_node
 329  *      @sb: super block
 330  *      @kn: kernfs_node to allocate inode for
 331  *
 332  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
 333  *      allocated and basics are initialized.  New inode is returned
 334  *      locked.
 335  *
 336  *      LOCKING:
 337  *      Kernel thread context (may sleep).
 338  *
 339  *      RETURNS:
 340  *      Pointer to allocated inode on success, NULL on failure.
 341  */
 342 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 343 {
 344         struct inode *inode;
 345
 346         inode = iget_locked(sb, kn->ino);
 347         if (inode && (inode->i_state & I_NEW))
 348                 kernfs_init_inode(kn, inode);
 349
 350         return inode;
 351 }
 352
 353 /*
 354  * The kernfs_node serves as both an inode and a directory entry for
 355  * kernfs.  To prevent the kernfs inode numbers from being freed
 356  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
 357  * super_operations.evict_inode() implementation is needed to drop that
 358  * reference upon inode destruction.
 359  */
 360 void kernfs_evict_inode(struct inode *inode)
 361 {
 362         struct kernfs_node *kn = inode->i_private;
 363
 364         truncate_inode_pages_final(&inode->i_data);
 365         clear_inode(inode);
 366         kernfs_put(kn);
 367 }
 368
 369 int kernfs_iop_permission(struct inode *inode, int mask)
 370 {
 371         struct kernfs_node *kn;
 372
 373         if (mask & MAY_NOT_BLOCK)
 374                 return -ECHILD;
 375
 376         kn = inode->i_private;
 377
 378         mutex_lock(&kernfs_mutex);
 379         kernfs_refresh_inode(kn, inode);
 380         mutex_unlock(&kernfs_mutex);
 381
 382         return generic_permission(inode, mask);
 383 }