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