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         struct iattr *iattrs;
  52
  53         if (kn->iattr)
  54                 return kn->iattr;
  55
  56         kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
  57         if (!kn->iattr)
  58                 return NULL;
  59         iattrs = &kn->iattr->ia_iattr;
  60
  61         /* assign default attributes */
  62         iattrs->ia_mode = kn->mode;
  63         iattrs->ia_uid = GLOBAL_ROOT_UID;
  64         iattrs->ia_gid = GLOBAL_ROOT_GID;
  65         iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
  66
  67         simple_xattrs_init(&kn->iattr->xattrs);
  68
  69         return kn->iattr;
  70 }
  71
  72 static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
  73 {
  74         struct kernfs_iattrs *attrs;
  75         struct iattr *iattrs;
  76         unsigned int ia_valid = iattr->ia_valid;
  77
  78         attrs = kernfs_iattrs(kn);
  79         if (!attrs)
  80                 return -ENOMEM;
  81
  82         iattrs = &attrs->ia_iattr;
  83
  84         if (ia_valid & ATTR_UID)
  85                 iattrs->ia_uid = iattr->ia_uid;
  86         if (ia_valid & ATTR_GID)
  87                 iattrs->ia_gid = iattr->ia_gid;
  88         if (ia_valid & ATTR_ATIME)
  89                 iattrs->ia_atime = iattr->ia_atime;
  90         if (ia_valid & ATTR_MTIME)
  91                 iattrs->ia_mtime = iattr->ia_mtime;
  92         if (ia_valid & ATTR_CTIME)
  93                 iattrs->ia_ctime = iattr->ia_ctime;
  94         if (ia_valid & ATTR_MODE) {
  95                 umode_t mode = iattr->ia_mode;
  96                 iattrs->ia_mode = kn->mode = mode;
  97         }
  98         return 0;
  99 }
 100
 101 /**
 102  * kernfs_setattr - set iattr on a node
 103  * @kn: target node
 104  * @iattr: iattr to set
 105  *
 106  * Returns 0 on success, -errno on failure.
 107  */
 108 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 109 {
 110         int ret;
 111
 112         mutex_lock(&kernfs_mutex);
 113         ret = __kernfs_setattr(kn, iattr);
 114         mutex_unlock(&kernfs_mutex);
 115         return ret;
 116 }
 117
 118 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
 119 {
 120         struct inode *inode = dentry->d_inode;
 121         struct kernfs_node *kn = dentry->d_fsdata;
 122         int error;
 123
 124         if (!kn)
 125                 return -EINVAL;
 126
 127         mutex_lock(&kernfs_mutex);
 128         error = inode_change_ok(inode, iattr);
 129         if (error)
 130                 goto out;
 131
 132         error = __kernfs_setattr(kn, iattr);
 133         if (error)
 134                 goto out;
 135
 136         /* this ignores size changes */
 137         setattr_copy(inode, iattr);
 138
 139 out:
 140         mutex_unlock(&kernfs_mutex);
 141         return error;
 142 }
 143
 144 static int kernfs_node_setsecdata(struct kernfs_node *kn, void **secdata,
 145                                   u32 *secdata_len)
 146 {
 147         struct kernfs_iattrs *attrs;
 148         void *old_secdata;
 149         size_t old_secdata_len;
 150
 151         attrs = kernfs_iattrs(kn);
 152         if (!attrs)
 153                 return -ENOMEM;
 154
 155         old_secdata = attrs->ia_secdata;
 156         old_secdata_len = attrs->ia_secdata_len;
 157
 158         attrs->ia_secdata = *secdata;
 159         attrs->ia_secdata_len = *secdata_len;
 160
 161         *secdata = old_secdata;
 162         *secdata_len = old_secdata_len;
 163         return 0;
 164 }
 165
 166 int kernfs_iop_setxattr(struct dentry *dentry, const char *name,
 167                         const void *value, size_t size, int flags)
 168 {
 169         struct kernfs_node *kn = dentry->d_fsdata;
 170         struct kernfs_iattrs *attrs;
 171         void *secdata;
 172         int error;
 173         u32 secdata_len = 0;
 174
 175         attrs = kernfs_iattrs(kn);
 176         if (!attrs)
 177                 return -ENOMEM;
 178
 179         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
 180                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 181                 error = security_inode_setsecurity(dentry->d_inode, suffix,
 182                                                 value, size, flags);
 183                 if (error)
 184                         return error;
 185                 error = security_inode_getsecctx(dentry->d_inode,
 186                                                 &secdata, &secdata_len);
 187                 if (error)
 188                         return error;
 189
 190                 mutex_lock(&kernfs_mutex);
 191                 error = kernfs_node_setsecdata(kn, &secdata, &secdata_len);
 192                 mutex_unlock(&kernfs_mutex);
 193
 194                 if (secdata)
 195                         security_release_secctx(secdata, secdata_len);
 196                 return error;
 197         } else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
 198                 return simple_xattr_set(&attrs->xattrs, name, value, size,
 199                                         flags);
 200         }
 201
 202         return -EINVAL;
 203 }
 204
 205 int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
 206 {
 207         struct kernfs_node *kn = dentry->d_fsdata;
 208         struct kernfs_iattrs *attrs;
 209
 210         attrs = kernfs_iattrs(kn);
 211         if (!attrs)
 212                 return -ENOMEM;
 213
 214         return simple_xattr_remove(&attrs->xattrs, name);
 215 }
 216
 217 ssize_t kernfs_iop_getxattr(struct dentry *dentry, const char *name, void *buf,
 218                             size_t size)
 219 {
 220         struct kernfs_node *kn = dentry->d_fsdata;
 221         struct kernfs_iattrs *attrs;
 222
 223         attrs = kernfs_iattrs(kn);
 224         if (!attrs)
 225                 return -ENOMEM;
 226
 227         return simple_xattr_get(&attrs->xattrs, name, buf, size);
 228 }
 229
 230 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
 231 {
 232         struct kernfs_node *kn = dentry->d_fsdata;
 233         struct kernfs_iattrs *attrs;
 234
 235         attrs = kernfs_iattrs(kn);
 236         if (!attrs)
 237                 return -ENOMEM;
 238
 239         return simple_xattr_list(&attrs->xattrs, buf, size);
 240 }
 241
 242 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
 243 {
 244         inode->i_mode = mode;
 245         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 246 }
 247
 248 static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
 249 {
 250         inode->i_uid = iattr->ia_uid;
 251         inode->i_gid = iattr->ia_gid;
 252         inode->i_atime = iattr->ia_atime;
 253         inode->i_mtime = iattr->ia_mtime;
 254         inode->i_ctime = iattr->ia_ctime;
 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 = dentry->d_inode;
 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_mapping->backing_dev_info = &kernfs_bdi;
 296         inode->i_op = &kernfs_iops;
 297
 298         set_default_inode_attr(inode, kn->mode);
 299         kernfs_refresh_inode(kn, inode);
 300
 301         /* initialize inode according to type */
 302         switch (kernfs_type(kn)) {
 303         case KERNFS_DIR:
 304                 inode->i_op = &kernfs_dir_iops;
 305                 inode->i_fop = &kernfs_dir_fops;
 306                 break;
 307         case KERNFS_FILE:
 308                 inode->i_size = kn->attr.size;
 309                 inode->i_fop = &kernfs_file_fops;
 310                 break;
 311         case KERNFS_LINK:
 312                 inode->i_op = &kernfs_symlink_iops;
 313                 break;
 314         default:
 315                 BUG();
 316         }
 317
 318         unlock_new_inode(inode);
 319 }
 320
 321 /**
 322  *      kernfs_get_inode - get inode for kernfs_node
 323  *      @sb: super block
 324  *      @kn: kernfs_node to allocate inode for
 325  *
 326  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
 327  *      allocated and basics are initialized.  New inode is returned
 328  *      locked.
 329  *
 330  *      LOCKING:
 331  *      Kernel thread context (may sleep).
 332  *
 333  *      RETURNS:
 334  *      Pointer to allocated inode on success, NULL on failure.
 335  */
 336 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 337 {
 338         struct inode *inode;
 339
 340         inode = iget_locked(sb, kn->ino);
 341         if (inode && (inode->i_state & I_NEW))
 342                 kernfs_init_inode(kn, inode);
 343
 344         return inode;
 345 }
 346
 347 /*
 348  * The kernfs_node serves as both an inode and a directory entry for
 349  * kernfs.  To prevent the kernfs inode numbers from being freed
 350  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
 351  * super_operations.evict_inode() implementation is needed to drop that
 352  * reference upon inode destruction.
 353  */
 354 void kernfs_evict_inode(struct inode *inode)
 355 {
 356         struct kernfs_node *kn = inode->i_private;
 357
 358         truncate_inode_pages(&inode->i_data, 0);
 359         clear_inode(inode);
 360         kernfs_put(kn);
 361 }
 362
 363 int kernfs_iop_permission(struct inode *inode, int mask)
 364 {
 365         struct kernfs_node *kn;
 366
 367         if (mask & MAY_NOT_BLOCK)
 368                 return -ECHILD;
 369
 370         kn = inode->i_private;
 371
 372         mutex_lock(&kernfs_mutex);
 373         kernfs_refresh_inode(kn, inode);
 374         mutex_unlock(&kernfs_mutex);
 375
 376         return generic_permission(inode, mask);
 377 }