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         .listxattr      = kernfs_iop_listxattr,
  32 };
  33
  34 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
  35 {
  36         static DEFINE_MUTEX(iattr_mutex);
  37         struct kernfs_iattrs *ret;
  38         struct iattr *iattrs;
  39
  40         mutex_lock(&iattr_mutex);
  41
  42         if (kn->iattr)
  43                 goto out_unlock;
  44
  45         kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
  46         if (!kn->iattr)
  47                 goto out_unlock;
  48         iattrs = &kn->iattr->ia_iattr;
  49
  50         /* assign default attributes */
  51         iattrs->ia_mode = kn->mode;
  52         iattrs->ia_uid = GLOBAL_ROOT_UID;
  53         iattrs->ia_gid = GLOBAL_ROOT_GID;
  54
  55         ktime_get_real_ts(&iattrs->ia_atime);
  56         iattrs->ia_mtime = iattrs->ia_atime;
  57         iattrs->ia_ctime = iattrs->ia_atime;
  58
  59         simple_xattrs_init(&kn->iattr->xattrs);
  60 out_unlock:
  61         ret = kn->iattr;
  62         mutex_unlock(&iattr_mutex);
  63         return ret;
  64 }
  65
  66 static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
  67 {
  68         struct kernfs_iattrs *attrs;
  69         struct iattr *iattrs;
  70         unsigned int ia_valid = iattr->ia_valid;
  71
  72         attrs = kernfs_iattrs(kn);
  73         if (!attrs)
  74                 return -ENOMEM;
  75
  76         iattrs = &attrs->ia_iattr;
  77
  78         if (ia_valid & ATTR_UID)
  79                 iattrs->ia_uid = iattr->ia_uid;
  80         if (ia_valid & ATTR_GID)
  81                 iattrs->ia_gid = iattr->ia_gid;
  82         if (ia_valid & ATTR_ATIME)
  83                 iattrs->ia_atime = iattr->ia_atime;
  84         if (ia_valid & ATTR_MTIME)
  85                 iattrs->ia_mtime = iattr->ia_mtime;
  86         if (ia_valid & ATTR_CTIME)
  87                 iattrs->ia_ctime = iattr->ia_ctime;
  88         if (ia_valid & ATTR_MODE) {
  89                 umode_t mode = iattr->ia_mode;
  90                 iattrs->ia_mode = kn->mode = mode;
  91         }
  92         return 0;
  93 }
  94
  95 /**
  96  * kernfs_setattr - set iattr on a node
  97  * @kn: target node
  98  * @iattr: iattr to set
  99  *
 100  * Returns 0 on success, -errno on failure.
 101  */
 102 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 103 {
 104         int ret;
 105
 106         mutex_lock(&kernfs_mutex);
 107         ret = __kernfs_setattr(kn, iattr);
 108         mutex_unlock(&kernfs_mutex);
 109         return ret;
 110 }
 111
 112 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
 113 {
 114         struct inode *inode = d_inode(dentry);
 115         struct kernfs_node *kn = dentry->d_fsdata;
 116         int error;
 117
 118         if (!kn)
 119                 return -EINVAL;
 120
 121         mutex_lock(&kernfs_mutex);
 122         error = setattr_prepare(dentry, iattr);
 123         if (error)
 124                 goto out;
 125
 126         error = __kernfs_setattr(kn, iattr);
 127         if (error)
 128                 goto out;
 129
 130         /* this ignores size changes */
 131         setattr_copy(inode, iattr);
 132
 133 out:
 134         mutex_unlock(&kernfs_mutex);
 135         return error;
 136 }
 137
 138 static int kernfs_node_setsecdata(struct kernfs_iattrs *attrs, void **secdata,
 139                                   u32 *secdata_len)
 140 {
 141         void *old_secdata;
 142         size_t old_secdata_len;
 143
 144         old_secdata = attrs->ia_secdata;
 145         old_secdata_len = attrs->ia_secdata_len;
 146
 147         attrs->ia_secdata = *secdata;
 148         attrs->ia_secdata_len = *secdata_len;
 149
 150         *secdata = old_secdata;
 151         *secdata_len = old_secdata_len;
 152         return 0;
 153 }
 154
 155 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
 156 {
 157         struct kernfs_node *kn = dentry->d_fsdata;
 158         struct kernfs_iattrs *attrs;
 159
 160         attrs = kernfs_iattrs(kn);
 161         if (!attrs)
 162                 return -ENOMEM;
 163
 164         return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
 165 }
 166
 167 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
 168 {
 169         inode->i_mode = mode;
 170         inode->i_atime = inode->i_mtime =
 171                 inode->i_ctime = current_time(inode);
 172 }
 173
 174 static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
 175 {
 176         struct super_block *sb = inode->i_sb;
 177         inode->i_uid = iattr->ia_uid;
 178         inode->i_gid = iattr->ia_gid;
 179         inode->i_atime = timespec_trunc(iattr->ia_atime, sb->s_time_gran);
 180         inode->i_mtime = timespec_trunc(iattr->ia_mtime, sb->s_time_gran);
 181         inode->i_ctime = timespec_trunc(iattr->ia_ctime, sb->s_time_gran);
 182 }
 183
 184 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
 185 {
 186         struct kernfs_iattrs *attrs = kn->iattr;
 187
 188         inode->i_mode = kn->mode;
 189         if (attrs) {
 190                 /*
 191                  * kernfs_node has non-default attributes get them from
 192                  * persistent copy in kernfs_node.
 193                  */
 194                 set_inode_attr(inode, &attrs->ia_iattr);
 195                 security_inode_notifysecctx(inode, attrs->ia_secdata,
 196                                             attrs->ia_secdata_len);
 197         }
 198
 199         if (kernfs_type(kn) == KERNFS_DIR)
 200                 set_nlink(inode, kn->dir.subdirs + 2);
 201 }
 202
 203 int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
 204                        u32 request_mask, unsigned int query_flags)
 205 {
 206         struct kernfs_node *kn = path->dentry->d_fsdata;
 207         struct inode *inode = d_inode(path->dentry);
 208
 209         mutex_lock(&kernfs_mutex);
 210         kernfs_refresh_inode(kn, inode);
 211         mutex_unlock(&kernfs_mutex);
 212
 213         generic_fillattr(inode, stat);
 214         return 0;
 215 }
 216
 217 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
 218 {
 219         kernfs_get(kn);
 220         inode->i_private = kn;
 221         inode->i_mapping->a_ops = &kernfs_aops;
 222         inode->i_op = &kernfs_iops;
 223
 224         set_default_inode_attr(inode, kn->mode);
 225         kernfs_refresh_inode(kn, inode);
 226
 227         /* initialize inode according to type */
 228         switch (kernfs_type(kn)) {
 229         case KERNFS_DIR:
 230                 inode->i_op = &kernfs_dir_iops;
 231                 inode->i_fop = &kernfs_dir_fops;
 232                 if (kn->flags & KERNFS_EMPTY_DIR)
 233                         make_empty_dir_inode(inode);
 234                 break;
 235         case KERNFS_FILE:
 236                 inode->i_size = kn->attr.size;
 237                 inode->i_fop = &kernfs_file_fops;
 238                 break;
 239         case KERNFS_LINK:
 240                 inode->i_op = &kernfs_symlink_iops;
 241                 break;
 242         default:
 243                 BUG();
 244         }
 245
 246         unlock_new_inode(inode);
 247 }
 248
 249 /**
 250  *      kernfs_get_inode - get inode for kernfs_node
 251  *      @sb: super block
 252  *      @kn: kernfs_node to allocate inode for
 253  *
 254  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
 255  *      allocated and basics are initialized.  New inode is returned
 256  *      locked.
 257  *
 258  *      LOCKING:
 259  *      Kernel thread context (may sleep).
 260  *
 261  *      RETURNS:
 262  *      Pointer to allocated inode on success, NULL on failure.
 263  */
 264 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 265 {
 266         struct inode *inode;
 267
 268         inode = iget_locked(sb, kn->ino);
 269         if (inode && (inode->i_state & I_NEW))
 270                 kernfs_init_inode(kn, inode);
 271
 272         return inode;
 273 }
 274
 275 /*
 276  * The kernfs_node serves as both an inode and a directory entry for
 277  * kernfs.  To prevent the kernfs inode numbers from being freed
 278  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
 279  * super_operations.evict_inode() implementation is needed to drop that
 280  * reference upon inode destruction.
 281  */
 282 void kernfs_evict_inode(struct inode *inode)
 283 {
 284         struct kernfs_node *kn = inode->i_private;
 285
 286         truncate_inode_pages_final(&inode->i_data);
 287         clear_inode(inode);
 288         kernfs_put(kn);
 289 }
 290
 291 int kernfs_iop_permission(struct inode *inode, int mask)
 292 {
 293         struct kernfs_node *kn;
 294
 295         if (mask & MAY_NOT_BLOCK)
 296                 return -ECHILD;
 297
 298         kn = inode->i_private;
 299
 300         mutex_lock(&kernfs_mutex);
 301         kernfs_refresh_inode(kn, inode);
 302         mutex_unlock(&kernfs_mutex);
 303
 304         return generic_permission(inode, mask);
 305 }
 306
 307 static int kernfs_xattr_get(const struct xattr_handler *handler,
 308                             struct dentry *unused, struct inode *inode,
 309                             const char *suffix, void *value, size_t size)
 310 {
 311         const char *name = xattr_full_name(handler, suffix);
 312         struct kernfs_node *kn = inode->i_private;
 313         struct kernfs_iattrs *attrs;
 314
 315         attrs = kernfs_iattrs(kn);
 316         if (!attrs)
 317                 return -ENOMEM;
 318
 319         return simple_xattr_get(&attrs->xattrs, name, value, size);
 320 }
 321
 322 static int kernfs_xattr_set(const struct xattr_handler *handler,
 323                             struct dentry *unused, struct inode *inode,
 324                             const char *suffix, const void *value,
 325                             size_t size, int flags)
 326 {
 327         const char *name = xattr_full_name(handler, suffix);
 328         struct kernfs_node *kn = inode->i_private;
 329         struct kernfs_iattrs *attrs;
 330
 331         attrs = kernfs_iattrs(kn);
 332         if (!attrs)
 333                 return -ENOMEM;
 334
 335         return simple_xattr_set(&attrs->xattrs, name, value, size, flags);
 336 }
 337
 338 static const struct xattr_handler kernfs_trusted_xattr_handler = {
 339         .prefix = XATTR_TRUSTED_PREFIX,
 340         .get = kernfs_xattr_get,
 341         .set = kernfs_xattr_set,
 342 };
 343
 344 static int kernfs_security_xattr_set(const struct xattr_handler *handler,
 345                                      struct dentry *unused, struct inode *inode,
 346                                      const char *suffix, const void *value,
 347                                      size_t size, int flags)
 348 {
 349         struct kernfs_node *kn = inode->i_private;
 350         struct kernfs_iattrs *attrs;
 351         void *secdata;
 352         u32 secdata_len = 0;
 353         int error;
 354
 355         attrs = kernfs_iattrs(kn);
 356         if (!attrs)
 357                 return -ENOMEM;
 358
 359         error = security_inode_setsecurity(inode, suffix, value, size, flags);
 360         if (error)
 361                 return error;
 362         error = security_inode_getsecctx(inode, &secdata, &secdata_len);
 363         if (error)
 364                 return error;
 365
 366         mutex_lock(&kernfs_mutex);
 367         error = kernfs_node_setsecdata(attrs, &secdata, &secdata_len);
 368         mutex_unlock(&kernfs_mutex);
 369
 370         if (secdata)
 371                 security_release_secctx(secdata, secdata_len);
 372         return error;
 373 }
 374
 375 static const struct xattr_handler kernfs_security_xattr_handler = {
 376         .prefix = XATTR_SECURITY_PREFIX,
 377         .get = kernfs_xattr_get,
 378         .set = kernfs_security_xattr_set,
 379 };
 380
 381 const struct xattr_handler *kernfs_xattr_handlers[] = {
 382         &kernfs_trusted_xattr_handler,
 383         &kernfs_security_xattr_handler,
 384         NULL
 385 };