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_ts64(&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 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 = inode->i_private;
 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 = kernfs_dentry_node(dentry);
 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 = timespec64_trunc(iattr->ia_atime, sb->s_time_gran);
 180         inode->i_mtime = timespec64_trunc(iattr->ia_mtime, sb->s_time_gran);
 181         inode->i_ctime = timespec64_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 inode *inode = d_inode(path->dentry);
 207         struct kernfs_node *kn = inode->i_private;
 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         inode->i_generation = kn->id.generation;
 224
 225         set_default_inode_attr(inode, kn->mode);
 226         kernfs_refresh_inode(kn, inode);
 227
 228         /* initialize inode according to type */
 229         switch (kernfs_type(kn)) {
 230         case KERNFS_DIR:
 231                 inode->i_op = &kernfs_dir_iops;
 232                 inode->i_fop = &kernfs_dir_fops;
 233                 if (kn->flags & KERNFS_EMPTY_DIR)
 234                         make_empty_dir_inode(inode);
 235                 break;
 236         case KERNFS_FILE:
 237                 inode->i_size = kn->attr.size;
 238                 inode->i_fop = &kernfs_file_fops;
 239                 break;
 240         case KERNFS_LINK:
 241                 inode->i_op = &kernfs_symlink_iops;
 242                 break;
 243         default:
 244                 BUG();
 245         }
 246
 247         unlock_new_inode(inode);
 248 }
 249
 250 /**
 251  *      kernfs_get_inode - get inode for kernfs_node
 252  *      @sb: super block
 253  *      @kn: kernfs_node to allocate inode for
 254  *
 255  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
 256  *      allocated and basics are initialized.  New inode is returned
 257  *      locked.
 258  *
 259  *      LOCKING:
 260  *      Kernel thread context (may sleep).
 261  *
 262  *      RETURNS:
 263  *      Pointer to allocated inode on success, NULL on failure.
 264  */
 265 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 266 {
 267         struct inode *inode;
 268
 269         inode = iget_locked(sb, kn->id.ino);
 270         if (inode && (inode->i_state & I_NEW))
 271                 kernfs_init_inode(kn, inode);
 272
 273         return inode;
 274 }
 275
 276 /*
 277  * The kernfs_node serves as both an inode and a directory entry for
 278  * kernfs.  To prevent the kernfs inode numbers from being freed
 279  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
 280  * super_operations.evict_inode() implementation is needed to drop that
 281  * reference upon inode destruction.
 282  */
 283 void kernfs_evict_inode(struct inode *inode)
 284 {
 285         struct kernfs_node *kn = inode->i_private;
 286
 287         truncate_inode_pages_final(&inode->i_data);
 288         clear_inode(inode);
 289         kernfs_put(kn);
 290 }
 291
 292 int kernfs_iop_permission(struct inode *inode, int mask)
 293 {
 294         struct kernfs_node *kn;
 295
 296         if (mask & MAY_NOT_BLOCK)
 297                 return -ECHILD;
 298
 299         kn = inode->i_private;
 300
 301         mutex_lock(&kernfs_mutex);
 302         kernfs_refresh_inode(kn, inode);
 303         mutex_unlock(&kernfs_mutex);
 304
 305         return generic_permission(inode, mask);
 306 }
 307
 308 static int kernfs_xattr_get(const struct xattr_handler *handler,
 309                             struct dentry *unused, struct inode *inode,
 310                             const char *suffix, void *value, size_t size)
 311 {
 312         const char *name = xattr_full_name(handler, suffix);
 313         struct kernfs_node *kn = inode->i_private;
 314         struct kernfs_iattrs *attrs;
 315
 316         attrs = kernfs_iattrs(kn);
 317         if (!attrs)
 318                 return -ENOMEM;
 319
 320         return simple_xattr_get(&attrs->xattrs, name, value, size);
 321 }
 322
 323 static int kernfs_xattr_set(const struct xattr_handler *handler,
 324                             struct dentry *unused, struct inode *inode,
 325                             const char *suffix, const void *value,
 326                             size_t size, int flags)
 327 {
 328         const char *name = xattr_full_name(handler, suffix);
 329         struct kernfs_node *kn = inode->i_private;
 330         struct kernfs_iattrs *attrs;
 331
 332         attrs = kernfs_iattrs(kn);
 333         if (!attrs)
 334                 return -ENOMEM;
 335
 336         return simple_xattr_set(&attrs->xattrs, name, value, size, flags);
 337 }
 338
 339 static const struct xattr_handler kernfs_trusted_xattr_handler = {
 340         .prefix = XATTR_TRUSTED_PREFIX,
 341         .get = kernfs_xattr_get,
 342         .set = kernfs_xattr_set,
 343 };
 344
 345 static int kernfs_security_xattr_set(const struct xattr_handler *handler,
 346                                      struct dentry *unused, struct inode *inode,
 347                                      const char *suffix, const void *value,
 348                                      size_t size, int flags)
 349 {
 350         struct kernfs_node *kn = inode->i_private;
 351         struct kernfs_iattrs *attrs;
 352         void *secdata;
 353         u32 secdata_len = 0;
 354         int error;
 355
 356         attrs = kernfs_iattrs(kn);
 357         if (!attrs)
 358                 return -ENOMEM;
 359
 360         error = security_inode_setsecurity(inode, suffix, value, size, flags);
 361         if (error)
 362                 return error;
 363         error = security_inode_getsecctx(inode, &secdata, &secdata_len);
 364         if (error)
 365                 return error;
 366
 367         mutex_lock(&kernfs_mutex);
 368         error = kernfs_node_setsecdata(attrs, &secdata, &secdata_len);
 369         mutex_unlock(&kernfs_mutex);
 370
 371         if (secdata)
 372                 security_release_secctx(secdata, secdata_len);
 373         return error;
 374 }
 375
 376 static const struct xattr_handler kernfs_security_xattr_handler = {
 377         .prefix = XATTR_SECURITY_PREFIX,
 378         .get = kernfs_xattr_get,
 379         .set = kernfs_security_xattr_set,
 380 };
 381
 382 const struct xattr_handler *kernfs_xattr_handlers[] = {
 383         &kernfs_trusted_xattr_handler,
 384         &kernfs_security_xattr_handler,
 385         NULL
 386 };