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         iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
  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 = dentry->d_inode;
 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 = inode_change_ok(inode, 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_node *kn, void **secdata,
 139                                   u32 *secdata_len)
 140 {
 141         struct kernfs_iattrs *attrs;
 142         void *old_secdata;
 143         size_t old_secdata_len;
 144
 145         attrs = kernfs_iattrs(kn);
 146         if (!attrs)
 147                 return -ENOMEM;
 148
 149         old_secdata = attrs->ia_secdata;
 150         old_secdata_len = attrs->ia_secdata_len;
 151
 152         attrs->ia_secdata = *secdata;
 153         attrs->ia_secdata_len = *secdata_len;
 154
 155         *secdata = old_secdata;
 156         *secdata_len = old_secdata_len;
 157         return 0;
 158 }
 159
 160 int kernfs_iop_setxattr(struct dentry *dentry, const char *name,
 161                         const void *value, size_t size, int flags)
 162 {
 163         struct kernfs_node *kn = dentry->d_fsdata;
 164         struct kernfs_iattrs *attrs;
 165         void *secdata;
 166         int error;
 167         u32 secdata_len = 0;
 168
 169         attrs = kernfs_iattrs(kn);
 170         if (!attrs)
 171                 return -ENOMEM;
 172
 173         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
 174                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 175                 error = security_inode_setsecurity(dentry->d_inode, suffix,
 176                                                 value, size, flags);
 177                 if (error)
 178                         return error;
 179                 error = security_inode_getsecctx(dentry->d_inode,
 180                                                 &secdata, &secdata_len);
 181                 if (error)
 182                         return error;
 183
 184                 mutex_lock(&kernfs_mutex);
 185                 error = kernfs_node_setsecdata(kn, &secdata, &secdata_len);
 186                 mutex_unlock(&kernfs_mutex);
 187
 188                 if (secdata)
 189                         security_release_secctx(secdata, secdata_len);
 190                 return error;
 191         } else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
 192                 return simple_xattr_set(&attrs->xattrs, name, value, size,
 193                                         flags);
 194         }
 195
 196         return -EINVAL;
 197 }
 198
 199 int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
 200 {
 201         struct kernfs_node *kn = dentry->d_fsdata;
 202         struct kernfs_iattrs *attrs;
 203
 204         attrs = kernfs_iattrs(kn);
 205         if (!attrs)
 206                 return -ENOMEM;
 207
 208         return simple_xattr_remove(&attrs->xattrs, name);
 209 }
 210
 211 ssize_t kernfs_iop_getxattr(struct dentry *dentry, const char *name, void *buf,
 212                             size_t size)
 213 {
 214         struct kernfs_node *kn = dentry->d_fsdata;
 215         struct kernfs_iattrs *attrs;
 216
 217         attrs = kernfs_iattrs(kn);
 218         if (!attrs)
 219                 return -ENOMEM;
 220
 221         return simple_xattr_get(&attrs->xattrs, name, buf, size);
 222 }
 223
 224 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, 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_list(&attrs->xattrs, buf, size);
 234 }
 235
 236 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
 237 {
 238         inode->i_mode = mode;
 239         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 240 }
 241
 242 static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
 243 {
 244         inode->i_uid = iattr->ia_uid;
 245         inode->i_gid = iattr->ia_gid;
 246         inode->i_atime = iattr->ia_atime;
 247         inode->i_mtime = iattr->ia_mtime;
 248         inode->i_ctime = iattr->ia_ctime;
 249 }
 250
 251 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
 252 {
 253         struct kernfs_iattrs *attrs = kn->iattr;
 254
 255         inode->i_mode = kn->mode;
 256         if (attrs) {
 257                 /*
 258                  * kernfs_node has non-default attributes get them from
 259                  * persistent copy in kernfs_node.
 260                  */
 261                 set_inode_attr(inode, &attrs->ia_iattr);
 262                 security_inode_notifysecctx(inode, attrs->ia_secdata,
 263                                             attrs->ia_secdata_len);
 264         }
 265
 266         if (kernfs_type(kn) == KERNFS_DIR)
 267                 set_nlink(inode, kn->dir.subdirs + 2);
 268 }
 269
 270 int kernfs_iop_getattr(struct vfsmount *mnt, struct dentry *dentry,
 271                    struct kstat *stat)
 272 {
 273         struct kernfs_node *kn = dentry->d_fsdata;
 274         struct inode *inode = dentry->d_inode;
 275
 276         mutex_lock(&kernfs_mutex);
 277         kernfs_refresh_inode(kn, inode);
 278         mutex_unlock(&kernfs_mutex);
 279
 280         generic_fillattr(inode, stat);
 281         return 0;
 282 }
 283
 284 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
 285 {
 286         kernfs_get(kn);
 287         inode->i_private = kn;
 288         inode->i_mapping->a_ops = &kernfs_aops;
 289         inode->i_op = &kernfs_iops;
 290
 291         set_default_inode_attr(inode, kn->mode);
 292         kernfs_refresh_inode(kn, inode);
 293
 294         /* initialize inode according to type */
 295         switch (kernfs_type(kn)) {
 296         case KERNFS_DIR:
 297                 inode->i_op = &kernfs_dir_iops;
 298                 inode->i_fop = &kernfs_dir_fops;
 299                 break;
 300         case KERNFS_FILE:
 301                 inode->i_size = kn->attr.size;
 302                 inode->i_fop = &kernfs_file_fops;
 303                 break;
 304         case KERNFS_LINK:
 305                 inode->i_op = &kernfs_symlink_iops;
 306                 break;
 307         default:
 308                 BUG();
 309         }
 310
 311         unlock_new_inode(inode);
 312 }
 313
 314 /**
 315  *      kernfs_get_inode - get inode for kernfs_node
 316  *      @sb: super block
 317  *      @kn: kernfs_node to allocate inode for
 318  *
 319  *      Get inode for @kn.  If such inode doesn't exist, a new inode is
 320  *      allocated and basics are initialized.  New inode is returned
 321  *      locked.
 322  *
 323  *      LOCKING:
 324  *      Kernel thread context (may sleep).
 325  *
 326  *      RETURNS:
 327  *      Pointer to allocated inode on success, NULL on failure.
 328  */
 329 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 330 {
 331         struct inode *inode;
 332
 333         inode = iget_locked(sb, kn->ino);
 334         if (inode && (inode->i_state & I_NEW))
 335                 kernfs_init_inode(kn, inode);
 336
 337         return inode;
 338 }
 339
 340 /*
 341  * The kernfs_node serves as both an inode and a directory entry for
 342  * kernfs.  To prevent the kernfs inode numbers from being freed
 343  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
 344  * super_operations.evict_inode() implementation is needed to drop that
 345  * reference upon inode destruction.
 346  */
 347 void kernfs_evict_inode(struct inode *inode)
 348 {
 349         struct kernfs_node *kn = inode->i_private;
 350
 351         truncate_inode_pages_final(&inode->i_data);
 352         clear_inode(inode);
 353         kernfs_put(kn);
 354 }
 355
 356 int kernfs_iop_permission(struct inode *inode, int mask)
 357 {
 358         struct kernfs_node *kn;
 359
 360         if (mask & MAY_NOT_BLOCK)
 361                 return -ECHILD;
 362
 363         kn = inode->i_private;
 364
 365         mutex_lock(&kernfs_mutex);
 366         kernfs_refresh_inode(kn, inode);
 367         mutex_unlock(&kernfs_mutex);
 368
 369         return generic_permission(inode, mask);
 370 }