| 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 = 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 = 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 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 | }; |