1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * fs/kernfs/inode.c - kernfs inode implementation 4 * 5 * Copyright (c) 2001-3 Patrick Mochel 6 * Copyright (c) 2007 SUSE Linux Products GmbH 7 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org> 8 */ 9 10 #include <linux/pagemap.h> 11 #include <linux/backing-dev.h> 12 #include <linux/capability.h> 13 #include <linux/errno.h> 14 #include <linux/slab.h> 15 #include <linux/xattr.h> 16 #include <linux/security.h> 17 18 #include "kernfs-internal.h" 19 20 static const struct address_space_operations kernfs_aops = { 21 .readpage = simple_readpage, 22 .write_begin = simple_write_begin, 23 .write_end = simple_write_end, 24 }; 25 26 static const struct inode_operations kernfs_iops = { 27 .permission = kernfs_iop_permission, 28 .setattr = kernfs_iop_setattr, 29 .getattr = kernfs_iop_getattr, 30 .listxattr = kernfs_iop_listxattr, 31 }; 32 33 static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc) 34 { 35 static DEFINE_MUTEX(iattr_mutex); 36 struct kernfs_iattrs *ret; 37 38 mutex_lock(&iattr_mutex); 39 40 if (kn->iattr || !alloc) 41 goto out_unlock; 42 43 kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL); 44 if (!kn->iattr) 45 goto out_unlock; 46 47 /* assign default attributes */ 48 kn->iattr->ia_uid = GLOBAL_ROOT_UID; 49 kn->iattr->ia_gid = GLOBAL_ROOT_GID; 50 51 ktime_get_real_ts64(&kn->iattr->ia_atime); 52 kn->iattr->ia_mtime = kn->iattr->ia_atime; 53 kn->iattr->ia_ctime = kn->iattr->ia_atime; 54 55 simple_xattrs_init(&kn->iattr->xattrs); 56 out_unlock: 57 ret = kn->iattr; 58 mutex_unlock(&iattr_mutex); 59 return ret; 60 } 61 62 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn) 63 { 64 return __kernfs_iattrs(kn, 1); 65 } 66 67 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn) 68 { 69 return __kernfs_iattrs(kn, 0); 70 } 71 72 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr) 73 { 74 struct kernfs_iattrs *attrs; 75 unsigned int ia_valid = iattr->ia_valid; 76 77 attrs = kernfs_iattrs(kn); 78 if (!attrs) 79 return -ENOMEM; 80 81 if (ia_valid & ATTR_UID) 82 attrs->ia_uid = iattr->ia_uid; 83 if (ia_valid & ATTR_GID) 84 attrs->ia_gid = iattr->ia_gid; 85 if (ia_valid & ATTR_ATIME) 86 attrs->ia_atime = iattr->ia_atime; 87 if (ia_valid & ATTR_MTIME) 88 attrs->ia_mtime = iattr->ia_mtime; 89 if (ia_valid & ATTR_CTIME) 90 attrs->ia_ctime = iattr->ia_ctime; 91 if (ia_valid & ATTR_MODE) 92 kn->mode = iattr->ia_mode; 93 return 0; 94 } 95 96 /** 97 * kernfs_setattr - set iattr on a node 98 * @kn: target node 99 * @iattr: iattr to set 100 * 101 * Returns 0 on success, -errno on failure. 102 */ 103 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr) 104 { 105 int ret; 106 107 mutex_lock(&kernfs_mutex); 108 ret = __kernfs_setattr(kn, iattr); 109 mutex_unlock(&kernfs_mutex); 110 return ret; 111 } 112 113 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr) 114 { 115 struct inode *inode = d_inode(dentry); 116 struct kernfs_node *kn = inode->i_private; 117 int error; 118 119 if (!kn) 120 return -EINVAL; 121 122 mutex_lock(&kernfs_mutex); 123 error = setattr_prepare(dentry, iattr); 124 if (error) 125 goto out; 126 127 error = __kernfs_setattr(kn, iattr); 128 if (error) 129 goto out; 130 131 /* this ignores size changes */ 132 setattr_copy(inode, iattr); 133 134 out: 135 mutex_unlock(&kernfs_mutex); 136 return error; 137 } 138 139 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size) 140 { 141 struct kernfs_node *kn = kernfs_dentry_node(dentry); 142 struct kernfs_iattrs *attrs; 143 144 attrs = kernfs_iattrs(kn); 145 if (!attrs) 146 return -ENOMEM; 147 148 return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size); 149 } 150 151 static inline void set_default_inode_attr(struct inode *inode, umode_t mode) 152 { 153 inode->i_mode = mode; 154 inode->i_atime = inode->i_mtime = 155 inode->i_ctime = current_time(inode); 156 } 157 158 static inline void set_inode_attr(struct inode *inode, 159 struct kernfs_iattrs *attrs) 160 { 161 inode->i_uid = attrs->ia_uid; 162 inode->i_gid = attrs->ia_gid; 163 inode->i_atime = timestamp_truncate(attrs->ia_atime, inode); 164 inode->i_mtime = timestamp_truncate(attrs->ia_mtime, inode); 165 inode->i_ctime = timestamp_truncate(attrs->ia_ctime, inode); 166 } 167 168 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode) 169 { 170 struct kernfs_iattrs *attrs = kn->iattr; 171 172 inode->i_mode = kn->mode; 173 if (attrs) 174 /* 175 * kernfs_node has non-default attributes get them from 176 * persistent copy in kernfs_node. 177 */ 178 set_inode_attr(inode, attrs); 179 180 if (kernfs_type(kn) == KERNFS_DIR) 181 set_nlink(inode, kn->dir.subdirs + 2); 182 } 183 184 int kernfs_iop_getattr(const struct path *path, struct kstat *stat, 185 u32 request_mask, unsigned int query_flags) 186 { 187 struct inode *inode = d_inode(path->dentry); 188 struct kernfs_node *kn = inode->i_private; 189 190 mutex_lock(&kernfs_mutex); 191 kernfs_refresh_inode(kn, inode); 192 mutex_unlock(&kernfs_mutex); 193 194 generic_fillattr(inode, stat); 195 return 0; 196 } 197 198 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode) 199 { 200 kernfs_get(kn); 201 inode->i_private = kn; 202 inode->i_mapping->a_ops = &kernfs_aops; 203 inode->i_op = &kernfs_iops; 204 inode->i_generation = kn->id.generation; 205 206 set_default_inode_attr(inode, kn->mode); 207 kernfs_refresh_inode(kn, inode); 208 209 /* initialize inode according to type */ 210 switch (kernfs_type(kn)) { 211 case KERNFS_DIR: 212 inode->i_op = &kernfs_dir_iops; 213 inode->i_fop = &kernfs_dir_fops; 214 if (kn->flags & KERNFS_EMPTY_DIR) 215 make_empty_dir_inode(inode); 216 break; 217 case KERNFS_FILE: 218 inode->i_size = kn->attr.size; 219 inode->i_fop = &kernfs_file_fops; 220 break; 221 case KERNFS_LINK: 222 inode->i_op = &kernfs_symlink_iops; 223 break; 224 default: 225 BUG(); 226 } 227 228 unlock_new_inode(inode); 229 } 230 231 /** 232 * kernfs_get_inode - get inode for kernfs_node 233 * @sb: super block 234 * @kn: kernfs_node to allocate inode for 235 * 236 * Get inode for @kn. If such inode doesn't exist, a new inode is 237 * allocated and basics are initialized. New inode is returned 238 * locked. 239 * 240 * LOCKING: 241 * Kernel thread context (may sleep). 242 * 243 * RETURNS: 244 * Pointer to allocated inode on success, NULL on failure. 245 */ 246 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn) 247 { 248 struct inode *inode; 249 250 inode = iget_locked(sb, kn->id.ino); 251 if (inode && (inode->i_state & I_NEW)) 252 kernfs_init_inode(kn, inode); 253 254 return inode; 255 } 256 257 /* 258 * The kernfs_node serves as both an inode and a directory entry for 259 * kernfs. To prevent the kernfs inode numbers from being freed 260 * prematurely we take a reference to kernfs_node from the kernfs inode. A 261 * super_operations.evict_inode() implementation is needed to drop that 262 * reference upon inode destruction. 263 */ 264 void kernfs_evict_inode(struct inode *inode) 265 { 266 struct kernfs_node *kn = inode->i_private; 267 268 truncate_inode_pages_final(&inode->i_data); 269 clear_inode(inode); 270 kernfs_put(kn); 271 } 272 273 int kernfs_iop_permission(struct inode *inode, int mask) 274 { 275 struct kernfs_node *kn; 276 277 if (mask & MAY_NOT_BLOCK) 278 return -ECHILD; 279 280 kn = inode->i_private; 281 282 mutex_lock(&kernfs_mutex); 283 kernfs_refresh_inode(kn, inode); 284 mutex_unlock(&kernfs_mutex); 285 286 return generic_permission(inode, mask); 287 } 288 289 int kernfs_xattr_get(struct kernfs_node *kn, const char *name, 290 void *value, size_t size) 291 { 292 struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn); 293 if (!attrs) 294 return -ENODATA; 295 296 return simple_xattr_get(&attrs->xattrs, name, value, size); 297 } 298 299 int kernfs_xattr_set(struct kernfs_node *kn, const char *name, 300 const void *value, size_t size, int flags) 301 { 302 struct kernfs_iattrs *attrs = kernfs_iattrs(kn); 303 if (!attrs) 304 return -ENOMEM; 305 306 return simple_xattr_set(&attrs->xattrs, name, value, size, flags); 307 } 308 309 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler, 310 struct dentry *unused, struct inode *inode, 311 const char *suffix, void *value, size_t size) 312 { 313 const char *name = xattr_full_name(handler, suffix); 314 struct kernfs_node *kn = inode->i_private; 315 316 return kernfs_xattr_get(kn, name, value, size); 317 } 318 319 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler, 320 struct dentry *unused, struct inode *inode, 321 const char *suffix, const void *value, 322 size_t size, int flags) 323 { 324 const char *name = xattr_full_name(handler, suffix); 325 struct kernfs_node *kn = inode->i_private; 326 327 return kernfs_xattr_set(kn, name, value, size, flags); 328 } 329 330 static const struct xattr_handler kernfs_trusted_xattr_handler = { 331 .prefix = XATTR_TRUSTED_PREFIX, 332 .get = kernfs_vfs_xattr_get, 333 .set = kernfs_vfs_xattr_set, 334 }; 335 336 static const struct xattr_handler kernfs_security_xattr_handler = { 337 .prefix = XATTR_SECURITY_PREFIX, 338 .get = kernfs_vfs_xattr_get, 339 .set = kernfs_vfs_xattr_set, 340 }; 341 342 const struct xattr_handler *kernfs_xattr_handlers[] = { 343 &kernfs_trusted_xattr_handler, 344 &kernfs_security_xattr_handler, 345 NULL 346 }; 347