1 /* 2 * inode.c - securityfs 3 * 4 * Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License version 8 * 2 as published by the Free Software Foundation. 9 * 10 * Based on fs/debugfs/inode.c which had the following copyright notice: 11 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com> 12 * Copyright (C) 2004 IBM Inc. 13 */ 14 15 /* #define DEBUG */ 16 #include <linux/sysfs.h> 17 #include <linux/kobject.h> 18 #include <linux/fs.h> 19 #include <linux/fs_context.h> 20 #include <linux/mount.h> 21 #include <linux/pagemap.h> 22 #include <linux/init.h> 23 #include <linux/namei.h> 24 #include <linux/security.h> 25 #include <linux/lsm_hooks.h> 26 #include <linux/magic.h> 27 28 static struct vfsmount *mount; 29 static int mount_count; 30 31 static void securityfs_free_inode(struct inode *inode) 32 { 33 if (S_ISLNK(inode->i_mode)) 34 kfree(inode->i_link); 35 free_inode_nonrcu(inode); 36 } 37 38 static const struct super_operations securityfs_super_operations = { 39 .statfs = simple_statfs, 40 .free_inode = securityfs_free_inode, 41 }; 42 43 static int securityfs_fill_super(struct super_block *sb, struct fs_context *fc) 44 { 45 static const struct tree_descr files[] = {{""}}; 46 int error; 47 48 error = simple_fill_super(sb, SECURITYFS_MAGIC, files); 49 if (error) 50 return error; 51 52 sb->s_op = &securityfs_super_operations; 53 54 return 0; 55 } 56 57 static int securityfs_get_tree(struct fs_context *fc) 58 { 59 return get_tree_single(fc, securityfs_fill_super); 60 } 61 62 static const struct fs_context_operations securityfs_context_ops = { 63 .get_tree = securityfs_get_tree, 64 }; 65 66 static int securityfs_init_fs_context(struct fs_context *fc) 67 { 68 fc->ops = &securityfs_context_ops; 69 return 0; 70 } 71 72 static struct file_system_type fs_type = { 73 .owner = THIS_MODULE, 74 .name = "securityfs", 75 .init_fs_context = securityfs_init_fs_context, 76 .kill_sb = kill_litter_super, 77 }; 78 79 /** 80 * securityfs_create_dentry - create a dentry in the securityfs filesystem 81 * 82 * @name: a pointer to a string containing the name of the file to create. 83 * @mode: the permission that the file should have 84 * @parent: a pointer to the parent dentry for this file. This should be a 85 * directory dentry if set. If this parameter is %NULL, then the 86 * file will be created in the root of the securityfs filesystem. 87 * @data: a pointer to something that the caller will want to get to later 88 * on. The inode.i_private pointer will point to this value on 89 * the open() call. 90 * @fops: a pointer to a struct file_operations that should be used for 91 * this file. 92 * @iops: a point to a struct of inode_operations that should be used for 93 * this file/dir 94 * 95 * This is the basic "create a file/dir/symlink" function for 96 * securityfs. It allows for a wide range of flexibility in creating 97 * a file, or a directory (if you want to create a directory, the 98 * securityfs_create_dir() function is recommended to be used 99 * instead). 100 * 101 * This function returns a pointer to a dentry if it succeeds. This 102 * pointer must be passed to the securityfs_remove() function when the 103 * file is to be removed (no automatic cleanup happens if your module 104 * is unloaded, you are responsible here). If an error occurs, the 105 * function will return the error value (via ERR_PTR). 106 * 107 * If securityfs is not enabled in the kernel, the value %-ENODEV is 108 * returned. 109 */ 110 static struct dentry *securityfs_create_dentry(const char *name, umode_t mode, 111 struct dentry *parent, void *data, 112 const struct file_operations *fops, 113 const struct inode_operations *iops) 114 { 115 struct dentry *dentry; 116 struct inode *dir, *inode; 117 int error; 118 119 if (!(mode & S_IFMT)) 120 mode = (mode & S_IALLUGO) | S_IFREG; 121 122 pr_debug("securityfs: creating file '%s'\n",name); 123 124 error = simple_pin_fs(&fs_type, &mount, &mount_count); 125 if (error) 126 return ERR_PTR(error); 127 128 if (!parent) 129 parent = mount->mnt_root; 130 131 dir = d_inode(parent); 132 133 inode_lock(dir); 134 dentry = lookup_one_len(name, parent, strlen(name)); 135 if (IS_ERR(dentry)) 136 goto out; 137 138 if (d_really_is_positive(dentry)) { 139 error = -EEXIST; 140 goto out1; 141 } 142 143 inode = new_inode(dir->i_sb); 144 if (!inode) { 145 error = -ENOMEM; 146 goto out1; 147 } 148 149 inode->i_ino = get_next_ino(); 150 inode->i_mode = mode; 151 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); 152 inode->i_private = data; 153 if (S_ISDIR(mode)) { 154 inode->i_op = &simple_dir_inode_operations; 155 inode->i_fop = &simple_dir_operations; 156 inc_nlink(inode); 157 inc_nlink(dir); 158 } else if (S_ISLNK(mode)) { 159 inode->i_op = iops ? iops : &simple_symlink_inode_operations; 160 inode->i_link = data; 161 } else { 162 inode->i_fop = fops; 163 } 164 d_instantiate(dentry, inode); 165 dget(dentry); 166 inode_unlock(dir); 167 return dentry; 168 169 out1: 170 dput(dentry); 171 dentry = ERR_PTR(error); 172 out: 173 inode_unlock(dir); 174 simple_release_fs(&mount, &mount_count); 175 return dentry; 176 } 177 178 /** 179 * securityfs_create_file - create a file in the securityfs filesystem 180 * 181 * @name: a pointer to a string containing the name of the file to create. 182 * @mode: the permission that the file should have 183 * @parent: a pointer to the parent dentry for this file. This should be a 184 * directory dentry if set. If this parameter is %NULL, then the 185 * file will be created in the root of the securityfs filesystem. 186 * @data: a pointer to something that the caller will want to get to later 187 * on. The inode.i_private pointer will point to this value on 188 * the open() call. 189 * @fops: a pointer to a struct file_operations that should be used for 190 * this file. 191 * 192 * This function creates a file in securityfs with the given @name. 193 * 194 * This function returns a pointer to a dentry if it succeeds. This 195 * pointer must be passed to the securityfs_remove() function when the file is 196 * to be removed (no automatic cleanup happens if your module is unloaded, 197 * you are responsible here). If an error occurs, the function will return 198 * the error value (via ERR_PTR). 199 * 200 * If securityfs is not enabled in the kernel, the value %-ENODEV is 201 * returned. 202 */ 203 struct dentry *securityfs_create_file(const char *name, umode_t mode, 204 struct dentry *parent, void *data, 205 const struct file_operations *fops) 206 { 207 return securityfs_create_dentry(name, mode, parent, data, fops, NULL); 208 } 209 EXPORT_SYMBOL_GPL(securityfs_create_file); 210 211 /** 212 * securityfs_create_dir - create a directory in the securityfs filesystem 213 * 214 * @name: a pointer to a string containing the name of the directory to 215 * create. 216 * @parent: a pointer to the parent dentry for this file. This should be a 217 * directory dentry if set. If this parameter is %NULL, then the 218 * directory will be created in the root of the securityfs filesystem. 219 * 220 * This function creates a directory in securityfs with the given @name. 221 * 222 * This function returns a pointer to a dentry if it succeeds. This 223 * pointer must be passed to the securityfs_remove() function when the file is 224 * to be removed (no automatic cleanup happens if your module is unloaded, 225 * you are responsible here). If an error occurs, the function will return 226 * the error value (via ERR_PTR). 227 * 228 * If securityfs is not enabled in the kernel, the value %-ENODEV is 229 * returned. 230 */ 231 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent) 232 { 233 return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL); 234 } 235 EXPORT_SYMBOL_GPL(securityfs_create_dir); 236 237 /** 238 * securityfs_create_symlink - create a symlink in the securityfs filesystem 239 * 240 * @name: a pointer to a string containing the name of the symlink to 241 * create. 242 * @parent: a pointer to the parent dentry for the symlink. This should be a 243 * directory dentry if set. If this parameter is %NULL, then the 244 * directory will be created in the root of the securityfs filesystem. 245 * @target: a pointer to a string containing the name of the symlink's target. 246 * If this parameter is %NULL, then the @iops parameter needs to be 247 * setup to handle .readlink and .get_link inode_operations. 248 * @iops: a pointer to the struct inode_operations to use for the symlink. If 249 * this parameter is %NULL, then the default simple_symlink_inode 250 * operations will be used. 251 * 252 * This function creates a symlink in securityfs with the given @name. 253 * 254 * This function returns a pointer to a dentry if it succeeds. This 255 * pointer must be passed to the securityfs_remove() function when the file is 256 * to be removed (no automatic cleanup happens if your module is unloaded, 257 * you are responsible here). If an error occurs, the function will return 258 * the error value (via ERR_PTR). 259 * 260 * If securityfs is not enabled in the kernel, the value %-ENODEV is 261 * returned. 262 */ 263 struct dentry *securityfs_create_symlink(const char *name, 264 struct dentry *parent, 265 const char *target, 266 const struct inode_operations *iops) 267 { 268 struct dentry *dent; 269 char *link = NULL; 270 271 if (target) { 272 link = kstrdup(target, GFP_KERNEL); 273 if (!link) 274 return ERR_PTR(-ENOMEM); 275 } 276 dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent, 277 link, NULL, iops); 278 if (IS_ERR(dent)) 279 kfree(link); 280 281 return dent; 282 } 283 EXPORT_SYMBOL_GPL(securityfs_create_symlink); 284 285 /** 286 * securityfs_remove - removes a file or directory from the securityfs filesystem 287 * 288 * @dentry: a pointer to a the dentry of the file or directory to be removed. 289 * 290 * This function removes a file or directory in securityfs that was previously 291 * created with a call to another securityfs function (like 292 * securityfs_create_file() or variants thereof.) 293 * 294 * This function is required to be called in order for the file to be 295 * removed. No automatic cleanup of files will happen when a module is 296 * removed; you are responsible here. 297 */ 298 void securityfs_remove(struct dentry *dentry) 299 { 300 struct inode *dir; 301 302 if (!dentry || IS_ERR(dentry)) 303 return; 304 305 dir = d_inode(dentry->d_parent); 306 inode_lock(dir); 307 if (simple_positive(dentry)) { 308 if (d_is_dir(dentry)) 309 simple_rmdir(dir, dentry); 310 else 311 simple_unlink(dir, dentry); 312 dput(dentry); 313 } 314 inode_unlock(dir); 315 simple_release_fs(&mount, &mount_count); 316 } 317 EXPORT_SYMBOL_GPL(securityfs_remove); 318 319 #ifdef CONFIG_SECURITY 320 static struct dentry *lsm_dentry; 321 static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count, 322 loff_t *ppos) 323 { 324 return simple_read_from_buffer(buf, count, ppos, lsm_names, 325 strlen(lsm_names)); 326 } 327 328 static const struct file_operations lsm_ops = { 329 .read = lsm_read, 330 .llseek = generic_file_llseek, 331 }; 332 #endif 333 334 static int __init securityfs_init(void) 335 { 336 int retval; 337 338 retval = sysfs_create_mount_point(kernel_kobj, "security"); 339 if (retval) 340 return retval; 341 342 retval = register_filesystem(&fs_type); 343 if (retval) { 344 sysfs_remove_mount_point(kernel_kobj, "security"); 345 return retval; 346 } 347 #ifdef CONFIG_SECURITY 348 lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL, 349 &lsm_ops); 350 #endif 351 return 0; 352 } 353 core_initcall(securityfs_init); 354