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