1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 4 */ 5 6 #include <stdio.h> 7 #include <stdlib.h> 8 #include <dirent.h> 9 #include <errno.h> 10 #include <fcntl.h> 11 #include <signal.h> 12 #include <string.h> 13 #include <unistd.h> 14 #include <sys/stat.h> 15 #include <init.h> 16 #include <os.h> 17 18 #define UML_DIR "~/.uml/" 19 20 #define UMID_LEN 64 21 22 /* Changed by set_umid, which is run early in boot */ 23 static char umid[UMID_LEN] = { 0 }; 24 25 /* Changed by set_uml_dir and make_uml_dir, which are run early in boot */ 26 static char *uml_dir = UML_DIR; 27 28 static int __init make_uml_dir(void) 29 { 30 char dir[512] = { '\0' }; 31 int len, err; 32 33 if (*uml_dir == '~') { 34 char *home = getenv("HOME"); 35 36 err = -ENOENT; 37 if (home == NULL) { 38 printk(UM_KERN_ERR 39 "%s: no value in environment for $HOME\n", 40 __func__); 41 goto err; 42 } 43 strlcpy(dir, home, sizeof(dir)); 44 uml_dir++; 45 } 46 strlcat(dir, uml_dir, sizeof(dir)); 47 len = strlen(dir); 48 if (len > 0 && dir[len - 1] != '/') 49 strlcat(dir, "/", sizeof(dir)); 50 51 err = -ENOMEM; 52 uml_dir = malloc(strlen(dir) + 1); 53 if (uml_dir == NULL) { 54 printk(UM_KERN_ERR "%s : malloc failed, errno = %d\n", 55 __func__, errno); 56 goto err; 57 } 58 strcpy(uml_dir, dir); 59 60 if ((mkdir(uml_dir, 0777) < 0) && (errno != EEXIST)) { 61 printk(UM_KERN_ERR "Failed to mkdir '%s': %s\n", 62 uml_dir, strerror(errno)); 63 err = -errno; 64 goto err_free; 65 } 66 return 0; 67 68 err_free: 69 free(uml_dir); 70 err: 71 uml_dir = NULL; 72 return err; 73 } 74 75 /* 76 * Unlinks the files contained in @dir and then removes @dir. 77 * Doesn't handle directory trees, so it's not like rm -rf, but almost such. We 78 * ignore ENOENT errors for anything (they happen, strangely enough - possibly 79 * due to races between multiple dying UML threads). 80 */ 81 static int remove_files_and_dir(char *dir) 82 { 83 DIR *directory; 84 struct dirent *ent; 85 int len; 86 char file[256]; 87 int ret; 88 89 directory = opendir(dir); 90 if (directory == NULL) { 91 if (errno != ENOENT) 92 return -errno; 93 else 94 return 0; 95 } 96 97 while ((ent = readdir(directory)) != NULL) { 98 if (!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, "..")) 99 continue; 100 len = strlen(dir) + strlen("/") + strlen(ent->d_name) + 1; 101 if (len > sizeof(file)) { 102 ret = -E2BIG; 103 goto out; 104 } 105 106 sprintf(file, "%s/%s", dir, ent->d_name); 107 if (unlink(file) < 0 && errno != ENOENT) { 108 ret = -errno; 109 goto out; 110 } 111 } 112 113 if (rmdir(dir) < 0 && errno != ENOENT) { 114 ret = -errno; 115 goto out; 116 } 117 118 ret = 0; 119 out: 120 closedir(directory); 121 return ret; 122 } 123 124 /* 125 * This says that there isn't already a user of the specified directory even if 126 * there are errors during the checking. This is because if these errors 127 * happen, the directory is unusable by the pre-existing UML, so we might as 128 * well take it over. This could happen either by 129 * the existing UML somehow corrupting its umid directory 130 * something other than UML sticking stuff in the directory 131 * this boot racing with a shutdown of the other UML 132 * In any of these cases, the directory isn't useful for anything else. 133 * 134 * Boolean return: 1 if in use, 0 otherwise. 135 */ 136 static inline int is_umdir_used(char *dir) 137 { 138 char pid[sizeof("nnnnnnnnn")], *end, *file; 139 int dead, fd, p, n, err; 140 size_t filelen = strlen(dir) + sizeof("/pid") + 1; 141 142 file = malloc(filelen); 143 if (!file) 144 return -ENOMEM; 145 146 snprintf(file, filelen, "%s/pid", dir); 147 148 dead = 0; 149 fd = open(file, O_RDONLY); 150 if (fd < 0) { 151 fd = -errno; 152 if (fd != -ENOENT) { 153 printk(UM_KERN_ERR "is_umdir_used : couldn't open pid " 154 "file '%s', err = %d\n", file, -fd); 155 } 156 goto out; 157 } 158 159 err = 0; 160 n = read(fd, pid, sizeof(pid)); 161 if (n < 0) { 162 printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file " 163 "'%s', err = %d\n", file, errno); 164 goto out_close; 165 } else if (n == 0) { 166 printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file " 167 "'%s', 0-byte read\n", file); 168 goto out_close; 169 } 170 171 p = strtoul(pid, &end, 0); 172 if (end == pid) { 173 printk(UM_KERN_ERR "is_umdir_used : couldn't parse pid file " 174 "'%s', errno = %d\n", file, errno); 175 goto out_close; 176 } 177 178 if ((kill(p, 0) == 0) || (errno != ESRCH)) { 179 printk(UM_KERN_ERR "umid \"%s\" is already in use by pid %d\n", 180 umid, p); 181 return 1; 182 } 183 184 out_close: 185 close(fd); 186 out: 187 free(file); 188 return 0; 189 } 190 191 /* 192 * Try to remove the directory @dir unless it's in use. 193 * Precondition: @dir exists. 194 * Returns 0 for success, < 0 for failure in removal or if the directory is in 195 * use. 196 */ 197 static int umdir_take_if_dead(char *dir) 198 { 199 int ret; 200 if (is_umdir_used(dir)) 201 return -EEXIST; 202 203 ret = remove_files_and_dir(dir); 204 if (ret) { 205 printk(UM_KERN_ERR "is_umdir_used - remove_files_and_dir " 206 "failed with err = %d\n", ret); 207 } 208 return ret; 209 } 210 211 static void __init create_pid_file(void) 212 { 213 char pid[sizeof("nnnnnnnnn")], *file; 214 int fd, n; 215 216 n = strlen(uml_dir) + UMID_LEN + sizeof("/pid"); 217 file = malloc(n); 218 if (!file) 219 return; 220 221 if (umid_file_name("pid", file, n)) 222 goto out; 223 224 fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644); 225 if (fd < 0) { 226 printk(UM_KERN_ERR "Open of machine pid file \"%s\" failed: " 227 "%s\n", file, strerror(errno)); 228 goto out; 229 } 230 231 snprintf(pid, sizeof(pid), "%d\n", getpid()); 232 n = write(fd, pid, strlen(pid)); 233 if (n != strlen(pid)) 234 printk(UM_KERN_ERR "Write of pid file failed - err = %d\n", 235 errno); 236 237 close(fd); 238 out: 239 free(file); 240 } 241 242 int __init set_umid(char *name) 243 { 244 if (strlen(name) > UMID_LEN - 1) 245 return -E2BIG; 246 247 strlcpy(umid, name, sizeof(umid)); 248 249 return 0; 250 } 251 252 /* Changed in make_umid, which is called during early boot */ 253 static int umid_setup = 0; 254 255 static int __init make_umid(void) 256 { 257 int fd, err; 258 char tmp[256]; 259 260 if (umid_setup) 261 return 0; 262 263 make_uml_dir(); 264 265 if (*umid == '\0') { 266 strlcpy(tmp, uml_dir, sizeof(tmp)); 267 strlcat(tmp, "XXXXXX", sizeof(tmp)); 268 fd = mkstemp(tmp); 269 if (fd < 0) { 270 printk(UM_KERN_ERR "make_umid - mkstemp(%s) failed: " 271 "%s\n", tmp, strerror(errno)); 272 err = -errno; 273 goto err; 274 } 275 276 close(fd); 277 278 set_umid(&tmp[strlen(uml_dir)]); 279 280 /* 281 * There's a nice tiny little race between this unlink and 282 * the mkdir below. It'd be nice if there were a mkstemp 283 * for directories. 284 */ 285 if (unlink(tmp)) { 286 err = -errno; 287 goto err; 288 } 289 } 290 291 snprintf(tmp, sizeof(tmp), "%s%s", uml_dir, umid); 292 err = mkdir(tmp, 0777); 293 if (err < 0) { 294 err = -errno; 295 if (err != -EEXIST) 296 goto err; 297 298 if (umdir_take_if_dead(tmp) < 0) 299 goto err; 300 301 err = mkdir(tmp, 0777); 302 } 303 if (err) { 304 err = -errno; 305 printk(UM_KERN_ERR "Failed to create '%s' - err = %d\n", umid, 306 errno); 307 goto err; 308 } 309 310 umid_setup = 1; 311 312 create_pid_file(); 313 314 err = 0; 315 err: 316 return err; 317 } 318 319 static int __init make_umid_init(void) 320 { 321 if (!make_umid()) 322 return 0; 323 324 /* 325 * If initializing with the given umid failed, then try again with 326 * a random one. 327 */ 328 printk(UM_KERN_ERR "Failed to initialize umid \"%s\", trying with a " 329 "random umid\n", umid); 330 *umid = '\0'; 331 make_umid(); 332 333 return 0; 334 } 335 336 __initcall(make_umid_init); 337 338 int __init umid_file_name(char *name, char *buf, int len) 339 { 340 int n, err; 341 342 err = make_umid(); 343 if (err) 344 return err; 345 346 n = snprintf(buf, len, "%s%s/%s", uml_dir, umid, name); 347 if (n >= len) { 348 printk(UM_KERN_ERR "umid_file_name : buffer too short\n"); 349 return -E2BIG; 350 } 351 352 return 0; 353 } 354 355 char *get_umid(void) 356 { 357 return umid; 358 } 359 360 static int __init set_uml_dir(char *name, int *add) 361 { 362 if (*name == '\0') { 363 os_warn("uml_dir can't be an empty string\n"); 364 return 0; 365 } 366 367 if (name[strlen(name) - 1] == '/') { 368 uml_dir = name; 369 return 0; 370 } 371 372 uml_dir = malloc(strlen(name) + 2); 373 if (uml_dir == NULL) { 374 os_warn("Failed to malloc uml_dir - error = %d\n", errno); 375 376 /* 377 * Return 0 here because do_initcalls doesn't look at 378 * the return value. 379 */ 380 return 0; 381 } 382 sprintf(uml_dir, "%s/", name); 383 384 return 0; 385 } 386 387 __uml_setup("uml_dir=", set_uml_dir, 388 "uml_dir=<directory>\n" 389 " The location to place the pid and umid files.\n\n" 390 ); 391 392 static void remove_umid_dir(void) 393 { 394 char *dir, err; 395 396 dir = malloc(strlen(uml_dir) + UMID_LEN + 1); 397 if (!dir) 398 return; 399 400 sprintf(dir, "%s%s", uml_dir, umid); 401 err = remove_files_and_dir(dir); 402 if (err) 403 os_warn("%s - remove_files_and_dir failed with err = %d\n", 404 __func__, err); 405 406 free(dir); 407 } 408 409 __uml_exitcall(remove_umid_dir); 410