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 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 fd = open(file, O_RDONLY); 149 if (fd < 0) { 150 fd = -errno; 151 if (fd != -ENOENT) { 152 printk(UM_KERN_ERR "is_umdir_used : couldn't open pid " 153 "file '%s', err = %d\n", file, -fd); 154 } 155 goto out; 156 } 157 158 err = 0; 159 n = read(fd, pid, sizeof(pid)); 160 if (n < 0) { 161 printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file " 162 "'%s', err = %d\n", file, errno); 163 goto out_close; 164 } else if (n == 0) { 165 printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file " 166 "'%s', 0-byte read\n", file); 167 goto out_close; 168 } 169 170 p = strtoul(pid, &end, 0); 171 if (end == pid) { 172 printk(UM_KERN_ERR "is_umdir_used : couldn't parse pid file " 173 "'%s', errno = %d\n", file, errno); 174 goto out_close; 175 } 176 177 if ((kill(p, 0) == 0) || (errno != ESRCH)) { 178 printk(UM_KERN_ERR "umid \"%s\" is already in use by pid %d\n", 179 umid, p); 180 return 1; 181 } 182 183 out_close: 184 close(fd); 185 out: 186 free(file); 187 return 0; 188 } 189 190 /* 191 * Try to remove the directory @dir unless it's in use. 192 * Precondition: @dir exists. 193 * Returns 0 for success, < 0 for failure in removal or if the directory is in 194 * use. 195 */ 196 static int umdir_take_if_dead(char *dir) 197 { 198 int ret; 199 if (is_umdir_used(dir)) 200 return -EEXIST; 201 202 ret = remove_files_and_dir(dir); 203 if (ret) { 204 printk(UM_KERN_ERR "is_umdir_used - remove_files_and_dir " 205 "failed with err = %d\n", ret); 206 } 207 return ret; 208 } 209 210 static void __init create_pid_file(void) 211 { 212 char pid[sizeof("nnnnnnnnn")], *file; 213 int fd, n; 214 215 n = strlen(uml_dir) + UMID_LEN + sizeof("/pid"); 216 file = malloc(n); 217 if (!file) 218 return; 219 220 if (umid_file_name("pid", file, n)) 221 goto out; 222 223 fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644); 224 if (fd < 0) { 225 printk(UM_KERN_ERR "Open of machine pid file \"%s\" failed: " 226 "%s\n", file, strerror(errno)); 227 goto out; 228 } 229 230 snprintf(pid, sizeof(pid), "%d\n", getpid()); 231 n = write(fd, pid, strlen(pid)); 232 if (n != strlen(pid)) 233 printk(UM_KERN_ERR "Write of pid file failed - err = %d\n", 234 errno); 235 236 close(fd); 237 out: 238 free(file); 239 } 240 241 int __init set_umid(char *name) 242 { 243 if (strlen(name) > UMID_LEN - 1) 244 return -E2BIG; 245 246 strlcpy(umid, name, sizeof(umid)); 247 248 return 0; 249 } 250 251 /* Changed in make_umid, which is called during early boot */ 252 static int umid_setup = 0; 253 254 static int __init make_umid(void) 255 { 256 int fd, err; 257 char tmp[256]; 258 259 if (umid_setup) 260 return 0; 261 262 make_uml_dir(); 263 264 if (*umid == '\0') { 265 strlcpy(tmp, uml_dir, sizeof(tmp)); 266 strlcat(tmp, "XXXXXX", sizeof(tmp)); 267 fd = mkstemp(tmp); 268 if (fd < 0) { 269 printk(UM_KERN_ERR "make_umid - mkstemp(%s) failed: " 270 "%s\n", tmp, strerror(errno)); 271 err = -errno; 272 goto err; 273 } 274 275 close(fd); 276 277 set_umid(&tmp[strlen(uml_dir)]); 278 279 /* 280 * There's a nice tiny little race between this unlink and 281 * the mkdir below. It'd be nice if there were a mkstemp 282 * for directories. 283 */ 284 if (unlink(tmp)) { 285 err = -errno; 286 goto err; 287 } 288 } 289 290 snprintf(tmp, sizeof(tmp), "%s%s", uml_dir, umid); 291 err = mkdir(tmp, 0777); 292 if (err < 0) { 293 err = -errno; 294 if (err != -EEXIST) 295 goto err; 296 297 if (umdir_take_if_dead(tmp) < 0) 298 goto err; 299 300 err = mkdir(tmp, 0777); 301 } 302 if (err) { 303 err = -errno; 304 printk(UM_KERN_ERR "Failed to create '%s' - err = %d\n", umid, 305 errno); 306 goto err; 307 } 308 309 umid_setup = 1; 310 311 create_pid_file(); 312 313 err = 0; 314 err: 315 return err; 316 } 317 318 static int __init make_umid_init(void) 319 { 320 if (!make_umid()) 321 return 0; 322 323 /* 324 * If initializing with the given umid failed, then try again with 325 * a random one. 326 */ 327 printk(UM_KERN_ERR "Failed to initialize umid \"%s\", trying with a " 328 "random umid\n", umid); 329 *umid = '\0'; 330 make_umid(); 331 332 return 0; 333 } 334 335 __initcall(make_umid_init); 336 337 int __init umid_file_name(char *name, char *buf, int len) 338 { 339 int n, err; 340 341 err = make_umid(); 342 if (err) 343 return err; 344 345 n = snprintf(buf, len, "%s%s/%s", uml_dir, umid, name); 346 if (n >= len) { 347 printk(UM_KERN_ERR "umid_file_name : buffer too short\n"); 348 return -E2BIG; 349 } 350 351 return 0; 352 } 353 354 char *get_umid(void) 355 { 356 return umid; 357 } 358 359 static int __init set_uml_dir(char *name, int *add) 360 { 361 if (*name == '\0') { 362 os_warn("uml_dir can't be an empty string\n"); 363 return 0; 364 } 365 366 if (name[strlen(name) - 1] == '/') { 367 uml_dir = name; 368 return 0; 369 } 370 371 uml_dir = malloc(strlen(name) + 2); 372 if (uml_dir == NULL) { 373 os_warn("Failed to malloc uml_dir - error = %d\n", errno); 374 375 /* 376 * Return 0 here because do_initcalls doesn't look at 377 * the return value. 378 */ 379 return 0; 380 } 381 sprintf(uml_dir, "%s/", name); 382 383 return 0; 384 } 385 386 __uml_setup("uml_dir=", set_uml_dir, 387 "uml_dir=<directory>\n" 388 " The location to place the pid and umid files.\n\n" 389 ); 390 391 static void remove_umid_dir(void) 392 { 393 char *dir, err; 394 395 dir = malloc(strlen(uml_dir) + UMID_LEN + 1); 396 if (!dir) 397 return; 398 399 sprintf(dir, "%s%s", uml_dir, umid); 400 err = remove_files_and_dir(dir); 401 if (err) 402 os_warn("%s - remove_files_and_dir failed with err = %d\n", 403 __func__, err); 404 405 free(dir); 406 } 407 408 __uml_exitcall(remove_umid_dir); 409