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) + sizeof("/") + 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("nnnnn\0")], *end, *file; 139 int dead, fd, p, n, err; 140 size_t filelen; 141 142 err = asprintf(&file, "%s/pid", dir); 143 if (err < 0) 144 return 0; 145 146 filelen = strlen(file); 147 148 n = snprintf(file, filelen, "%s/pid", dir); 149 if (n >= filelen) { 150 printk(UM_KERN_ERR "is_umdir_used - pid filename too long\n"); 151 err = -E2BIG; 152 goto out; 153 } 154 155 dead = 0; 156 fd = open(file, O_RDONLY); 157 if (fd < 0) { 158 fd = -errno; 159 if (fd != -ENOENT) { 160 printk(UM_KERN_ERR "is_umdir_used : couldn't open pid " 161 "file '%s', err = %d\n", file, -fd); 162 } 163 goto out; 164 } 165 166 err = 0; 167 n = read(fd, pid, sizeof(pid)); 168 if (n < 0) { 169 printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file " 170 "'%s', err = %d\n", file, errno); 171 goto out_close; 172 } else if (n == 0) { 173 printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file " 174 "'%s', 0-byte read\n", file); 175 goto out_close; 176 } 177 178 p = strtoul(pid, &end, 0); 179 if (end == pid) { 180 printk(UM_KERN_ERR "is_umdir_used : couldn't parse pid file " 181 "'%s', errno = %d\n", file, errno); 182 goto out_close; 183 } 184 185 if ((kill(p, 0) == 0) || (errno != ESRCH)) { 186 printk(UM_KERN_ERR "umid \"%s\" is already in use by pid %d\n", 187 umid, p); 188 return 1; 189 } 190 191 out_close: 192 close(fd); 193 out: 194 free(file); 195 return 0; 196 } 197 198 /* 199 * Try to remove the directory @dir unless it's in use. 200 * Precondition: @dir exists. 201 * Returns 0 for success, < 0 for failure in removal or if the directory is in 202 * use. 203 */ 204 static int umdir_take_if_dead(char *dir) 205 { 206 int ret; 207 if (is_umdir_used(dir)) 208 return -EEXIST; 209 210 ret = remove_files_and_dir(dir); 211 if (ret) { 212 printk(UM_KERN_ERR "is_umdir_used - remove_files_and_dir " 213 "failed with err = %d\n", ret); 214 } 215 return ret; 216 } 217 218 static void __init create_pid_file(void) 219 { 220 char pid[sizeof("nnnnn\0")], *file; 221 int fd, n; 222 223 file = malloc(strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")); 224 if (!file) 225 return; 226 227 if (umid_file_name("pid", file, sizeof(file))) 228 goto out; 229 230 fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644); 231 if (fd < 0) { 232 printk(UM_KERN_ERR "Open of machine pid file \"%s\" failed: " 233 "%s\n", file, strerror(errno)); 234 goto out; 235 } 236 237 snprintf(pid, sizeof(pid), "%d\n", getpid()); 238 n = write(fd, pid, strlen(pid)); 239 if (n != strlen(pid)) 240 printk(UM_KERN_ERR "Write of pid file failed - err = %d\n", 241 errno); 242 243 close(fd); 244 out: 245 free(file); 246 } 247 248 int __init set_umid(char *name) 249 { 250 if (strlen(name) > UMID_LEN - 1) 251 return -E2BIG; 252 253 strlcpy(umid, name, sizeof(umid)); 254 255 return 0; 256 } 257 258 /* Changed in make_umid, which is called during early boot */ 259 static int umid_setup = 0; 260 261 static int __init make_umid(void) 262 { 263 int fd, err; 264 char tmp[256]; 265 266 if (umid_setup) 267 return 0; 268 269 make_uml_dir(); 270 271 if (*umid == '\0') { 272 strlcpy(tmp, uml_dir, sizeof(tmp)); 273 strlcat(tmp, "XXXXXX", sizeof(tmp)); 274 fd = mkstemp(tmp); 275 if (fd < 0) { 276 printk(UM_KERN_ERR "make_umid - mkstemp(%s) failed: " 277 "%s\n", tmp, strerror(errno)); 278 err = -errno; 279 goto err; 280 } 281 282 close(fd); 283 284 set_umid(&tmp[strlen(uml_dir)]); 285 286 /* 287 * There's a nice tiny little race between this unlink and 288 * the mkdir below. It'd be nice if there were a mkstemp 289 * for directories. 290 */ 291 if (unlink(tmp)) { 292 err = -errno; 293 goto err; 294 } 295 } 296 297 snprintf(tmp, sizeof(tmp), "%s%s", uml_dir, umid); 298 err = mkdir(tmp, 0777); 299 if (err < 0) { 300 err = -errno; 301 if (err != -EEXIST) 302 goto err; 303 304 if (umdir_take_if_dead(tmp) < 0) 305 goto err; 306 307 err = mkdir(tmp, 0777); 308 } 309 if (err) { 310 err = -errno; 311 printk(UM_KERN_ERR "Failed to create '%s' - err = %d\n", umid, 312 errno); 313 goto err; 314 } 315 316 umid_setup = 1; 317 318 create_pid_file(); 319 320 err = 0; 321 err: 322 return err; 323 } 324 325 static int __init make_umid_init(void) 326 { 327 if (!make_umid()) 328 return 0; 329 330 /* 331 * If initializing with the given umid failed, then try again with 332 * a random one. 333 */ 334 printk(UM_KERN_ERR "Failed to initialize umid \"%s\", trying with a " 335 "random umid\n", umid); 336 *umid = '\0'; 337 make_umid(); 338 339 return 0; 340 } 341 342 __initcall(make_umid_init); 343 344 int __init umid_file_name(char *name, char *buf, int len) 345 { 346 int n, err; 347 348 err = make_umid(); 349 if (err) 350 return err; 351 352 n = snprintf(buf, len, "%s%s/%s", uml_dir, umid, name); 353 if (n >= len) { 354 printk(UM_KERN_ERR "umid_file_name : buffer too short\n"); 355 return -E2BIG; 356 } 357 358 return 0; 359 } 360 361 char *get_umid(void) 362 { 363 return umid; 364 } 365 366 static int __init set_uml_dir(char *name, int *add) 367 { 368 if (*name == '\0') { 369 os_warn("uml_dir can't be an empty string\n"); 370 return 0; 371 } 372 373 if (name[strlen(name) - 1] == '/') { 374 uml_dir = name; 375 return 0; 376 } 377 378 uml_dir = malloc(strlen(name) + 2); 379 if (uml_dir == NULL) { 380 os_warn("Failed to malloc uml_dir - error = %d\n", errno); 381 382 /* 383 * Return 0 here because do_initcalls doesn't look at 384 * the return value. 385 */ 386 return 0; 387 } 388 sprintf(uml_dir, "%s/", name); 389 390 return 0; 391 } 392 393 __uml_setup("uml_dir=", set_uml_dir, 394 "uml_dir=<directory>\n" 395 " The location to place the pid and umid files.\n\n" 396 ); 397 398 static void remove_umid_dir(void) 399 { 400 char *dir, err; 401 402 dir = malloc(strlen(uml_dir) + UMID_LEN + 1); 403 if (!dir) 404 return; 405 406 sprintf(dir, "%s%s", uml_dir, umid); 407 err = remove_files_and_dir(dir); 408 if (err) 409 os_warn("%s - remove_files_and_dir failed with err = %d\n", 410 __func__, err); 411 412 free(dir); 413 } 414 415 __uml_exitcall(remove_umid_dir); 416