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
make_uml_dir(void)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 strscpy(dir, home);
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 */
remove_files_and_dir(char * dir)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 */
is_umdir_used(char * dir)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 */
umdir_take_if_dead(char * dir)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
create_pid_file(void)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
set_umid(char * name)241 int __init set_umid(char *name)
242 {
243 if (strlen(name) > UMID_LEN - 1)
244 return -E2BIG;
245
246 strscpy(umid, name);
247
248 return 0;
249 }
250
251 /* Changed in make_umid, which is called during early boot */
252 static int umid_setup = 0;
253
make_umid(void)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 strscpy(tmp, uml_dir);
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
make_umid_init(void)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
umid_file_name(char * name,char * buf,int len)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
get_umid(void)354 char *get_umid(void)
355 {
356 return umid;
357 }
358
set_uml_dir(char * name,int * add)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
remove_umid_dir(void)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