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 */
23static char umid[UMID_LEN] = { 0 };
24
25/* Changed by set_uml_dir and make_uml_dir, which are run early in boot */
26static char *uml_dir = UML_DIR;
27
28static 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
68err_free:
69	free(uml_dir);
70err:
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 */
81static 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;
119out:
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 */
136static 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
183out_close:
184	close(fd);
185out:
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 */
196static 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
210static 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);
237out:
238	free(file);
239}
240
241int __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 */
252static int umid_setup = 0;
253
254static 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
318static 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
337int __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
354char *get_umid(void)
355{
356	return umid;
357}
358
359static 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
391static 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