1 /*
2  * Copyright (c) 2019 Stefan Sperling <stsp@openbsd.org>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <sys/stat.h>
18 
19 #include <errno.h>
20 #include <fcntl.h>
21 #include <stdlib.h>
22 #include <unistd.h>
23 #include <string.h>
24 #include <stdio.h>
25 #include <time.h>
26 
27 #include "got_error.h"
28 #include "got_path.h"
29 
30 #include "got_lib_lockfile.h"
31 
32 const struct got_error *
33 got_lockfile_lock(struct got_lockfile **lf, const char *path, int dir_fd)
34 {
35 	const struct got_error *err = NULL;
36 	int attempts = 5;
37 
38 	*lf = calloc(1, sizeof(**lf));
39 	if (*lf == NULL)
40 		return got_error_from_errno("calloc");
41 	(*lf)->fd = -1;
42 
43 	(*lf)->locked_path = strdup(path);
44 	if ((*lf)->locked_path == NULL) {
45 		err = got_error_from_errno("strdup");
46 		goto done;
47 	}
48 
49 	if (asprintf(&(*lf)->path, "%s%s", path, GOT_LOCKFILE_SUFFIX) == -1) {
50 		err = got_error_from_errno("asprintf");
51 		goto done;
52 	}
53 
54 	do {
55 		if (dir_fd != -1) {
56 			(*lf)->fd = openat(dir_fd, (*lf)->path,
57 			    O_RDONLY | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
58 			    GOT_DEFAULT_FILE_MODE);
59 		} else {
60 			(*lf)->fd = open((*lf)->path,
61 			    O_RDONLY | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
62 			    GOT_DEFAULT_FILE_MODE);
63 		}
64 		if ((*lf)->fd != -1)
65 			break;
66 		if (errno != EEXIST) {
67 			err = got_error_from_errno2("open", (*lf)->path);
68 			goto done;
69 		}
70 		sleep(1);
71 	} while (--attempts > 0);
72 
73 	if ((*lf)->fd == -1)
74 		err = got_error(GOT_ERR_LOCKFILE_TIMEOUT);
75 done:
76 	if (err) {
77 		got_lockfile_unlock(*lf, dir_fd);
78 		*lf = NULL;
79 	}
80 	return err;
81 }
82 
83 const struct got_error *
84 got_lockfile_unlock(struct got_lockfile *lf, int dir_fd)
85 {
86 	const struct got_error *err = NULL;
87 
88 	if (dir_fd != -1) {
89 		if (lf->path && lf->fd != -1 &&
90 		    unlinkat(dir_fd, lf->path, 0) != 0)
91 			err = got_error_from_errno("unlinkat");
92 	} else if (lf->path && lf->fd != -1 && unlink(lf->path) != 0)
93 		err = got_error_from_errno("unlink");
94 	if (lf->fd != -1 && close(lf->fd) == -1 && err == NULL)
95 		err = got_error_from_errno("close");
96 	free(lf->path);
97 	free(lf->locked_path);
98 	free(lf);
99 	return err;
100 }