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 "got_compat.h"
18 
19 #include <sys/stat.h>
20 #include <sys/queue.h>
21 
22 #include <errno.h>
23 #include <fcntl.h>
24 #include <stdlib.h>
25 #include <unistd.h>
26 #include <string.h>
27 #include <stdio.h>
28 #include <time.h>
29 
30 #include "got_error.h"
31 #include "got_path.h"
32 
33 #include "got_lib_lockfile.h"
34 
35 const struct got_error *
36 got_lockfile_lock(struct got_lockfile **lf, const char *path, int dir_fd)
37 {
38 	const struct got_error *err = NULL;
39 	int attempts = 5;
40 
41 	*lf = calloc(1, sizeof(**lf));
42 	if (*lf == NULL)
43 		return got_error_from_errno("calloc");
44 	(*lf)->fd = -1;
45 
46 	(*lf)->locked_path = strdup(path);
47 	if ((*lf)->locked_path == NULL) {
48 		err = got_error_from_errno("strdup");
49 		goto done;
50 	}
51 
52 	if (asprintf(&(*lf)->path, "%s%s", path, GOT_LOCKFILE_SUFFIX) == -1) {
53 		err = got_error_from_errno("asprintf");
54 		goto done;
55 	}
56 
57 	do {
58 		if (dir_fd != -1) {
59 			(*lf)->fd = openat(dir_fd, (*lf)->path,
60 			    O_RDWR | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
61 			    GOT_DEFAULT_FILE_MODE);
62 		} else {
63 			(*lf)->fd = open((*lf)->path,
64 			    O_RDWR | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
65 			    GOT_DEFAULT_FILE_MODE);
66 		}
67 		if ((*lf)->fd != -1)
68 			break;
69 		if (errno != EEXIST) {
70 			err = got_error_from_errno2("open", (*lf)->path);
71 			goto done;
72 		}
73 		sleep(1);
74 	} while (--attempts > 0);
75 
76 	if ((*lf)->fd == -1) {
77 		err = got_error_fmt(GOT_ERR_LOCKFILE_TIMEOUT,
78 		    "%s", (*lf)->path);
79 	}
80 done:
81 	if (err) {
82 		got_lockfile_unlock(*lf, dir_fd);
83 		*lf = NULL;
84 	}
85 	return err;
86 }
87 
88 const struct got_error *
89 got_lockfile_unlock(struct got_lockfile *lf, int dir_fd)
90 {
91 	const struct got_error *err = NULL;
92 
93 	if (dir_fd != -1) {
94 		if (lf->path && lf->fd != -1 &&
95 		    unlinkat(dir_fd, lf->path, 0) != 0)
96 			err = got_error_from_errno("unlinkat");
97 	} else if (lf->path && lf->fd != -1 && unlink(lf->path) != 0)
98 		err = got_error_from_errno("unlink");
99 	if (lf->fd != -1 && close(lf->fd) == -1 && err == NULL)
100 		err = got_error_from_errno("close");
101 	free(lf->path);
102 	free(lf->locked_path);
103 	free(lf);
104 	return err;
105 }