1 /*
2  * Copyright (c) 2021 Alexey Dobriyan <adobriyan@gmail.com>
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  * Test that "mount -t proc -o subset=pid" hides everything but pids,
18  * /proc/self and /proc/thread-self.
19  */
20 #undef NDEBUG
21 #include <assert.h>
22 #include <errno.h>
23 #include <sched.h>
24 #include <stdbool.h>
25 #include <stdlib.h>
26 #include <string.h>
27 #include <sys/mount.h>
28 #include <sys/types.h>
29 #include <sys/stat.h>
30 #include <fcntl.h>
31 #include <dirent.h>
32 #include <unistd.h>
33 #include <stdio.h>
34 
35 static inline bool streq(const char *a, const char *b)
36 {
37 	return strcmp(a, b) == 0;
38 }
39 
40 static void make_private_proc(void)
41 {
42 	if (unshare(CLONE_NEWNS) == -1) {
43 		if (errno == ENOSYS || errno == EPERM) {
44 			exit(4);
45 		}
46 		exit(1);
47 	}
48 	if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) == -1) {
49 		exit(1);
50 	}
51 	if (mount(NULL, "/proc", "proc", 0, "subset=pid") == -1) {
52 		exit(1);
53 	}
54 }
55 
56 static bool string_is_pid(const char *s)
57 {
58 	while (1) {
59 		switch (*s++) {
60 		case '0':case '1':case '2':case '3':case '4':
61 		case '5':case '6':case '7':case '8':case '9':
62 			continue;
63 
64 		case '\0':
65 			return true;
66 
67 		default:
68 			return false;
69 		}
70 	}
71 }
72 
73 int main(void)
74 {
75 	make_private_proc();
76 
77 	DIR *d = opendir("/proc");
78 	assert(d);
79 
80 	struct dirent *de;
81 
82 	bool dot = false;
83 	bool dot_dot = false;
84 	bool self = false;
85 	bool thread_self = false;
86 
87 	while ((de = readdir(d))) {
88 		if (streq(de->d_name, ".")) {
89 			assert(!dot);
90 			dot = true;
91 			assert(de->d_type == DT_DIR);
92 		} else if (streq(de->d_name, "..")) {
93 			assert(!dot_dot);
94 			dot_dot = true;
95 			assert(de->d_type == DT_DIR);
96 		} else if (streq(de->d_name, "self")) {
97 			assert(!self);
98 			self = true;
99 			assert(de->d_type == DT_LNK);
100 		} else if (streq(de->d_name, "thread-self")) {
101 			assert(!thread_self);
102 			thread_self = true;
103 			assert(de->d_type == DT_LNK);
104 		} else {
105 			if (!string_is_pid(de->d_name)) {
106 				fprintf(stderr, "d_name '%s'\n", de->d_name);
107 				assert(0);
108 			}
109 			assert(de->d_type == DT_DIR);
110 		}
111 	}
112 
113 	char c;
114 	int rv = readlink("/proc/cpuinfo", &c, 1);
115 	assert(rv == -1 && errno == ENOENT);
116 
117 	int fd = open("/proc/cpuinfo", O_RDONLY);
118 	assert(fd == -1 && errno == ENOENT);
119 
120 	return 0;
121 }
122