xref: /linux/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c (revision d677aebd663ddc287f2b2bda098474694a0ca875)
1 // SPDX-License-Identifier: GPL-2.0
2 
3 /*
4  * Based on Christian Brauner's clone3() example.
5  * These tests are assuming to be running in the host's
6  * PID namespace.
7  */
8 
9 /* capabilities related code based on selftests/bpf/test_verifier.c */
10 
11 #define _GNU_SOURCE
12 #include <errno.h>
13 #include <linux/types.h>
14 #include <linux/sched.h>
15 #include <stdio.h>
16 #include <stdlib.h>
17 #include <stdbool.h>
18 #include <sys/capability.h>
19 #include <sys/prctl.h>
20 #include <sys/syscall.h>
21 #include <sys/types.h>
22 #include <sys/un.h>
23 #include <sys/wait.h>
24 #include <unistd.h>
25 #include <sched.h>
26 
27 #include "../kselftest_harness.h"
28 #include "clone3_selftests.h"
29 
30 static void child_exit(int ret)
31 {
32 	fflush(stdout);
33 	fflush(stderr);
34 	_exit(ret);
35 }
36 
37 static int call_clone3_set_tid(struct __test_metadata *_metadata,
38 			       pid_t *set_tid, size_t set_tid_size)
39 {
40 	int status;
41 	pid_t pid = -1;
42 
43 	struct __clone_args args = {
44 		.exit_signal = SIGCHLD,
45 		.set_tid = ptr_to_u64(set_tid),
46 		.set_tid_size = set_tid_size,
47 	};
48 
49 	pid = sys_clone3(&args, sizeof(args));
50 	if (pid < 0) {
51 		TH_LOG("%s - Failed to create new process", strerror(errno));
52 		return -errno;
53 	}
54 
55 	if (pid == 0) {
56 		int ret;
57 		char tmp = 0;
58 
59 		TH_LOG("I am the child, my PID is %d (expected %d)", getpid(), set_tid[0]);
60 
61 		if (set_tid[0] != getpid())
62 			child_exit(EXIT_FAILURE);
63 		child_exit(EXIT_SUCCESS);
64 	}
65 
66 	TH_LOG("I am the parent (%d). My child's pid is %d", getpid(), pid);
67 
68 	if (waitpid(pid, &status, 0) < 0) {
69 		TH_LOG("Child returned %s", strerror(errno));
70 		return -errno;
71 	}
72 
73 	if (!WIFEXITED(status))
74 		return -1;
75 
76 	return WEXITSTATUS(status);
77 }
78 
79 static int test_clone3_set_tid(struct __test_metadata *_metadata,
80 			       pid_t *set_tid, size_t set_tid_size)
81 {
82 	int ret;
83 
84 	TH_LOG("[%d] Trying clone3() with CLONE_SET_TID to %d", getpid(), set_tid[0]);
85 	ret = call_clone3_set_tid(_metadata, set_tid, set_tid_size);
86 	TH_LOG("[%d] clone3() with CLONE_SET_TID %d says:%d", getpid(), set_tid[0], ret);
87 	return ret;
88 }
89 
90 struct libcap {
91 	struct __user_cap_header_struct hdr;
92 	struct __user_cap_data_struct data[2];
93 };
94 
95 static int set_capability(void)
96 {
97 	cap_value_t cap_values[] = { CAP_SETUID, CAP_SETGID };
98 	struct libcap *cap;
99 	int ret = -1;
100 	cap_t caps;
101 
102 	caps = cap_get_proc();
103 	if (!caps) {
104 		perror("cap_get_proc");
105 		return -1;
106 	}
107 
108 	/* Drop all capabilities */
109 	if (cap_clear(caps)) {
110 		perror("cap_clear");
111 		goto out;
112 	}
113 
114 	cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_values, CAP_SET);
115 	cap_set_flag(caps, CAP_PERMITTED, 2, cap_values, CAP_SET);
116 
117 	cap = (struct libcap *) caps;
118 
119 	/* 40 -> CAP_CHECKPOINT_RESTORE */
120 	cap->data[1].effective |= 1 << (40 - 32);
121 	cap->data[1].permitted |= 1 << (40 - 32);
122 
123 	if (cap_set_proc(caps)) {
124 		perror("cap_set_proc");
125 		goto out;
126 	}
127 	ret = 0;
128 out:
129 	if (cap_free(caps))
130 		perror("cap_free");
131 	return ret;
132 }
133 
134 TEST(clone3_cap_checkpoint_restore)
135 {
136 	pid_t pid;
137 	int status;
138 	int ret = 0;
139 	pid_t set_tid[1];
140 
141 	test_clone3_supported();
142 
143 	EXPECT_EQ(getuid(), 0)
144 		SKIP(return, "Skipping all tests as non-root");
145 
146 	memset(&set_tid, 0, sizeof(set_tid));
147 
148 	/* Find the current active PID */
149 	pid = fork();
150 	if (pid == 0) {
151 		TH_LOG("Child has PID %d", getpid());
152 		child_exit(EXIT_SUCCESS);
153 	}
154 	ASSERT_GT(waitpid(pid, &status, 0), 0)
155 		TH_LOG("Waiting for child %d failed", pid);
156 
157 	/* After the child has finished, its PID should be free. */
158 	set_tid[0] = pid;
159 
160 	ASSERT_EQ(set_capability(), 0)
161 		TH_LOG("Could not set CAP_CHECKPOINT_RESTORE");
162 
163 	ASSERT_EQ(prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0), 0);
164 
165 	EXPECT_EQ(setgid(65534), 0)
166 		TH_LOG("Failed to setgid(65534)");
167 	ASSERT_EQ(setuid(65534), 0);
168 
169 	set_tid[0] = pid;
170 	/* This would fail without CAP_CHECKPOINT_RESTORE */
171 	ASSERT_EQ(test_clone3_set_tid(_metadata, set_tid, 1), -EPERM);
172 	ASSERT_EQ(set_capability(), 0)
173 		TH_LOG("Could not set CAP_CHECKPOINT_RESTORE");
174 	/* This should work as we have CAP_CHECKPOINT_RESTORE as non-root */
175 	ASSERT_EQ(test_clone3_set_tid(_metadata, set_tid, 1), 0);
176 }
177 
178 TEST_HARNESS_MAIN
179