summaryrefslogtreecommitdiff
path: root/tools/testing/selftests/pidfd/pidfd_getfd_test.c
blob: 0930e2411dfb9a1337988e4cb815e14bfa4464b5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
// SPDX-License-Identifier: GPL-2.0

#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <linux/types.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syscall.h>
#include <sys/prctl.h>
#include <sys/wait.h>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/kcmp.h>

#include "pidfd.h"
#include "../kselftest_harness.h"

/*
 * UNKNOWN_FD is an fd number that should never exist in the child, as it is
 * used to check the negative case.
 */
#define UNKNOWN_FD 111
#define UID_NOBODY 65535

static int sys_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1,
		    unsigned long idx2)
{
	return syscall(__NR_kcmp, pid1, pid2, type, idx1, idx2);
}

static int __child(int sk, int memfd)
{
	int ret;
	char buf;

	/*
	 * Ensure we don't leave around a bunch of orphaned children if our
	 * tests fail.
	 */
	ret = prctl(PR_SET_PDEATHSIG, SIGKILL);
	if (ret) {
		fprintf(stderr, "%s: Child could not set DEATHSIG\n",
			strerror(errno));
		return -1;
	}

	ret = send(sk, &memfd, sizeof(memfd), 0);
	if (ret != sizeof(memfd)) {
		fprintf(stderr, "%s: Child failed to send fd number\n",
			strerror(errno));
		return -1;
	}

	/*
	 * The fixture setup is completed at this point. The tests will run.
	 *
	 * This blocking recv enables the parent to message the child.
	 * Either we will read 'P' off of the sk, indicating that we need
	 * to disable ptrace, or we will read a 0, indicating that the other
	 * side has closed the sk. This occurs during fixture teardown time,
	 * indicating that the child should exit.
	 */
	while ((ret = recv(sk, &buf, sizeof(buf), 0)) > 0) {
		if (buf == 'P') {
			ret = prctl(PR_SET_DUMPABLE, 0);
			if (ret < 0) {
				fprintf(stderr,
					"%s: Child failed to disable ptrace\n",
					strerror(errno));
				return -1;
			}
		} else {
			fprintf(stderr, "Child received unknown command %c\n",
				buf);
			return -1;
		}
		ret = send(sk, &buf, sizeof(buf), 0);
		if (ret != 1) {
			fprintf(stderr, "%s: Child failed to ack\n",
				strerror(errno));
			return -1;
		}
	}
	if (ret < 0) {
		fprintf(stderr, "%s: Child failed to read from socket\n",
			strerror(errno));
		return -1;
	}

	return 0;
}

static int child(int sk)
{
	int memfd, ret;

	memfd = sys_memfd_create("test", 0);
	if (memfd < 0) {
		fprintf(stderr, "%s: Child could not create memfd\n",
			strerror(errno));
		ret = -1;
	} else {
		ret = __child(sk, memfd);
		close(memfd);
	}

	close(sk);
	return ret;
}

FIXTURE(child)
{
	/*
	 * remote_fd is the number of the FD which we are trying to retrieve
	 * from the child.
	 */
	int remote_fd;
	/* pid points to the child which we are fetching FDs from */
	pid_t pid;
	/* pidfd is the pidfd of the child */
	int pidfd;
	/*
	 * sk is our side of the socketpair used to communicate with the child.
	 * When it is closed, the child will exit.
	 */
	int sk;
};

FIXTURE_SETUP(child)
{
	int ret, sk_pair[2];

	ASSERT_EQ(0, socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair)) {
		TH_LOG("%s: failed to create socketpair", strerror(errno));
	}
	self->sk = sk_pair[0];

	self->pid = fork();
	ASSERT_GE(self->pid, 0);

	if (self->pid == 0) {
		close(sk_pair[0]);
		if (child(sk_pair[1]))
			_exit(EXIT_FAILURE);
		_exit(EXIT_SUCCESS);
	}

	close(sk_pair[1]);

	self->pidfd = sys_pidfd_open(self->pid, 0);
	ASSERT_GE(self->pidfd, 0);

	/*
	 * Wait for the child to complete setup. It'll send the remote memfd's
	 * number when ready.
	 */
	ret = recv(sk_pair[0], &self->remote_fd, sizeof(self->remote_fd), 0);
	ASSERT_EQ(sizeof(self->remote_fd), ret);
}

FIXTURE_TEARDOWN(child)
{
	EXPECT_EQ(0, close(self->pidfd));
	EXPECT_EQ(0, close(self->sk));

	EXPECT_EQ(0, wait_for_pid(self->pid));
}

TEST_F(child, disable_ptrace)
{
	int uid, fd;
	char c;

	/*
	 * Turn into nobody if we're root, to avoid CAP_SYS_PTRACE
	 *
	 * The tests should run in their own process, so even this test fails,
	 * it shouldn't result in subsequent tests failing.
	 */
	uid = getuid();
	if (uid == 0)
		ASSERT_EQ(0, seteuid(UID_NOBODY));

	ASSERT_EQ(1, send(self->sk, "P", 1, 0));
	ASSERT_EQ(1, recv(self->sk, &c, 1, 0));

	fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);
	EXPECT_EQ(-1, fd);
	EXPECT_EQ(EPERM, errno);

	if (uid == 0)
		ASSERT_EQ(0, seteuid(0));
}

TEST_F(child, fetch_fd)
{
	int fd, ret;

	fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);
	ASSERT_GE(fd, 0);

	ret = sys_kcmp(getpid(), self->pid, KCMP_FILE, fd, self->remote_fd);
	if (ret < 0 && errno == ENOSYS)
		SKIP(return, "kcmp() syscall not supported");
	EXPECT_EQ(ret, 0);

	ret = fcntl(fd, F_GETFD);
	ASSERT_GE(ret, 0);
	EXPECT_GE(ret & FD_CLOEXEC, 0);

	close(fd);
}

TEST_F(child, test_unknown_fd)
{
	int fd;

	fd = sys_pidfd_getfd(self->pidfd, UNKNOWN_FD, 0);
	EXPECT_EQ(-1, fd) {
		TH_LOG("getfd succeeded while fetching unknown fd");
	};
	EXPECT_EQ(EBADF, errno) {
		TH_LOG("%s: getfd did not get EBADF", strerror(errno));
	}
}

TEST(flags_set)
{
	ASSERT_EQ(-1, sys_pidfd_getfd(0, 0, 1));
	EXPECT_EQ(errno, EINVAL);
}

#if __NR_pidfd_getfd == -1
int main(void)
{
	fprintf(stderr, "__NR_pidfd_getfd undefined. The pidfd_getfd syscall is unavailable. Test aborting\n");
	return KSFT_SKIP;
}
#else
TEST_HARNESS_MAIN
#endif