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1// SPDX-License-Identifier: GPL-2.0
2
3#define _GNU_SOURCE
4#include <errno.h>
5#include <fcntl.h>
6#include <limits.h>
7#include <linux/types.h>
8#include <poll.h>
9#include <sched.h>
10#include <signal.h>
11#include <stdio.h>
12#include <stdlib.h>
13#include <string.h>
14#include <syscall.h>
15#include <sys/prctl.h>
16#include <sys/wait.h>
17#include <unistd.h>
18#include <sys/socket.h>
19#include <linux/kcmp.h>
20
21#include "pidfd.h"
22#include "kselftest_harness.h"
23
24/*
25 * UNKNOWN_FD is an fd number that should never exist in the child, as it is
26 * used to check the negative case.
27 */
28#define UNKNOWN_FD 111
29#define UID_NOBODY 65535
30
31static int sys_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1,
32 unsigned long idx2)
33{
34 return syscall(__NR_kcmp, pid1, pid2, type, idx1, idx2);
35}
36
37static int __child(int sk, int memfd)
38{
39 int ret;
40 char buf;
41
42 /*
43 * Ensure we don't leave around a bunch of orphaned children if our
44 * tests fail.
45 */
46 ret = prctl(PR_SET_PDEATHSIG, SIGKILL);
47 if (ret) {
48 fprintf(stderr, "%s: Child could not set DEATHSIG\n",
49 strerror(errno));
50 return -1;
51 }
52
53 ret = send(sk, &memfd, sizeof(memfd), 0);
54 if (ret != sizeof(memfd)) {
55 fprintf(stderr, "%s: Child failed to send fd number\n",
56 strerror(errno));
57 return -1;
58 }
59
60 /*
61 * The fixture setup is completed at this point. The tests will run.
62 *
63 * This blocking recv enables the parent to message the child.
64 * Either we will read 'P' off of the sk, indicating that we need
65 * to disable ptrace, or we will read a 0, indicating that the other
66 * side has closed the sk. This occurs during fixture teardown time,
67 * indicating that the child should exit.
68 */
69 while ((ret = recv(sk, &buf, sizeof(buf), 0)) > 0) {
70 if (buf == 'P') {
71 ret = prctl(PR_SET_DUMPABLE, 0);
72 if (ret < 0) {
73 fprintf(stderr,
74 "%s: Child failed to disable ptrace\n",
75 strerror(errno));
76 return -1;
77 }
78 } else {
79 fprintf(stderr, "Child received unknown command %c\n",
80 buf);
81 return -1;
82 }
83 ret = send(sk, &buf, sizeof(buf), 0);
84 if (ret != 1) {
85 fprintf(stderr, "%s: Child failed to ack\n",
86 strerror(errno));
87 return -1;
88 }
89 }
90 if (ret < 0) {
91 fprintf(stderr, "%s: Child failed to read from socket\n",
92 strerror(errno));
93 return -1;
94 }
95
96 return 0;
97}
98
99static int child(int sk)
100{
101 int memfd, ret;
102
103 memfd = sys_memfd_create("test", 0);
104 if (memfd < 0) {
105 fprintf(stderr, "%s: Child could not create memfd\n",
106 strerror(errno));
107 ret = -1;
108 } else {
109 ret = __child(sk, memfd);
110 close(memfd);
111 }
112
113 close(sk);
114 return ret;
115}
116
117FIXTURE(child)
118{
119 /*
120 * remote_fd is the number of the FD which we are trying to retrieve
121 * from the child.
122 */
123 int remote_fd;
124 /* pid points to the child which we are fetching FDs from */
125 pid_t pid;
126 /* pidfd is the pidfd of the child */
127 int pidfd;
128 /*
129 * sk is our side of the socketpair used to communicate with the child.
130 * When it is closed, the child will exit.
131 */
132 int sk;
133 bool ignore_child_result;
134};
135
136FIXTURE_SETUP(child)
137{
138 int ret, sk_pair[2];
139
140 ASSERT_EQ(0, socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair)) {
141 TH_LOG("%s: failed to create socketpair", strerror(errno));
142 }
143 self->sk = sk_pair[0];
144
145 self->pid = fork();
146 ASSERT_GE(self->pid, 0);
147
148 if (self->pid == 0) {
149 close(sk_pair[0]);
150 if (child(sk_pair[1]))
151 _exit(EXIT_FAILURE);
152 _exit(EXIT_SUCCESS);
153 }
154
155 close(sk_pair[1]);
156
157 self->pidfd = sys_pidfd_open(self->pid, 0);
158 ASSERT_GE(self->pidfd, 0);
159
160 /*
161 * Wait for the child to complete setup. It'll send the remote memfd's
162 * number when ready.
163 */
164 ret = recv(sk_pair[0], &self->remote_fd, sizeof(self->remote_fd), 0);
165 ASSERT_EQ(sizeof(self->remote_fd), ret);
166}
167
168FIXTURE_TEARDOWN(child)
169{
170 int ret;
171
172 EXPECT_EQ(0, close(self->pidfd));
173 EXPECT_EQ(0, close(self->sk));
174
175 ret = wait_for_pid(self->pid);
176 if (!self->ignore_child_result)
177 EXPECT_EQ(0, ret);
178}
179
180TEST_F(child, disable_ptrace)
181{
182 int uid, fd;
183 char c;
184
185 /*
186 * Turn into nobody if we're root, to avoid CAP_SYS_PTRACE
187 *
188 * The tests should run in their own process, so even this test fails,
189 * it shouldn't result in subsequent tests failing.
190 */
191 uid = getuid();
192 if (uid == 0)
193 ASSERT_EQ(0, seteuid(UID_NOBODY));
194
195 ASSERT_EQ(1, send(self->sk, "P", 1, 0));
196 ASSERT_EQ(1, recv(self->sk, &c, 1, 0));
197
198 fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);
199 EXPECT_EQ(-1, fd);
200 EXPECT_EQ(EPERM, errno);
201
202 if (uid == 0)
203 ASSERT_EQ(0, seteuid(0));
204}
205
206TEST_F(child, fetch_fd)
207{
208 int fd, ret;
209
210 fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);
211 ASSERT_GE(fd, 0);
212
213 ret = sys_kcmp(getpid(), self->pid, KCMP_FILE, fd, self->remote_fd);
214 if (ret < 0 && errno == ENOSYS)
215 SKIP(return, "kcmp() syscall not supported");
216 EXPECT_EQ(ret, 0);
217
218 ret = fcntl(fd, F_GETFD);
219 ASSERT_GE(ret, 0);
220 EXPECT_GE(ret & FD_CLOEXEC, 0);
221
222 close(fd);
223}
224
225TEST_F(child, test_unknown_fd)
226{
227 int fd;
228
229 fd = sys_pidfd_getfd(self->pidfd, UNKNOWN_FD, 0);
230 EXPECT_EQ(-1, fd) {
231 TH_LOG("getfd succeeded while fetching unknown fd");
232 };
233 EXPECT_EQ(EBADF, errno) {
234 TH_LOG("%s: getfd did not get EBADF", strerror(errno));
235 }
236}
237
238TEST(flags_set)
239{
240 ASSERT_EQ(-1, sys_pidfd_getfd(0, 0, 1));
241 EXPECT_EQ(errno, EINVAL);
242}
243
244TEST_F(child, no_strange_EBADF)
245{
246 struct pollfd fds;
247
248 self->ignore_child_result = true;
249
250 fds.fd = self->pidfd;
251 fds.events = POLLIN;
252
253 ASSERT_EQ(kill(self->pid, SIGKILL), 0);
254 ASSERT_EQ(poll(&fds, 1, 5000), 1);
255
256 /*
257 * It used to be that pidfd_getfd() could race with the exiting thread
258 * between exit_files() and release_task(), and get a non-null task
259 * with a NULL files struct, and you'd get EBADF, which was slightly
260 * confusing.
261 */
262 errno = 0;
263 EXPECT_EQ(sys_pidfd_getfd(self->pidfd, self->remote_fd, 0), -1);
264 EXPECT_EQ(errno, ESRCH);
265}
266
267#if __NR_pidfd_getfd == -1
268int main(void)
269{
270 fprintf(stderr, "__NR_pidfd_getfd undefined. The pidfd_getfd syscall is unavailable. Test aborting\n");
271 return KSFT_SKIP;
272}
273#else
274TEST_HARNESS_MAIN
275#endif