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