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.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 31 static 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 37 static int sys_memfd_create(const char *name, unsigned int flags) 38 { 39 return syscall(__NR_memfd_create, name, flags); 40 } 41 42 static int __child(int sk, int memfd) 43 { 44 int ret; 45 char buf; 46 47 /* 48 * Ensure we don't leave around a bunch of orphaned children if our 49 * tests fail. 50 */ 51 ret = prctl(PR_SET_PDEATHSIG, SIGKILL); 52 if (ret) { 53 fprintf(stderr, "%s: Child could not set DEATHSIG\n", 54 strerror(errno)); 55 return -1; 56 } 57 58 ret = send(sk, &memfd, sizeof(memfd), 0); 59 if (ret != sizeof(memfd)) { 60 fprintf(stderr, "%s: Child failed to send fd number\n", 61 strerror(errno)); 62 return -1; 63 } 64 65 /* 66 * The fixture setup is completed at this point. The tests will run. 67 * 68 * This blocking recv enables the parent to message the child. 69 * Either we will read 'P' off of the sk, indicating that we need 70 * to disable ptrace, or we will read a 0, indicating that the other 71 * side has closed the sk. This occurs during fixture teardown time, 72 * indicating that the child should exit. 73 */ 74 while ((ret = recv(sk, &buf, sizeof(buf), 0)) > 0) { 75 if (buf == 'P') { 76 ret = prctl(PR_SET_DUMPABLE, 0); 77 if (ret < 0) { 78 fprintf(stderr, 79 "%s: Child failed to disable ptrace\n", 80 strerror(errno)); 81 return -1; 82 } 83 } else { 84 fprintf(stderr, "Child received unknown command %c\n", 85 buf); 86 return -1; 87 } 88 ret = send(sk, &buf, sizeof(buf), 0); 89 if (ret != 1) { 90 fprintf(stderr, "%s: Child failed to ack\n", 91 strerror(errno)); 92 return -1; 93 } 94 } 95 if (ret < 0) { 96 fprintf(stderr, "%s: Child failed to read from socket\n", 97 strerror(errno)); 98 return -1; 99 } 100 101 return 0; 102 } 103 104 static int child(int sk) 105 { 106 int memfd, ret; 107 108 memfd = sys_memfd_create("test", 0); 109 if (memfd < 0) { 110 fprintf(stderr, "%s: Child could not create memfd\n", 111 strerror(errno)); 112 ret = -1; 113 } else { 114 ret = __child(sk, memfd); 115 close(memfd); 116 } 117 118 close(sk); 119 return ret; 120 } 121 122 FIXTURE(child) 123 { 124 /* 125 * remote_fd is the number of the FD which we are trying to retrieve 126 * from the child. 127 */ 128 int remote_fd; 129 /* pid points to the child which we are fetching FDs from */ 130 pid_t pid; 131 /* pidfd is the pidfd of the child */ 132 int pidfd; 133 /* 134 * sk is our side of the socketpair used to communicate with the child. 135 * When it is closed, the child will exit. 136 */ 137 int sk; 138 }; 139 140 FIXTURE_SETUP(child) 141 { 142 int ret, sk_pair[2]; 143 144 ASSERT_EQ(0, socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair)) { 145 TH_LOG("%s: failed to create socketpair", strerror(errno)); 146 } 147 self->sk = sk_pair[0]; 148 149 self->pid = fork(); 150 ASSERT_GE(self->pid, 0); 151 152 if (self->pid == 0) { 153 close(sk_pair[0]); 154 if (child(sk_pair[1])) 155 _exit(EXIT_FAILURE); 156 _exit(EXIT_SUCCESS); 157 } 158 159 close(sk_pair[1]); 160 161 self->pidfd = sys_pidfd_open(self->pid, 0); 162 ASSERT_GE(self->pidfd, 0); 163 164 /* 165 * Wait for the child to complete setup. It'll send the remote memfd's 166 * number when ready. 167 */ 168 ret = recv(sk_pair[0], &self->remote_fd, sizeof(self->remote_fd), 0); 169 ASSERT_EQ(sizeof(self->remote_fd), ret); 170 } 171 172 FIXTURE_TEARDOWN(child) 173 { 174 EXPECT_EQ(0, close(self->pidfd)); 175 EXPECT_EQ(0, close(self->sk)); 176 177 EXPECT_EQ(0, wait_for_pid(self->pid)); 178 } 179 180 TEST_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 } 205 206 TEST_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 EXPECT_EQ(0, sys_kcmp(getpid(), self->pid, KCMP_FILE, fd, self->remote_fd)); 214 215 ret = fcntl(fd, F_GETFD); 216 ASSERT_GE(ret, 0); 217 EXPECT_GE(ret & FD_CLOEXEC, 0); 218 219 close(fd); 220 } 221 222 TEST_F(child, test_unknown_fd) 223 { 224 int fd; 225 226 fd = sys_pidfd_getfd(self->pidfd, UNKNOWN_FD, 0); 227 EXPECT_EQ(-1, fd) { 228 TH_LOG("getfd succeeded while fetching unknown fd"); 229 }; 230 EXPECT_EQ(EBADF, errno) { 231 TH_LOG("%s: getfd did not get EBADF", strerror(errno)); 232 } 233 } 234 235 TEST(flags_set) 236 { 237 ASSERT_EQ(-1, sys_pidfd_getfd(0, 0, 1)); 238 EXPECT_EQ(errno, EINVAL); 239 } 240 241 #if __NR_pidfd_getfd == -1 242 int main(void) 243 { 244 fprintf(stderr, "__NR_pidfd_getfd undefined. The pidfd_getfd syscall is unavailable. Test aborting\n"); 245 return KSFT_SKIP; 246 } 247 #else 248 TEST_HARNESS_MAIN 249 #endif 250