1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (c) 2014 Google, Inc. 4 * 5 * Selftests for execveat(2). 6 */ 7 8 #ifndef _GNU_SOURCE 9 #define _GNU_SOURCE /* to get O_PATH, AT_EMPTY_PATH */ 10 #endif 11 #include <sys/sendfile.h> 12 #include <sys/stat.h> 13 #include <sys/syscall.h> 14 #include <sys/types.h> 15 #include <sys/wait.h> 16 #include <errno.h> 17 #include <fcntl.h> 18 #include <limits.h> 19 #include <stdio.h> 20 #include <stdlib.h> 21 #include <string.h> 22 #include <unistd.h> 23 24 #include "../kselftest.h" 25 26 #define TESTS_EXPECTED 51 27 #define TEST_NAME_LEN (PATH_MAX * 4) 28 29 static char longpath[2 * PATH_MAX] = ""; 30 static char *envp[] = { "IN_TEST=yes", NULL, NULL }; 31 static char *argv[] = { "execveat", "99", NULL }; 32 33 static int execveat_(int fd, const char *path, char **argv, char **envp, 34 int flags) 35 { 36 #ifdef __NR_execveat 37 return syscall(__NR_execveat, fd, path, argv, envp, flags); 38 #else 39 errno = ENOSYS; 40 return -1; 41 #endif 42 } 43 44 #define check_execveat_fail(fd, path, flags, errno) \ 45 _check_execveat_fail(fd, path, flags, errno, #errno) 46 static int _check_execveat_fail(int fd, const char *path, int flags, 47 int expected_errno, const char *errno_str) 48 { 49 char test_name[TEST_NAME_LEN]; 50 int rc; 51 52 errno = 0; 53 snprintf(test_name, sizeof(test_name), 54 "Check failure of execveat(%d, '%s', %d) with %s", 55 fd, path?:"(null)", flags, errno_str); 56 rc = execveat_(fd, path, argv, envp, flags); 57 58 if (rc > 0) { 59 ksft_print_msg("unexpected success from execveat(2)\n"); 60 ksft_test_result_fail("%s\n", test_name); 61 return 1; 62 } 63 if (errno != expected_errno) { 64 ksft_print_msg("expected errno %d (%s) not %d (%s)\n", 65 expected_errno, strerror(expected_errno), 66 errno, strerror(errno)); 67 ksft_test_result_fail("%s\n", test_name); 68 return 1; 69 } 70 ksft_test_result_pass("%s\n", test_name); 71 return 0; 72 } 73 74 static int check_execveat_invoked_rc(int fd, const char *path, int flags, 75 int expected_rc, int expected_rc2) 76 { 77 char test_name[TEST_NAME_LEN]; 78 int status; 79 int rc; 80 pid_t child; 81 int pathlen = path ? strlen(path) : 0; 82 83 if (pathlen > 40) 84 snprintf(test_name, sizeof(test_name), 85 "Check success of execveat(%d, '%.20s...%s', %d)... ", 86 fd, path, (path + pathlen - 20), flags); 87 else 88 snprintf(test_name, sizeof(test_name), 89 "Check success of execveat(%d, '%s', %d)... ", 90 fd, path?:"(null)", flags); 91 92 child = fork(); 93 if (child < 0) { 94 ksft_perror("fork() failed"); 95 ksft_test_result_fail("%s\n", test_name); 96 return 1; 97 } 98 if (child == 0) { 99 /* Child: do execveat(). */ 100 rc = execveat_(fd, path, argv, envp, flags); 101 ksft_print_msg("execveat() failed, rc=%d errno=%d (%s)\n", 102 rc, errno, strerror(errno)); 103 ksft_test_result_fail("%s\n", test_name); 104 exit(1); /* should not reach here */ 105 } 106 /* Parent: wait for & check child's exit status. */ 107 rc = waitpid(child, &status, 0); 108 if (rc != child) { 109 ksft_print_msg("waitpid(%d,...) returned %d\n", child, rc); 110 ksft_test_result_fail("%s\n", test_name); 111 return 1; 112 } 113 if (!WIFEXITED(status)) { 114 ksft_print_msg("child %d did not exit cleanly, status=%08x\n", 115 child, status); 116 ksft_test_result_fail("%s\n", test_name); 117 return 1; 118 } 119 if ((WEXITSTATUS(status) != expected_rc) && 120 (WEXITSTATUS(status) != expected_rc2)) { 121 ksft_print_msg("child %d exited with %d not %d nor %d\n", 122 child, WEXITSTATUS(status), expected_rc, 123 expected_rc2); 124 ksft_test_result_fail("%s\n", test_name); 125 return 1; 126 } 127 ksft_test_result_pass("%s\n", test_name); 128 return 0; 129 } 130 131 static int check_execveat(int fd, const char *path, int flags) 132 { 133 return check_execveat_invoked_rc(fd, path, flags, 99, 99); 134 } 135 136 static char *concat(const char *left, const char *right) 137 { 138 char *result = malloc(strlen(left) + strlen(right) + 1); 139 140 strcpy(result, left); 141 strcat(result, right); 142 return result; 143 } 144 145 static int open_or_die(const char *filename, int flags) 146 { 147 int fd = open(filename, flags); 148 149 if (fd < 0) 150 ksft_exit_fail_msg("Failed to open '%s'; " 151 "check prerequisites are available\n", filename); 152 return fd; 153 } 154 155 static void exe_cp(const char *src, const char *dest) 156 { 157 int in_fd = open_or_die(src, O_RDONLY); 158 int out_fd = open(dest, O_RDWR|O_CREAT|O_TRUNC, 0755); 159 struct stat info; 160 161 fstat(in_fd, &info); 162 sendfile(out_fd, in_fd, NULL, info.st_size); 163 close(in_fd); 164 close(out_fd); 165 } 166 167 #define XX_DIR_LEN 200 168 static int check_execveat_pathmax(int root_dfd, const char *src, int is_script) 169 { 170 int fail = 0; 171 int ii, count, len; 172 char longname[XX_DIR_LEN + 1]; 173 int fd; 174 175 if (*longpath == '\0') { 176 /* Create a filename close to PATH_MAX in length */ 177 char *cwd = getcwd(NULL, 0); 178 179 if (!cwd) { 180 ksft_perror("Failed to getcwd()"); 181 return 2; 182 } 183 strcpy(longpath, cwd); 184 strcat(longpath, "/"); 185 memset(longname, 'x', XX_DIR_LEN - 1); 186 longname[XX_DIR_LEN - 1] = '/'; 187 longname[XX_DIR_LEN] = '\0'; 188 count = (PATH_MAX - 3 - strlen(cwd)) / XX_DIR_LEN; 189 for (ii = 0; ii < count; ii++) { 190 strcat(longpath, longname); 191 mkdir(longpath, 0755); 192 } 193 len = (PATH_MAX - 3 - strlen(cwd)) - (count * XX_DIR_LEN); 194 if (len <= 0) 195 len = 1; 196 memset(longname, 'y', len); 197 longname[len] = '\0'; 198 strcat(longpath, longname); 199 free(cwd); 200 } 201 exe_cp(src, longpath); 202 203 /* 204 * Execute as a pre-opened file descriptor, which works whether this is 205 * a script or not (because the interpreter sees a filename like 206 * "/dev/fd/20"). 207 */ 208 fd = open(longpath, O_RDONLY); 209 if (fd > 0) { 210 ksft_print_msg("Invoke copy of '%s' via filename of length %zu:\n", 211 src, strlen(longpath)); 212 fail += check_execveat(fd, "", AT_EMPTY_PATH); 213 } else { 214 ksft_print_msg("Failed to open length %zu filename, errno=%d (%s)\n", 215 strlen(longpath), errno, strerror(errno)); 216 fail++; 217 } 218 219 /* 220 * Execute as a long pathname relative to "/". If this is a script, 221 * the interpreter will launch but fail to open the script because its 222 * name ("/dev/fd/5/xxx....") is bigger than PATH_MAX. 223 * 224 * The failure code is usually 127 (POSIX: "If a command is not found, 225 * the exit status shall be 127."), but some systems give 126 (POSIX: 226 * "If the command name is found, but it is not an executable utility, 227 * the exit status shall be 126."), so allow either. 228 */ 229 if (is_script) 230 fail += check_execveat_invoked_rc(root_dfd, longpath + 1, 0, 231 127, 126); 232 else 233 fail += check_execveat(root_dfd, longpath + 1, 0); 234 235 return fail; 236 } 237 238 static int run_tests(void) 239 { 240 int fail = 0; 241 char *fullname = realpath("execveat", NULL); 242 char *fullname_script = realpath("script", NULL); 243 char *fullname_symlink = concat(fullname, ".symlink"); 244 int subdir_dfd = open_or_die("subdir", O_DIRECTORY|O_RDONLY); 245 int subdir_dfd_ephemeral = open_or_die("subdir.ephemeral", 246 O_DIRECTORY|O_RDONLY); 247 int dot_dfd = open_or_die(".", O_DIRECTORY|O_RDONLY); 248 int root_dfd = open_or_die("/", O_DIRECTORY|O_RDONLY); 249 int dot_dfd_path = open_or_die(".", O_DIRECTORY|O_RDONLY|O_PATH); 250 int dot_dfd_cloexec = open_or_die(".", O_DIRECTORY|O_RDONLY|O_CLOEXEC); 251 int fd = open_or_die("execveat", O_RDONLY); 252 int fd_path = open_or_die("execveat", O_RDONLY|O_PATH); 253 int fd_symlink = open_or_die("execveat.symlink", O_RDONLY); 254 int fd_denatured = open_or_die("execveat.denatured", O_RDONLY); 255 int fd_denatured_path = open_or_die("execveat.denatured", 256 O_RDONLY|O_PATH); 257 int fd_script = open_or_die("script", O_RDONLY); 258 int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY); 259 int fd_ephemeral_path = open_or_die("execveat.path.ephemeral", 260 O_RDONLY|O_PATH); 261 int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY); 262 int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC); 263 int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC); 264 265 /* Check if we have execveat at all, and bail early if not */ 266 errno = 0; 267 execveat_(-1, NULL, NULL, NULL, 0); 268 if (errno == ENOSYS) { 269 ksft_exit_skip( 270 "ENOSYS calling execveat - no kernel support?\n"); 271 } 272 273 /* Change file position to confirm it doesn't affect anything */ 274 lseek(fd, 10, SEEK_SET); 275 276 /* Normal executable file: */ 277 /* dfd + path */ 278 fail += check_execveat(subdir_dfd, "../execveat", 0); 279 fail += check_execveat(dot_dfd, "execveat", 0); 280 fail += check_execveat(dot_dfd_path, "execveat", 0); 281 /* absolute path */ 282 fail += check_execveat(AT_FDCWD, fullname, 0); 283 /* absolute path with nonsense dfd */ 284 fail += check_execveat(99, fullname, 0); 285 /* fd + no path */ 286 fail += check_execveat(fd, "", AT_EMPTY_PATH); 287 /* O_CLOEXEC fd + no path */ 288 fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH); 289 /* O_PATH fd */ 290 fail += check_execveat(fd_path, "", AT_EMPTY_PATH); 291 292 /* Mess with executable file that's already open: */ 293 /* fd + no path to a file that's been renamed */ 294 rename("execveat.ephemeral", "execveat.moved"); 295 fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH); 296 /* fd + no path to a file that's been deleted */ 297 unlink("execveat.moved"); /* remove the file now fd open */ 298 fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH); 299 300 /* Mess with executable file that's already open with O_PATH */ 301 /* fd + no path to a file that's been deleted */ 302 unlink("execveat.path.ephemeral"); 303 fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH); 304 305 /* Invalid argument failures */ 306 fail += check_execveat_fail(fd, "", 0, ENOENT); 307 fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT); 308 309 /* Symlink to executable file: */ 310 /* dfd + path */ 311 fail += check_execveat(dot_dfd, "execveat.symlink", 0); 312 fail += check_execveat(dot_dfd_path, "execveat.symlink", 0); 313 /* absolute path */ 314 fail += check_execveat(AT_FDCWD, fullname_symlink, 0); 315 /* fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */ 316 fail += check_execveat(fd_symlink, "", AT_EMPTY_PATH); 317 fail += check_execveat(fd_symlink, "", 318 AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW); 319 320 /* Symlink fails when AT_SYMLINK_NOFOLLOW set: */ 321 /* dfd + path */ 322 fail += check_execveat_fail(dot_dfd, "execveat.symlink", 323 AT_SYMLINK_NOFOLLOW, ELOOP); 324 fail += check_execveat_fail(dot_dfd_path, "execveat.symlink", 325 AT_SYMLINK_NOFOLLOW, ELOOP); 326 /* absolute path */ 327 fail += check_execveat_fail(AT_FDCWD, fullname_symlink, 328 AT_SYMLINK_NOFOLLOW, ELOOP); 329 330 /* Non-regular file failure */ 331 fail += check_execveat_fail(dot_dfd, "pipe", 0, EACCES); 332 unlink("pipe"); 333 334 /* Shell script wrapping executable file: */ 335 /* dfd + path */ 336 fail += check_execveat(subdir_dfd, "../script", 0); 337 fail += check_execveat(dot_dfd, "script", 0); 338 fail += check_execveat(dot_dfd_path, "script", 0); 339 /* absolute path */ 340 fail += check_execveat(AT_FDCWD, fullname_script, 0); 341 /* fd + no path */ 342 fail += check_execveat(fd_script, "", AT_EMPTY_PATH); 343 fail += check_execveat(fd_script, "", 344 AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW); 345 /* O_CLOEXEC fd fails for a script (as script file inaccessible) */ 346 fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH, 347 ENOENT); 348 fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT); 349 350 /* Mess with script file that's already open: */ 351 /* fd + no path to a file that's been renamed */ 352 rename("script.ephemeral", "script.moved"); 353 fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH); 354 /* fd + no path to a file that's been deleted */ 355 unlink("script.moved"); /* remove the file while fd open */ 356 fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH); 357 358 /* Rename a subdirectory in the path: */ 359 rename("subdir.ephemeral", "subdir.moved"); 360 fail += check_execveat(subdir_dfd_ephemeral, "../script", 0); 361 fail += check_execveat(subdir_dfd_ephemeral, "script", 0); 362 /* Remove the subdir and its contents */ 363 unlink("subdir.moved/script"); 364 unlink("subdir.moved"); 365 /* Shell loads via deleted subdir OK because name starts with .. */ 366 fail += check_execveat(subdir_dfd_ephemeral, "../script", 0); 367 fail += check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT); 368 369 /* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */ 370 fail += check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL); 371 /* Invalid path => ENOENT */ 372 fail += check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT); 373 fail += check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT); 374 fail += check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT); 375 /* Attempt to execute directory => EACCES */ 376 fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES); 377 /* Attempt to execute non-executable => EACCES */ 378 fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES); 379 fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES); 380 fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH, 381 EACCES); 382 /* Attempt to execute nonsense FD => EBADF */ 383 fail += check_execveat_fail(99, "", AT_EMPTY_PATH, EBADF); 384 fail += check_execveat_fail(99, "execveat", 0, EBADF); 385 /* Attempt to execute relative to non-directory => ENOTDIR */ 386 fail += check_execveat_fail(fd, "execveat", 0, ENOTDIR); 387 388 fail += check_execveat_pathmax(root_dfd, "execveat", 0); 389 fail += check_execveat_pathmax(root_dfd, "script", 1); 390 return fail; 391 } 392 393 static void prerequisites(void) 394 { 395 int fd; 396 const char *script = "#!/bin/sh\nexit $*\n"; 397 398 /* Create ephemeral copies of files */ 399 exe_cp("execveat", "execveat.ephemeral"); 400 exe_cp("execveat", "execveat.path.ephemeral"); 401 exe_cp("script", "script.ephemeral"); 402 mkdir("subdir.ephemeral", 0755); 403 404 fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755); 405 write(fd, script, strlen(script)); 406 close(fd); 407 408 mkfifo("pipe", 0755); 409 } 410 411 int main(int argc, char **argv) 412 { 413 int ii; 414 int rc; 415 const char *verbose = getenv("VERBOSE"); 416 417 if (argc >= 2) { 418 /* If we are invoked with an argument, don't run tests. */ 419 const char *in_test = getenv("IN_TEST"); 420 421 if (verbose) { 422 ksft_print_msg("invoked with:\n"); 423 for (ii = 0; ii < argc; ii++) 424 ksft_print_msg("\t[%d]='%s\n'", ii, argv[ii]); 425 } 426 427 /* Check expected environment transferred. */ 428 if (!in_test || strcmp(in_test, "yes") != 0) { 429 ksft_print_msg("no IN_TEST=yes in env\n"); 430 return 1; 431 } 432 433 /* Use the final argument as an exit code. */ 434 rc = atoi(argv[argc - 1]); 435 exit(rc); 436 } else { 437 ksft_print_header(); 438 ksft_set_plan(TESTS_EXPECTED); 439 prerequisites(); 440 if (verbose) 441 envp[1] = "VERBOSE=1"; 442 rc = run_tests(); 443 if (rc > 0) 444 printf("%d tests failed\n", rc); 445 ksft_finished(); 446 } 447 448 return rc; 449 } 450