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("child execveat() failed, rc=%d errno=%d (%s)\n", 102 rc, errno, strerror(errno)); 103 exit(errno); 104 } 105 /* Parent: wait for & check child's exit status. */ 106 rc = waitpid(child, &status, 0); 107 if (rc != child) { 108 ksft_print_msg("waitpid(%d,...) returned %d\n", child, rc); 109 ksft_test_result_fail("%s\n", test_name); 110 return 1; 111 } 112 if (!WIFEXITED(status)) { 113 ksft_print_msg("child %d did not exit cleanly, status=%08x\n", 114 child, status); 115 ksft_test_result_fail("%s\n", test_name); 116 return 1; 117 } 118 if ((WEXITSTATUS(status) != expected_rc) && 119 (WEXITSTATUS(status) != expected_rc2)) { 120 ksft_print_msg("child %d exited with %d not %d nor %d\n", 121 child, WEXITSTATUS(status), expected_rc, 122 expected_rc2); 123 ksft_test_result_fail("%s\n", test_name); 124 return 1; 125 } 126 ksft_test_result_pass("%s\n", test_name); 127 return 0; 128 } 129 130 static int check_execveat(int fd, const char *path, int flags) 131 { 132 return check_execveat_invoked_rc(fd, path, flags, 99, 99); 133 } 134 135 static char *concat(const char *left, const char *right) 136 { 137 char *result = malloc(strlen(left) + strlen(right) + 1); 138 139 strcpy(result, left); 140 strcat(result, right); 141 return result; 142 } 143 144 static int open_or_die(const char *filename, int flags) 145 { 146 int fd = open(filename, flags); 147 148 if (fd < 0) 149 ksft_exit_fail_msg("Failed to open '%s'; " 150 "check prerequisites are available\n", filename); 151 return fd; 152 } 153 154 static void exe_cp(const char *src, const char *dest) 155 { 156 int in_fd = open_or_die(src, O_RDONLY); 157 int out_fd = open(dest, O_RDWR|O_CREAT|O_TRUNC, 0755); 158 struct stat info; 159 160 fstat(in_fd, &info); 161 sendfile(out_fd, in_fd, NULL, info.st_size); 162 close(in_fd); 163 close(out_fd); 164 } 165 166 #define XX_DIR_LEN 200 167 static int check_execveat_pathmax(int root_dfd, const char *src, int is_script) 168 { 169 int fail = 0; 170 int ii, count, len; 171 char longname[XX_DIR_LEN + 1]; 172 int fd; 173 174 if (*longpath == '\0') { 175 /* Create a filename close to PATH_MAX in length */ 176 char *cwd = getcwd(NULL, 0); 177 178 if (!cwd) { 179 ksft_perror("Failed to getcwd()"); 180 return 2; 181 } 182 strcpy(longpath, cwd); 183 strcat(longpath, "/"); 184 memset(longname, 'x', XX_DIR_LEN - 1); 185 longname[XX_DIR_LEN - 1] = '/'; 186 longname[XX_DIR_LEN] = '\0'; 187 count = (PATH_MAX - 3 - strlen(cwd)) / XX_DIR_LEN; 188 for (ii = 0; ii < count; ii++) { 189 strcat(longpath, longname); 190 mkdir(longpath, 0755); 191 } 192 len = (PATH_MAX - 3 - strlen(cwd)) - (count * XX_DIR_LEN); 193 if (len <= 0) 194 len = 1; 195 memset(longname, 'y', len); 196 longname[len] = '\0'; 197 strcat(longpath, longname); 198 free(cwd); 199 } 200 exe_cp(src, longpath); 201 202 /* 203 * Execute as a pre-opened file descriptor, which works whether this is 204 * a script or not (because the interpreter sees a filename like 205 * "/dev/fd/20"). 206 */ 207 fd = open(longpath, O_RDONLY); 208 if (fd > 0) { 209 ksft_print_msg("Invoke copy of '%s' via filename of length %zu:\n", 210 src, strlen(longpath)); 211 fail += check_execveat(fd, "", AT_EMPTY_PATH); 212 } else { 213 ksft_print_msg("Failed to open length %zu filename, errno=%d (%s)\n", 214 strlen(longpath), errno, strerror(errno)); 215 fail++; 216 } 217 218 /* 219 * Execute as a long pathname relative to "/". If this is a script, 220 * the interpreter will launch but fail to open the script because its 221 * name ("/dev/fd/5/xxx....") is bigger than PATH_MAX. 222 * 223 * The failure code is usually 127 (POSIX: "If a command is not found, 224 * the exit status shall be 127."), but some systems give 126 (POSIX: 225 * "If the command name is found, but it is not an executable utility, 226 * the exit status shall be 126."), so allow either. 227 */ 228 if (is_script) { 229 ksft_print_msg("Invoke script via root_dfd and relative filename\n"); 230 fail += check_execveat_invoked_rc(root_dfd, longpath + 1, 0, 231 127, 126); 232 } else { 233 ksft_print_msg("Invoke exec via root_dfd and relative filename\n"); 234 fail += check_execveat(root_dfd, longpath + 1, 0); 235 } 236 237 return fail; 238 } 239 240 static int run_tests(void) 241 { 242 int fail = 0; 243 char *fullname = realpath("execveat", NULL); 244 char *fullname_script = realpath("script", NULL); 245 char *fullname_symlink = concat(fullname, ".symlink"); 246 int subdir_dfd = open_or_die("subdir", O_DIRECTORY|O_RDONLY); 247 int subdir_dfd_ephemeral = open_or_die("subdir.ephemeral", 248 O_DIRECTORY|O_RDONLY); 249 int dot_dfd = open_or_die(".", O_DIRECTORY|O_RDONLY); 250 int root_dfd = open_or_die("/", O_DIRECTORY|O_RDONLY); 251 int dot_dfd_path = open_or_die(".", O_DIRECTORY|O_RDONLY|O_PATH); 252 int dot_dfd_cloexec = open_or_die(".", O_DIRECTORY|O_RDONLY|O_CLOEXEC); 253 int fd = open_or_die("execveat", O_RDONLY); 254 int fd_path = open_or_die("execveat", O_RDONLY|O_PATH); 255 int fd_symlink = open_or_die("execveat.symlink", O_RDONLY); 256 int fd_denatured = open_or_die("execveat.denatured", O_RDONLY); 257 int fd_denatured_path = open_or_die("execveat.denatured", 258 O_RDONLY|O_PATH); 259 int fd_script = open_or_die("script", O_RDONLY); 260 int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY); 261 int fd_ephemeral_path = open_or_die("execveat.path.ephemeral", 262 O_RDONLY|O_PATH); 263 int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY); 264 int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC); 265 int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC); 266 267 /* Check if we have execveat at all, and bail early if not */ 268 errno = 0; 269 execveat_(-1, NULL, NULL, NULL, 0); 270 if (errno == ENOSYS) { 271 ksft_exit_skip( 272 "ENOSYS calling execveat - no kernel support?\n"); 273 } 274 275 /* Change file position to confirm it doesn't affect anything */ 276 lseek(fd, 10, SEEK_SET); 277 278 /* Normal executable file: */ 279 /* dfd + path */ 280 fail += check_execveat(subdir_dfd, "../execveat", 0); 281 fail += check_execveat(dot_dfd, "execveat", 0); 282 fail += check_execveat(dot_dfd_path, "execveat", 0); 283 /* absolute path */ 284 fail += check_execveat(AT_FDCWD, fullname, 0); 285 /* absolute path with nonsense dfd */ 286 fail += check_execveat(99, fullname, 0); 287 /* fd + no path */ 288 fail += check_execveat(fd, "", AT_EMPTY_PATH); 289 /* O_CLOEXEC fd + no path */ 290 fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH); 291 /* O_PATH fd */ 292 fail += check_execveat(fd_path, "", AT_EMPTY_PATH); 293 294 /* Mess with executable file that's already open: */ 295 /* fd + no path to a file that's been renamed */ 296 rename("execveat.ephemeral", "execveat.moved"); 297 fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH); 298 /* fd + no path to a file that's been deleted */ 299 unlink("execveat.moved"); /* remove the file now fd open */ 300 fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH); 301 302 /* Mess with executable file that's already open with O_PATH */ 303 /* fd + no path to a file that's been deleted */ 304 unlink("execveat.path.ephemeral"); 305 fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH); 306 307 /* Invalid argument failures */ 308 fail += check_execveat_fail(fd, "", 0, ENOENT); 309 fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT); 310 311 /* Symlink to executable file: */ 312 /* dfd + path */ 313 fail += check_execveat(dot_dfd, "execveat.symlink", 0); 314 fail += check_execveat(dot_dfd_path, "execveat.symlink", 0); 315 /* absolute path */ 316 fail += check_execveat(AT_FDCWD, fullname_symlink, 0); 317 /* fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */ 318 fail += check_execveat(fd_symlink, "", AT_EMPTY_PATH); 319 fail += check_execveat(fd_symlink, "", 320 AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW); 321 322 /* Symlink fails when AT_SYMLINK_NOFOLLOW set: */ 323 /* dfd + path */ 324 fail += check_execveat_fail(dot_dfd, "execveat.symlink", 325 AT_SYMLINK_NOFOLLOW, ELOOP); 326 fail += check_execveat_fail(dot_dfd_path, "execveat.symlink", 327 AT_SYMLINK_NOFOLLOW, ELOOP); 328 /* absolute path */ 329 fail += check_execveat_fail(AT_FDCWD, fullname_symlink, 330 AT_SYMLINK_NOFOLLOW, ELOOP); 331 332 /* Non-regular file failure */ 333 fail += check_execveat_fail(dot_dfd, "pipe", 0, EACCES); 334 unlink("pipe"); 335 336 /* Shell script wrapping executable file: */ 337 /* dfd + path */ 338 fail += check_execveat(subdir_dfd, "../script", 0); 339 fail += check_execveat(dot_dfd, "script", 0); 340 fail += check_execveat(dot_dfd_path, "script", 0); 341 /* absolute path */ 342 fail += check_execveat(AT_FDCWD, fullname_script, 0); 343 /* fd + no path */ 344 fail += check_execveat(fd_script, "", AT_EMPTY_PATH); 345 fail += check_execveat(fd_script, "", 346 AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW); 347 /* O_CLOEXEC fd fails for a script (as script file inaccessible) */ 348 fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH, 349 ENOENT); 350 fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT); 351 352 /* Mess with script file that's already open: */ 353 /* fd + no path to a file that's been renamed */ 354 rename("script.ephemeral", "script.moved"); 355 fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH); 356 /* fd + no path to a file that's been deleted */ 357 unlink("script.moved"); /* remove the file while fd open */ 358 fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH); 359 360 /* Rename a subdirectory in the path: */ 361 rename("subdir.ephemeral", "subdir.moved"); 362 fail += check_execveat(subdir_dfd_ephemeral, "../script", 0); 363 fail += check_execveat(subdir_dfd_ephemeral, "script", 0); 364 /* Remove the subdir and its contents */ 365 unlink("subdir.moved/script"); 366 unlink("subdir.moved"); 367 /* Shell loads via deleted subdir OK because name starts with .. */ 368 fail += check_execveat(subdir_dfd_ephemeral, "../script", 0); 369 fail += check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT); 370 371 /* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */ 372 fail += check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL); 373 /* Invalid path => ENOENT */ 374 fail += check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT); 375 fail += check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT); 376 fail += check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT); 377 /* Attempt to execute directory => EACCES */ 378 fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES); 379 /* Attempt to execute non-executable => EACCES */ 380 fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES); 381 fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES); 382 fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH, 383 EACCES); 384 /* Attempt to execute nonsense FD => EBADF */ 385 fail += check_execveat_fail(99, "", AT_EMPTY_PATH, EBADF); 386 fail += check_execveat_fail(99, "execveat", 0, EBADF); 387 /* Attempt to execute relative to non-directory => ENOTDIR */ 388 fail += check_execveat_fail(fd, "execveat", 0, ENOTDIR); 389 390 fail += check_execveat_pathmax(root_dfd, "execveat", 0); 391 fail += check_execveat_pathmax(root_dfd, "script", 1); 392 return fail; 393 } 394 395 static void prerequisites(void) 396 { 397 int fd; 398 const char *script = "#!/bin/bash\nexit $*\n"; 399 400 /* Create ephemeral copies of files */ 401 exe_cp("execveat", "execveat.ephemeral"); 402 exe_cp("execveat", "execveat.path.ephemeral"); 403 exe_cp("script", "script.ephemeral"); 404 mkdir("subdir.ephemeral", 0755); 405 406 fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755); 407 write(fd, script, strlen(script)); 408 close(fd); 409 410 mkfifo("pipe", 0755); 411 } 412 413 int main(int argc, char **argv) 414 { 415 int ii; 416 int rc; 417 const char *verbose = getenv("VERBOSE"); 418 419 if (argc >= 2) { 420 /* If we are invoked with an argument, don't run tests. */ 421 const char *in_test = getenv("IN_TEST"); 422 423 if (verbose) { 424 ksft_print_msg("invoked with:\n"); 425 for (ii = 0; ii < argc; ii++) 426 ksft_print_msg("\t[%d]='%s\n'", ii, argv[ii]); 427 } 428 429 /* Check expected environment transferred. */ 430 if (!in_test || strcmp(in_test, "yes") != 0) { 431 ksft_print_msg("no IN_TEST=yes in env\n"); 432 return 1; 433 } 434 435 /* Use the final argument as an exit code. */ 436 rc = atoi(argv[argc - 1]); 437 exit(rc); 438 } else { 439 ksft_print_header(); 440 ksft_set_plan(TESTS_EXPECTED); 441 prerequisites(); 442 if (verbose) 443 envp[1] = "VERBOSE=1"; 444 rc = run_tests(); 445 if (rc > 0) 446 printf("%d tests failed\n", rc); 447 ksft_finished(); 448 } 449 450 return rc; 451 } 452