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