LXR linux/tools/testing/selftests/exec/execveat.c

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