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#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
  24static char longpath[2 * PATH_MAX] = "";
  25static char *envp[] = { "IN_TEST=yes", NULL, NULL };
  26static char *argv[] = { "execveat", "99", NULL };
  27
  28static 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)
  41static 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
  65static 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
 112static int check_execveat(int fd, const char *path, int flags)
 113{
 114        return check_execveat_invoked_rc(fd, path, flags, 99, 99);
 115}
 116
 117static 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
 126static 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
 138static 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
 151static 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
 222static 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
 373static 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
 389int 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