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
  26 static char longpath[2 * PATH_MAX] = "";
  27 static char *envp[] = { "IN_TEST=yes", NULL, NULL };
  28 static char *argv[] = { "execveat", "99", NULL };
  29
  30 static 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)
  43 static 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
  67 static 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
 114 static int check_execveat(int fd, const char *path, int flags)
 115 {
 116         return check_execveat_invoked_rc(fd, path, flags, 99, 99);
 117 }
 118
 119 static 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
 128 static 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
 140 static 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
 153 static 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
 224 static 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
 379 static 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
 397 int 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 }