tools/testing/selftests/exec/execveat.c

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