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
  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 }