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0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Copyright (c) 2014 Google, Inc.
0004  *
0005  * Selftests for execveat(2).
0006  */
0007 
0008 #ifndef _GNU_SOURCE
0009 #define _GNU_SOURCE  /* to get O_PATH, AT_EMPTY_PATH */
0010 #endif
0011 #include <sys/sendfile.h>
0012 #include <sys/stat.h>
0013 #include <sys/syscall.h>
0014 #include <sys/types.h>
0015 #include <sys/wait.h>
0016 #include <errno.h>
0017 #include <fcntl.h>
0018 #include <limits.h>
0019 #include <stdio.h>
0020 #include <stdlib.h>
0021 #include <string.h>
0022 #include <unistd.h>
0023 
0024 #include "../kselftest.h"
0025 
0026 static char longpath[2 * PATH_MAX] = "";
0027 static char *envp[] = { "IN_TEST=yes", NULL, NULL };
0028 static char *argv[] = { "execveat", "99", NULL };
0029 
0030 static int execveat_(int fd, const char *path, char **argv, char **envp,
0031              int flags)
0032 {
0033 #ifdef __NR_execveat
0034     return syscall(__NR_execveat, fd, path, argv, envp, flags);
0035 #else
0036     errno = ENOSYS;
0037     return -1;
0038 #endif
0039 }
0040 
0041 #define check_execveat_fail(fd, path, flags, errno) \
0042     _check_execveat_fail(fd, path, flags, errno, #errno)
0043 static int _check_execveat_fail(int fd, const char *path, int flags,
0044                 int expected_errno, const char *errno_str)
0045 {
0046     int rc;
0047 
0048     errno = 0;
0049     printf("Check failure of execveat(%d, '%s', %d) with %s... ",
0050         fd, path?:"(null)", flags, errno_str);
0051     rc = execveat_(fd, path, argv, envp, flags);
0052 
0053     if (rc > 0) {
0054         printf("[FAIL] (unexpected success from execveat(2))\n");
0055         return 1;
0056     }
0057     if (errno != expected_errno) {
0058         printf("[FAIL] (expected errno %d (%s) not %d (%s)\n",
0059             expected_errno, strerror(expected_errno),
0060             errno, strerror(errno));
0061         return 1;
0062     }
0063     printf("[OK]\n");
0064     return 0;
0065 }
0066 
0067 static int check_execveat_invoked_rc(int fd, const char *path, int flags,
0068                      int expected_rc, int expected_rc2)
0069 {
0070     int status;
0071     int rc;
0072     pid_t child;
0073     int pathlen = path ? strlen(path) : 0;
0074 
0075     if (pathlen > 40)
0076         printf("Check success of execveat(%d, '%.20s...%s', %d)... ",
0077             fd, path, (path + pathlen - 20), flags);
0078     else
0079         printf("Check success of execveat(%d, '%s', %d)... ",
0080             fd, path?:"(null)", flags);
0081     child = fork();
0082     if (child < 0) {
0083         printf("[FAIL] (fork() failed)\n");
0084         return 1;
0085     }
0086     if (child == 0) {
0087         /* Child: do execveat(). */
0088         rc = execveat_(fd, path, argv, envp, flags);
0089         printf("[FAIL]: execveat() failed, rc=%d errno=%d (%s)\n",
0090             rc, errno, strerror(errno));
0091         exit(1);  /* should not reach here */
0092     }
0093     /* Parent: wait for & check child's exit status. */
0094     rc = waitpid(child, &status, 0);
0095     if (rc != child) {
0096         printf("[FAIL] (waitpid(%d,...) returned %d)\n", child, rc);
0097         return 1;
0098     }
0099     if (!WIFEXITED(status)) {
0100         printf("[FAIL] (child %d did not exit cleanly, status=%08x)\n",
0101             child, status);
0102         return 1;
0103     }
0104     if ((WEXITSTATUS(status) != expected_rc) &&
0105         (WEXITSTATUS(status) != expected_rc2)) {
0106         printf("[FAIL] (child %d exited with %d not %d nor %d)\n",
0107             child, WEXITSTATUS(status), expected_rc, expected_rc2);
0108         return 1;
0109     }
0110     printf("[OK]\n");
0111     return 0;
0112 }
0113 
0114 static int check_execveat(int fd, const char *path, int flags)
0115 {
0116     return check_execveat_invoked_rc(fd, path, flags, 99, 99);
0117 }
0118 
0119 static char *concat(const char *left, const char *right)
0120 {
0121     char *result = malloc(strlen(left) + strlen(right) + 1);
0122 
0123     strcpy(result, left);
0124     strcat(result, right);
0125     return result;
0126 }
0127 
0128 static int open_or_die(const char *filename, int flags)
0129 {
0130     int fd = open(filename, flags);
0131 
0132     if (fd < 0) {
0133         printf("Failed to open '%s'; "
0134             "check prerequisites are available\n", filename);
0135         exit(1);
0136     }
0137     return fd;
0138 }
0139 
0140 static void exe_cp(const char *src, const char *dest)
0141 {
0142     int in_fd = open_or_die(src, O_RDONLY);
0143     int out_fd = open(dest, O_RDWR|O_CREAT|O_TRUNC, 0755);
0144     struct stat info;
0145 
0146     fstat(in_fd, &info);
0147     sendfile(out_fd, in_fd, NULL, info.st_size);
0148     close(in_fd);
0149     close(out_fd);
0150 }
0151 
0152 #define XX_DIR_LEN 200
0153 static int check_execveat_pathmax(int root_dfd, const char *src, int is_script)
0154 {
0155     int fail = 0;
0156     int ii, count, len;
0157     char longname[XX_DIR_LEN + 1];
0158     int fd;
0159 
0160     if (*longpath == '\0') {
0161         /* Create a filename close to PATH_MAX in length */
0162         char *cwd = getcwd(NULL, 0);
0163 
0164         if (!cwd) {
0165             printf("Failed to getcwd(), errno=%d (%s)\n",
0166                    errno, strerror(errno));
0167             return 2;
0168         }
0169         strcpy(longpath, cwd);
0170         strcat(longpath, "/");
0171         memset(longname, 'x', XX_DIR_LEN - 1);
0172         longname[XX_DIR_LEN - 1] = '/';
0173         longname[XX_DIR_LEN] = '\0';
0174         count = (PATH_MAX - 3 - strlen(cwd)) / XX_DIR_LEN;
0175         for (ii = 0; ii < count; ii++) {
0176             strcat(longpath, longname);
0177             mkdir(longpath, 0755);
0178         }
0179         len = (PATH_MAX - 3 - strlen(cwd)) - (count * XX_DIR_LEN);
0180         if (len <= 0)
0181             len = 1;
0182         memset(longname, 'y', len);
0183         longname[len] = '\0';
0184         strcat(longpath, longname);
0185         free(cwd);
0186     }
0187     exe_cp(src, longpath);
0188 
0189     /*
0190      * Execute as a pre-opened file descriptor, which works whether this is
0191      * a script or not (because the interpreter sees a filename like
0192      * "/dev/fd/20").
0193      */
0194     fd = open(longpath, O_RDONLY);
0195     if (fd > 0) {
0196         printf("Invoke copy of '%s' via filename of length %zu:\n",
0197             src, strlen(longpath));
0198         fail += check_execveat(fd, "", AT_EMPTY_PATH);
0199     } else {
0200         printf("Failed to open length %zu filename, errno=%d (%s)\n",
0201             strlen(longpath), errno, strerror(errno));
0202         fail++;
0203     }
0204 
0205     /*
0206      * Execute as a long pathname relative to "/".  If this is a script,
0207      * the interpreter will launch but fail to open the script because its
0208      * name ("/dev/fd/5/xxx....") is bigger than PATH_MAX.
0209      *
0210      * The failure code is usually 127 (POSIX: "If a command is not found,
0211      * the exit status shall be 127."), but some systems give 126 (POSIX:
0212      * "If the command name is found, but it is not an executable utility,
0213      * the exit status shall be 126."), so allow either.
0214      */
0215     if (is_script)
0216         fail += check_execveat_invoked_rc(root_dfd, longpath + 1, 0,
0217                           127, 126);
0218     else
0219         fail += check_execveat(root_dfd, longpath + 1, 0);
0220 
0221     return fail;
0222 }
0223 
0224 static int run_tests(void)
0225 {
0226     int fail = 0;
0227     char *fullname = realpath("execveat", NULL);
0228     char *fullname_script = realpath("script", NULL);
0229     char *fullname_symlink = concat(fullname, ".symlink");
0230     int subdir_dfd = open_or_die("subdir", O_DIRECTORY|O_RDONLY);
0231     int subdir_dfd_ephemeral = open_or_die("subdir.ephemeral",
0232                            O_DIRECTORY|O_RDONLY);
0233     int dot_dfd = open_or_die(".", O_DIRECTORY|O_RDONLY);
0234     int root_dfd = open_or_die("/", O_DIRECTORY|O_RDONLY);
0235     int dot_dfd_path = open_or_die(".", O_DIRECTORY|O_RDONLY|O_PATH);
0236     int dot_dfd_cloexec = open_or_die(".", O_DIRECTORY|O_RDONLY|O_CLOEXEC);
0237     int fd = open_or_die("execveat", O_RDONLY);
0238     int fd_path = open_or_die("execveat", O_RDONLY|O_PATH);
0239     int fd_symlink = open_or_die("execveat.symlink", O_RDONLY);
0240     int fd_denatured = open_or_die("execveat.denatured", O_RDONLY);
0241     int fd_denatured_path = open_or_die("execveat.denatured",
0242                         O_RDONLY|O_PATH);
0243     int fd_script = open_or_die("script", O_RDONLY);
0244     int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY);
0245     int fd_ephemeral_path = open_or_die("execveat.path.ephemeral",
0246                         O_RDONLY|O_PATH);
0247     int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY);
0248     int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC);
0249     int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC);
0250 
0251     /* Check if we have execveat at all, and bail early if not */
0252     errno = 0;
0253     execveat_(-1, NULL, NULL, NULL, 0);
0254     if (errno == ENOSYS) {
0255         ksft_exit_skip(
0256             "ENOSYS calling execveat - no kernel support?\n");
0257     }
0258 
0259     /* Change file position to confirm it doesn't affect anything */
0260     lseek(fd, 10, SEEK_SET);
0261 
0262     /* Normal executable file: */
0263     /*   dfd + path */
0264     fail += check_execveat(subdir_dfd, "../execveat", 0);
0265     fail += check_execveat(dot_dfd, "execveat", 0);
0266     fail += check_execveat(dot_dfd_path, "execveat", 0);
0267     /*   absolute path */
0268     fail += check_execveat(AT_FDCWD, fullname, 0);
0269     /*   absolute path with nonsense dfd */
0270     fail += check_execveat(99, fullname, 0);
0271     /*   fd + no path */
0272     fail += check_execveat(fd, "", AT_EMPTY_PATH);
0273     /*   O_CLOEXEC fd + no path */
0274     fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH);
0275     /*   O_PATH fd */
0276     fail += check_execveat(fd_path, "", AT_EMPTY_PATH);
0277 
0278     /* Mess with executable file that's already open: */
0279     /*   fd + no path to a file that's been renamed */
0280     rename("execveat.ephemeral", "execveat.moved");
0281     fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);
0282     /*   fd + no path to a file that's been deleted */
0283     unlink("execveat.moved"); /* remove the file now fd open */
0284     fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);
0285 
0286     /* Mess with executable file that's already open with O_PATH */
0287     /*   fd + no path to a file that's been deleted */
0288     unlink("execveat.path.ephemeral");
0289     fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH);
0290 
0291     /* Invalid argument failures */
0292     fail += check_execveat_fail(fd, "", 0, ENOENT);
0293     fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT);
0294 
0295     /* Symlink to executable file: */
0296     /*   dfd + path */
0297     fail += check_execveat(dot_dfd, "execveat.symlink", 0);
0298     fail += check_execveat(dot_dfd_path, "execveat.symlink", 0);
0299     /*   absolute path */
0300     fail += check_execveat(AT_FDCWD, fullname_symlink, 0);
0301     /*   fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */
0302     fail += check_execveat(fd_symlink, "", AT_EMPTY_PATH);
0303     fail += check_execveat(fd_symlink, "",
0304                    AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);
0305 
0306     /* Symlink fails when AT_SYMLINK_NOFOLLOW set: */
0307     /*   dfd + path */
0308     fail += check_execveat_fail(dot_dfd, "execveat.symlink",
0309                     AT_SYMLINK_NOFOLLOW, ELOOP);
0310     fail += check_execveat_fail(dot_dfd_path, "execveat.symlink",
0311                     AT_SYMLINK_NOFOLLOW, ELOOP);
0312     /*   absolute path */
0313     fail += check_execveat_fail(AT_FDCWD, fullname_symlink,
0314                     AT_SYMLINK_NOFOLLOW, ELOOP);
0315 
0316     /*  Non-regular file failure */
0317     fail += check_execveat_fail(dot_dfd, "pipe", 0, EACCES);
0318     unlink("pipe");
0319 
0320     /* Shell script wrapping executable file: */
0321     /*   dfd + path */
0322     fail += check_execveat(subdir_dfd, "../script", 0);
0323     fail += check_execveat(dot_dfd, "script", 0);
0324     fail += check_execveat(dot_dfd_path, "script", 0);
0325     /*   absolute path */
0326     fail += check_execveat(AT_FDCWD, fullname_script, 0);
0327     /*   fd + no path */
0328     fail += check_execveat(fd_script, "", AT_EMPTY_PATH);
0329     fail += check_execveat(fd_script, "",
0330                    AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);
0331     /*   O_CLOEXEC fd fails for a script (as script file inaccessible) */
0332     fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH,
0333                     ENOENT);
0334     fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT);
0335 
0336     /* Mess with script file that's already open: */
0337     /*   fd + no path to a file that's been renamed */
0338     rename("script.ephemeral", "script.moved");
0339     fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);
0340     /*   fd + no path to a file that's been deleted */
0341     unlink("script.moved"); /* remove the file while fd open */
0342     fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);
0343 
0344     /* Rename a subdirectory in the path: */
0345     rename("subdir.ephemeral", "subdir.moved");
0346     fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);
0347     fail += check_execveat(subdir_dfd_ephemeral, "script", 0);
0348     /* Remove the subdir and its contents */
0349     unlink("subdir.moved/script");
0350     unlink("subdir.moved");
0351     /* Shell loads via deleted subdir OK because name starts with .. */
0352     fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);
0353     fail += check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT);
0354 
0355     /* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */
0356     fail += check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL);
0357     /* Invalid path => ENOENT */
0358     fail += check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT);
0359     fail += check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT);
0360     fail += check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT);
0361     /* Attempt to execute directory => EACCES */
0362     fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES);
0363     /* Attempt to execute non-executable => EACCES */
0364     fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES);
0365     fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES);
0366     fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH,
0367                     EACCES);
0368     /* Attempt to execute nonsense FD => EBADF */
0369     fail += check_execveat_fail(99, "", AT_EMPTY_PATH, EBADF);
0370     fail += check_execveat_fail(99, "execveat", 0, EBADF);
0371     /* Attempt to execute relative to non-directory => ENOTDIR */
0372     fail += check_execveat_fail(fd, "execveat", 0, ENOTDIR);
0373 
0374     fail += check_execveat_pathmax(root_dfd, "execveat", 0);
0375     fail += check_execveat_pathmax(root_dfd, "script", 1);
0376     return fail;
0377 }
0378 
0379 static void prerequisites(void)
0380 {
0381     int fd;
0382     const char *script = "#!/bin/sh\nexit $*\n";
0383 
0384     /* Create ephemeral copies of files */
0385     exe_cp("execveat", "execveat.ephemeral");
0386     exe_cp("execveat", "execveat.path.ephemeral");
0387     exe_cp("script", "script.ephemeral");
0388     mkdir("subdir.ephemeral", 0755);
0389 
0390     fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755);
0391     write(fd, script, strlen(script));
0392     close(fd);
0393 
0394     mkfifo("pipe", 0755);
0395 }
0396 
0397 int main(int argc, char **argv)
0398 {
0399     int ii;
0400     int rc;
0401     const char *verbose = getenv("VERBOSE");
0402 
0403     if (argc >= 2) {
0404         /* If we are invoked with an argument, don't run tests. */
0405         const char *in_test = getenv("IN_TEST");
0406 
0407         if (verbose) {
0408             printf("  invoked with:");
0409             for (ii = 0; ii < argc; ii++)
0410                 printf(" [%d]='%s'", ii, argv[ii]);
0411             printf("\n");
0412         }
0413 
0414         /* Check expected environment transferred. */
0415         if (!in_test || strcmp(in_test, "yes") != 0) {
0416             printf("[FAIL] (no IN_TEST=yes in env)\n");
0417             return 1;
0418         }
0419 
0420         /* Use the final argument as an exit code. */
0421         rc = atoi(argv[argc - 1]);
0422         fflush(stdout);
0423     } else {
0424         prerequisites();
0425         if (verbose)
0426             envp[1] = "VERBOSE=1";
0427         rc = run_tests();
0428         if (rc > 0)
0429             printf("%d tests failed\n", rc);
0430     }
0431     return rc;
0432 }
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