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
execveat_(int fd,const char * path,char ** argv,char ** envp,int flags)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)
_check_execveat_fail(int fd,const char * path,int flags,int expected_errno,const char * errno_str)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
check_execveat_invoked_rc(int fd,const char * path,int flags,int expected_rc,int expected_rc2)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
check_execveat(int fd,const char * path,int flags)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
concat(const char * left,const char * right)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
open_or_die(const char * filename,int flags)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
exe_cp(const char * src,const char * dest)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
check_execveat_pathmax(int root_dfd,const char * src,int is_script)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
run_tests(void)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
prerequisites(void)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
main(int argc,char ** argv)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 }
433