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