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
execveat_(int fd,const char * path,char ** argv,char ** envp,int flags)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)
_check_execveat_fail(int fd,const char * path,int flags,int expected_errno,const char * errno_str)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
check_execveat_invoked_rc(int fd,const char * path,int flags,int expected_rc,int expected_rc2)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
check_execveat(int fd,const char * path,int flags)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
concat(const char * left,const char * right)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
open_or_die(const char * filename,int flags)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
exe_cp(const char * src,const char * dest)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
check_execveat_pathmax(int root_dfd,const char * src,int is_script)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
run_tests(void)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
prerequisites(void)374 static void prerequisites(void)
375 {
376 int fd;
377 const char *script = "#!/system/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
main(int argc,char ** argv)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 }
426