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
execveat_(int fd,const char * path,char ** argv,char ** envp,int flags)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)
_check_execveat_fail(int fd,const char * path,int flags,int expected_errno,const char * errno_str)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
check_execveat_invoked_rc(int fd,const char * path,int flags,int expected_rc,int expected_rc2)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
check_execveat(int fd,const char * path,int flags)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
concat(const char * left,const char * right)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
open_or_die(const char * filename,int flags)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
exe_cp(const char * src,const char * dest)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
check_execveat_pathmax(int root_dfd,const char * src,int is_script)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
run_tests(void)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
prerequisites(void)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
main(int argc,char ** argv)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 }
425