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6ec2e0f5 | 1 | /* provide a replacement fdopendir function |
5e8754f9 | 2 | Copyright (C) 2004-2016 Free Software Foundation, Inc. |
6ec2e0f5 SDJ |
3 | |
4 | This program is free software: you can redistribute it and/or modify | |
5 | it under the terms of the GNU General Public License as published by | |
6 | the Free Software Foundation; either version 3 of the License, or | |
7 | (at your option) any later version. | |
8 | ||
9 | This program is distributed in the hope that it will be useful, | |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | GNU General Public License for more details. | |
13 | ||
14 | You should have received a copy of the GNU General Public License | |
5e8754f9 | 15 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
6ec2e0f5 SDJ |
16 | |
17 | /* written by Jim Meyering */ | |
18 | ||
19 | #include <config.h> | |
20 | ||
21 | #include <dirent.h> | |
22 | ||
23 | #include <stdlib.h> | |
24 | #include <unistd.h> | |
25 | ||
26 | #if !HAVE_FDOPENDIR | |
27 | ||
28 | # include "openat.h" | |
29 | # include "openat-priv.h" | |
30 | # include "save-cwd.h" | |
31 | ||
32 | # if GNULIB_DIRENT_SAFER | |
33 | # include "dirent--.h" | |
34 | # endif | |
35 | ||
36 | # ifndef REPLACE_FCHDIR | |
37 | # define REPLACE_FCHDIR 0 | |
38 | # endif | |
39 | ||
40 | static DIR *fdopendir_with_dup (int, int, struct saved_cwd const *); | |
41 | static DIR *fd_clone_opendir (int, struct saved_cwd const *); | |
42 | ||
43 | /* Replacement for POSIX fdopendir. | |
44 | ||
45 | First, try to simulate it via opendir ("/proc/self/fd/..."). Failing | |
46 | that, simulate it by using fchdir metadata, or by doing | |
47 | save_cwd/fchdir/opendir(".")/restore_cwd. | |
48 | If either the save_cwd or the restore_cwd fails (relatively unlikely), | |
49 | then give a diagnostic and exit nonzero. | |
50 | ||
51 | If successful, the resulting stream is based on FD in | |
52 | implementations where streams are based on file descriptors and in | |
53 | applications where no other thread or signal handler allocates or | |
54 | frees file descriptors. In other cases, consult dirfd on the result | |
55 | to find out whether FD is still being used. | |
56 | ||
57 | Otherwise, this function works just like POSIX fdopendir. | |
58 | ||
59 | W A R N I N G: | |
60 | ||
61 | Unlike other fd-related functions, this one places constraints on FD. | |
62 | If this function returns successfully, FD is under control of the | |
63 | dirent.h system, and the caller should not close or modify the state of | |
64 | FD other than by the dirent.h functions. */ | |
65 | # ifdef __KLIBC__ | |
66 | # include <InnoTekLIBC/backend.h> | |
67 | ||
68 | DIR * | |
69 | fdopendir (int fd) | |
70 | { | |
71 | char path[_MAX_PATH]; | |
72 | DIR *dirp; | |
73 | ||
74 | /* Get a path from fd */ | |
75 | if (__libc_Back_ioFHToPath (fd, path, sizeof (path))) | |
76 | return NULL; | |
77 | ||
78 | dirp = opendir (path); | |
79 | if (!dirp) | |
80 | return NULL; | |
81 | ||
82 | /* Unregister fd registered by opendir() */ | |
83 | _gl_unregister_dirp_fd (dirfd (dirp)); | |
84 | ||
85 | /* Register our fd */ | |
86 | if (_gl_register_dirp_fd (fd, dirp)) | |
87 | { | |
88 | int saved_errno = errno; | |
89 | ||
90 | closedir (dirp); | |
91 | ||
92 | errno = saved_errno; | |
93 | ||
94 | dirp = NULL; | |
95 | } | |
96 | ||
97 | return dirp; | |
98 | } | |
99 | # else | |
100 | DIR * | |
101 | fdopendir (int fd) | |
102 | { | |
103 | DIR *dir = fdopendir_with_dup (fd, -1, NULL); | |
104 | ||
105 | if (! REPLACE_FCHDIR && ! dir) | |
106 | { | |
107 | int saved_errno = errno; | |
108 | if (EXPECTED_ERRNO (saved_errno)) | |
109 | { | |
110 | struct saved_cwd cwd; | |
111 | if (save_cwd (&cwd) != 0) | |
112 | openat_save_fail (errno); | |
113 | dir = fdopendir_with_dup (fd, -1, &cwd); | |
114 | saved_errno = errno; | |
115 | free_cwd (&cwd); | |
116 | errno = saved_errno; | |
117 | } | |
118 | } | |
119 | ||
120 | return dir; | |
121 | } | |
122 | # endif | |
123 | ||
124 | /* Like fdopendir, except that if OLDER_DUPFD is not -1, it is known | |
125 | to be a dup of FD which is less than FD - 1 and which will be | |
126 | closed by the caller and not otherwise used by the caller. This | |
127 | function makes sure that FD is closed and all file descriptors less | |
128 | than FD are open, and then calls fd_clone_opendir on a dup of FD. | |
129 | That way, barring race conditions, fd_clone_opendir returns a | |
130 | stream whose file descriptor is FD. | |
131 | ||
132 | If REPLACE_FCHDIR or CWD is null, use opendir ("/proc/self/fd/...", | |
133 | falling back on fchdir metadata. Otherwise, CWD is a saved version | |
134 | of the working directory; use fchdir/opendir(".")/restore_cwd(CWD). */ | |
135 | static DIR * | |
136 | fdopendir_with_dup (int fd, int older_dupfd, struct saved_cwd const *cwd) | |
137 | { | |
138 | int dupfd = dup (fd); | |
139 | if (dupfd < 0 && errno == EMFILE) | |
140 | dupfd = older_dupfd; | |
141 | if (dupfd < 0) | |
142 | return NULL; | |
143 | else | |
144 | { | |
145 | DIR *dir; | |
146 | int saved_errno; | |
147 | if (dupfd < fd - 1 && dupfd != older_dupfd) | |
148 | { | |
149 | dir = fdopendir_with_dup (fd, dupfd, cwd); | |
150 | saved_errno = errno; | |
151 | } | |
152 | else | |
153 | { | |
154 | close (fd); | |
155 | dir = fd_clone_opendir (dupfd, cwd); | |
156 | saved_errno = errno; | |
157 | if (! dir) | |
158 | { | |
159 | int fd1 = dup (dupfd); | |
160 | if (fd1 != fd) | |
161 | openat_save_fail (fd1 < 0 ? errno : EBADF); | |
162 | } | |
163 | } | |
164 | ||
165 | if (dupfd != older_dupfd) | |
166 | close (dupfd); | |
167 | errno = saved_errno; | |
168 | return dir; | |
169 | } | |
170 | } | |
171 | ||
172 | /* Like fdopendir, except the result controls a clone of FD. It is | |
173 | the caller's responsibility both to close FD and (if the result is | |
174 | not null) to closedir the result. */ | |
175 | static DIR * | |
176 | fd_clone_opendir (int fd, struct saved_cwd const *cwd) | |
177 | { | |
178 | if (REPLACE_FCHDIR || ! cwd) | |
179 | { | |
180 | DIR *dir = NULL; | |
181 | int saved_errno = EOPNOTSUPP; | |
182 | char buf[OPENAT_BUFFER_SIZE]; | |
183 | char *proc_file = openat_proc_name (buf, fd, "."); | |
184 | if (proc_file) | |
185 | { | |
186 | dir = opendir (proc_file); | |
187 | saved_errno = errno; | |
188 | if (proc_file != buf) | |
189 | free (proc_file); | |
190 | } | |
191 | # if REPLACE_FCHDIR | |
192 | if (! dir && EXPECTED_ERRNO (saved_errno)) | |
193 | { | |
194 | char const *name = _gl_directory_name (fd); | |
195 | DIR *dp = name ? opendir (name) : NULL; | |
196 | ||
197 | /* The caller has done an elaborate dance to arrange for opendir to | |
198 | consume just the right file descriptor. If dirfd returns -1, | |
199 | though, we're on a system like mingw where opendir does not | |
200 | consume a file descriptor. Consume it via 'dup' instead. */ | |
201 | if (dp && dirfd (dp) < 0) | |
202 | dup (fd); | |
203 | ||
204 | return dp; | |
205 | } | |
206 | # endif | |
207 | errno = saved_errno; | |
208 | return dir; | |
209 | } | |
210 | else | |
211 | { | |
212 | if (fchdir (fd) != 0) | |
213 | return NULL; | |
214 | else | |
215 | { | |
216 | DIR *dir = opendir ("."); | |
217 | int saved_errno = errno; | |
218 | if (restore_cwd (cwd) != 0) | |
219 | openat_restore_fail (errno); | |
220 | errno = saved_errno; | |
221 | return dir; | |
222 | } | |
223 | } | |
224 | } | |
225 | ||
226 | #else /* HAVE_FDOPENDIR */ | |
227 | ||
228 | # include <errno.h> | |
229 | # include <sys/stat.h> | |
230 | ||
231 | # undef fdopendir | |
232 | ||
233 | /* Like fdopendir, but work around GNU/Hurd bug by validating FD. */ | |
234 | ||
235 | DIR * | |
236 | rpl_fdopendir (int fd) | |
237 | { | |
238 | struct stat st; | |
239 | if (fstat (fd, &st)) | |
240 | return NULL; | |
241 | if (!S_ISDIR (st.st_mode)) | |
242 | { | |
243 | errno = ENOTDIR; | |
244 | return NULL; | |
245 | } | |
246 | return fdopendir (fd); | |
247 | } | |
248 | ||
249 | #endif /* HAVE_FDOPENDIR */ |