1 | /* Copyright (C) 1991-2020 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. |
3 | |
4 | The GNU C Library is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either |
7 | version 2.1 of the License, or (at your option) any later version. |
8 | |
9 | The GNU C Library 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 GNU |
12 | Lesser General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, see |
16 | <https://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <dirent.h> |
19 | #include <fcntl.h> |
20 | #include <errno.h> |
21 | #include <stdio.h> /* For BUFSIZ. */ |
22 | #include <sys/param.h> /* For MIN and MAX. */ |
23 | |
24 | #include <not-cancel.h> |
25 | |
26 | /* The st_blksize value of the directory is used as a hint for the |
27 | size of the buffer which receives struct dirent values from the |
28 | kernel. st_blksize is limited to MAX_DIR_BUFFER_SIZE, in case the |
29 | file system provides a bogus value. */ |
30 | #define MAX_DIR_BUFFER_SIZE 1048576U |
31 | |
32 | enum { |
33 | opendir_oflags = O_RDONLY|O_NDELAY|O_DIRECTORY|O_LARGEFILE|O_CLOEXEC |
34 | }; |
35 | |
36 | static bool |
37 | invalid_name (const char *name) |
38 | { |
39 | if (__glibc_unlikely (name[0] == '\0')) |
40 | { |
41 | /* POSIX.1-1990 says an empty name gets ENOENT; |
42 | but `open' might like it fine. */ |
43 | __set_errno (ENOENT); |
44 | return true; |
45 | } |
46 | return false; |
47 | } |
48 | |
49 | static DIR * |
50 | opendir_tail (int fd) |
51 | { |
52 | if (__glibc_unlikely (fd < 0)) |
53 | return NULL; |
54 | |
55 | /* Now make sure this really is a directory and nothing changed since the |
56 | `stat' call. The S_ISDIR check is superfluous if O_DIRECTORY works, |
57 | but it's cheap and we need the stat call for st_blksize anyway. */ |
58 | struct stat64 statbuf; |
59 | if (__glibc_unlikely (__fxstat64 (_STAT_VER, fd, &statbuf) < 0)) |
60 | goto lose; |
61 | if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode))) |
62 | { |
63 | __set_errno (ENOTDIR); |
64 | lose: |
65 | __close_nocancel_nostatus (fd); |
66 | return NULL; |
67 | } |
68 | |
69 | return __alloc_dir (fd, true, 0, &statbuf); |
70 | } |
71 | |
72 | |
73 | #if IS_IN (libc) |
74 | DIR * |
75 | __opendirat (int dfd, const char *name) |
76 | { |
77 | if (__glibc_unlikely (invalid_name (name))) |
78 | return NULL; |
79 | |
80 | return opendir_tail (__openat_nocancel (dfd, name, opendir_oflags)); |
81 | } |
82 | #endif |
83 | |
84 | |
85 | /* Open a directory stream on NAME. */ |
86 | DIR * |
87 | __opendir (const char *name) |
88 | { |
89 | if (__glibc_unlikely (invalid_name (name))) |
90 | return NULL; |
91 | |
92 | return opendir_tail (__open_nocancel (name, opendir_oflags)); |
93 | } |
94 | weak_alias (__opendir, opendir) |
95 | |
96 | DIR * |
97 | __alloc_dir (int fd, bool close_fd, int flags, const struct stat64 *statp) |
98 | { |
99 | /* We have to set the close-on-exit flag if the user provided the |
100 | file descriptor. */ |
101 | if (!close_fd |
102 | && __glibc_unlikely (__fcntl64_nocancel (fd, F_SETFD, FD_CLOEXEC) < 0)) |
103 | goto lose; |
104 | |
105 | const size_t default_allocation = (4 * BUFSIZ < sizeof (struct dirent64) |
106 | ? sizeof (struct dirent64) : 4 * BUFSIZ); |
107 | const size_t small_allocation = (BUFSIZ < sizeof (struct dirent64) |
108 | ? sizeof (struct dirent64) : BUFSIZ); |
109 | size_t allocation = default_allocation; |
110 | #ifdef _STATBUF_ST_BLKSIZE |
111 | /* Increase allocation if requested, but not if the value appears to |
112 | be bogus. */ |
113 | if (statp != NULL) |
114 | allocation = MIN (MAX ((size_t) statp->st_blksize, default_allocation), |
115 | MAX_DIR_BUFFER_SIZE); |
116 | #endif |
117 | |
118 | DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation); |
119 | if (dirp == NULL) |
120 | { |
121 | allocation = small_allocation; |
122 | dirp = (DIR *) malloc (sizeof (DIR) + allocation); |
123 | |
124 | if (dirp == NULL) |
125 | lose: |
126 | { |
127 | if (close_fd) |
128 | { |
129 | int save_errno = errno; |
130 | __close_nocancel_nostatus (fd); |
131 | __set_errno (save_errno); |
132 | } |
133 | return NULL; |
134 | } |
135 | } |
136 | |
137 | dirp->fd = fd; |
138 | #if IS_IN (libc) |
139 | __libc_lock_init (dirp->lock); |
140 | #endif |
141 | dirp->allocation = allocation; |
142 | dirp->size = 0; |
143 | dirp->offset = 0; |
144 | dirp->filepos = 0; |
145 | dirp->errcode = 0; |
146 | |
147 | return dirp; |
148 | } |
149 | |