1 /* Copyright (C) 1991-2021 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 enum {
27 opendir_oflags = O_RDONLY|O_NDELAY|O_DIRECTORY|O_LARGEFILE|O_CLOEXEC
28 };
29
30 static bool
invalid_name(const char * name)31 invalid_name (const char *name)
32 {
33 if (__glibc_unlikely (name[0] == '\0'))
34 {
35 /* POSIX.1-1990 says an empty name gets ENOENT;
36 but `open' might like it fine. */
37 __set_errno (ENOENT);
38 return true;
39 }
40 return false;
41 }
42
43 static DIR *
opendir_tail(int fd)44 opendir_tail (int fd)
45 {
46 if (__glibc_unlikely (fd < 0))
47 return NULL;
48
49 /* Now make sure this really is a directory and nothing changed since the
50 `stat' call. The S_ISDIR check is superfluous if O_DIRECTORY works,
51 but it's cheap and we need the stat call for st_blksize anyway. */
52 struct __stat64_t64 statbuf;
53 if (__glibc_unlikely (__fstat64_time64 (fd, &statbuf) < 0))
54 goto lose;
55 if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode)))
56 {
57 __set_errno (ENOTDIR);
58 lose:
59 __close_nocancel_nostatus (fd);
60 return NULL;
61 }
62
63 return __alloc_dir (fd, true, 0, &statbuf);
64 }
65
66
67 #if IS_IN (libc)
68 DIR *
__opendirat(int dfd,const char * name)69 __opendirat (int dfd, const char *name)
70 {
71 if (__glibc_unlikely (invalid_name (name)))
72 return NULL;
73
74 return opendir_tail (__openat_nocancel (dfd, name, opendir_oflags));
75 }
76 #endif
77
78
79 /* Open a directory stream on NAME. */
80 DIR *
__opendir(const char * name)81 __opendir (const char *name)
82 {
83 if (__glibc_unlikely (invalid_name (name)))
84 return NULL;
85
86 return opendir_tail (__open_nocancel (name, opendir_oflags));
87 }
weak_alias(__opendir,opendir)88 weak_alias (__opendir, opendir)
89
90 DIR *
91 __alloc_dir (int fd, bool close_fd, int flags,
92 const struct __stat64_t64 *statp)
93 {
94 /* We have to set the close-on-exit flag if the user provided the
95 file descriptor. */
96 if (!close_fd
97 && __glibc_unlikely (__fcntl64_nocancel (fd, F_SETFD, FD_CLOEXEC) < 0))
98 return NULL;
99
100 /* The st_blksize value of the directory is used as a hint for the
101 size of the buffer which receives struct dirent values from the
102 kernel. st_blksize is limited to max_buffer_size, in case the
103 file system provides a bogus value. */
104 enum { max_buffer_size = 1048576 };
105
106 enum { allocation_size = 32768 };
107 _Static_assert (allocation_size >= sizeof (struct dirent64),
108 "allocation_size < sizeof (struct dirent64)");
109
110 /* Increase allocation if requested, but not if the value appears to
111 be bogus. It will be between 32Kb and 1Mb. */
112 size_t allocation = MIN (MAX ((size_t) statp->st_blksize, (size_t)
113 allocation_size), (size_t) max_buffer_size);
114
115 DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation);
116 if (dirp == NULL)
117 {
118 if (close_fd)
119 __close_nocancel_nostatus (fd);
120 return NULL;
121 }
122
123 dirp->fd = fd;
124 #if IS_IN (libc)
125 __libc_lock_init (dirp->lock);
126 #endif
127 dirp->allocation = allocation;
128 dirp->size = 0;
129 dirp->offset = 0;
130 dirp->filepos = 0;
131 dirp->errcode = 0;
132
133 return dirp;
134 }
135