| 1 | /* provide a replacement openat function
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| 2 | Copyright (C) 2004-2012 Free Software Foundation, Inc.
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| 3 |
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| 4 | This program is free software: you can redistribute it and/or modify
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| 5 | it under the terms of the GNU General Public License as published by
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| 6 | the Free Software Foundation; either version 3 of the License, or
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| 7 | (at your option) any later version.
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| 8 |
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| 9 | This program is distributed in the hope that it will be useful,
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| 10 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 12 | GNU General Public License for more details.
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| 13 |
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| 14 | You should have received a copy of the GNU General Public License
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| 15 | along with this program. If not, see <http://www.gnu.org/licenses/>. */
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| 16 |
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| 17 | /* written by Jim Meyering */
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| 18 |
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| 19 | /* If the user's config.h happens to include <fcntl.h>, let it include only
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| 20 | the system's <fcntl.h> here, so that orig_openat doesn't recurse to
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| 21 | rpl_openat. */
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| 22 | #define __need_system_fcntl_h
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| 23 | #include <config.h>
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| 24 |
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| 25 | /* Get the original definition of open. It might be defined as a macro. */
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| 26 | #include <fcntl.h>
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| 27 | #include <sys/types.h>
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| 28 | #undef __need_system_fcntl_h
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| 29 |
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| 30 | #if HAVE_OPENAT
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| 31 | static inline int
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| 32 | orig_openat (int fd, char const *filename, int flags, mode_t mode)
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| 33 | {
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| 34 | return openat (fd, filename, flags, mode);
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| 35 | }
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| 36 | #endif
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| 37 |
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| 38 | /* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates
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| 39 | this include because of the preliminary #include <fcntl.h> above. */
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| 40 | #include "fcntl.h"
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| 41 |
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| 42 | #include "openat.h"
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| 43 |
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| 44 | #include <stdarg.h>
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| 45 | #include <stdbool.h>
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| 46 | #include <stddef.h>
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| 47 | #include <string.h>
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| 48 | #include <sys/stat.h>
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| 49 | #include <errno.h>
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| 50 |
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| 51 | #if HAVE_OPENAT
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| 52 |
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| 53 | /* Like openat, but work around Solaris 9 bugs with trailing slash. */
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| 54 | int
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| 55 | rpl_openat (int dfd, char const *filename, int flags, ...)
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| 56 | {
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| 57 | mode_t mode;
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| 58 | int fd;
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| 59 |
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| 60 | mode = 0;
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| 61 | if (flags & O_CREAT)
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| 62 | {
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| 63 | va_list arg;
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| 64 | va_start (arg, flags);
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| 65 |
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| 66 | /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
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| 67 | creates crashing code when 'mode_t' is smaller than 'int'. */
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| 68 | mode = va_arg (arg, PROMOTED_MODE_T);
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| 69 |
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| 70 | va_end (arg);
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| 71 | }
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| 72 |
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| 73 | # if OPEN_TRAILING_SLASH_BUG
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| 74 | /* If the filename ends in a slash and one of O_CREAT, O_WRONLY, O_RDWR
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| 75 | is specified, then fail.
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| 76 | Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
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| 77 | says that
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| 78 | "A pathname that contains at least one non-slash character and that
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| 79 | ends with one or more trailing slashes shall be resolved as if a
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| 80 | single dot character ( '.' ) were appended to the pathname."
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| 81 | and
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| 82 | "The special filename dot shall refer to the directory specified by
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| 83 | its predecessor."
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| 84 | If the named file already exists as a directory, then
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| 85 | - if O_CREAT is specified, open() must fail because of the semantics
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| 86 | of O_CREAT,
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| 87 | - if O_WRONLY or O_RDWR is specified, open() must fail because POSIX
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| 88 | <http://www.opengroup.org/susv3/functions/open.html> says that it
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| 89 | fails with errno = EISDIR in this case.
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| 90 | If the named file does not exist or does not name a directory, then
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| 91 | - if O_CREAT is specified, open() must fail since open() cannot create
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| 92 | directories,
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| 93 | - if O_WRONLY or O_RDWR is specified, open() must fail because the
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| 94 | file does not contain a '.' directory. */
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| 95 | if (flags & (O_CREAT | O_WRONLY | O_RDWR))
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| 96 | {
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| 97 | size_t len = strlen (filename);
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| 98 | if (len > 0 && filename[len - 1] == '/')
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| 99 | {
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| 100 | errno = EISDIR;
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| 101 | return -1;
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| 102 | }
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| 103 | }
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| 104 | # endif
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| 105 |
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| 106 | fd = orig_openat (dfd, filename, flags, mode);
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| 107 |
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| 108 | # if OPEN_TRAILING_SLASH_BUG
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| 109 | /* If the filename ends in a slash and fd does not refer to a directory,
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| 110 | then fail.
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| 111 | Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
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| 112 | says that
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| 113 | "A pathname that contains at least one non-slash character and that
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| 114 | ends with one or more trailing slashes shall be resolved as if a
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| 115 | single dot character ( '.' ) were appended to the pathname."
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| 116 | and
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| 117 | "The special filename dot shall refer to the directory specified by
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| 118 | its predecessor."
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| 119 | If the named file without the slash is not a directory, open() must fail
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| 120 | with ENOTDIR. */
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| 121 | if (fd >= 0)
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| 122 | {
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| 123 | /* We know len is positive, since open did not fail with ENOENT. */
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| 124 | size_t len = strlen (filename);
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| 125 | if (filename[len - 1] == '/')
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| 126 | {
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| 127 | struct stat statbuf;
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| 128 |
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| 129 | if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
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| 130 | {
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| 131 | close (fd);
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| 132 | errno = ENOTDIR;
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| 133 | return -1;
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| 134 | }
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| 135 | }
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| 136 | }
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| 137 | # endif
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| 138 |
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| 139 | return fd;
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| 140 | }
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| 141 |
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| 142 | #else /* !HAVE_OPENAT */
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| 143 |
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| 144 | # include "dosname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
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| 145 | # include "openat-priv.h"
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| 146 | # include "save-cwd.h"
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| 147 |
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| 148 | /* Replacement for Solaris' openat function.
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| 149 | <http://www.google.com/search?q=openat+site:docs.sun.com>
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| 150 | First, try to simulate it via open ("/proc/self/fd/FD/FILE").
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| 151 | Failing that, simulate it by doing save_cwd/fchdir/open/restore_cwd.
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| 152 | If either the save_cwd or the restore_cwd fails (relatively unlikely),
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| 153 | then give a diagnostic and exit nonzero.
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| 154 | Otherwise, upon failure, set errno and return -1, as openat does.
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| 155 | Upon successful completion, return a file descriptor. */
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| 156 | int
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| 157 | openat (int fd, char const *file, int flags, ...)
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| 158 | {
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| 159 | mode_t mode = 0;
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| 160 |
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| 161 | if (flags & O_CREAT)
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| 162 | {
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| 163 | va_list arg;
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| 164 | va_start (arg, flags);
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| 165 |
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| 166 | /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
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| 167 | creates crashing code when 'mode_t' is smaller than 'int'. */
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| 168 | mode = va_arg (arg, PROMOTED_MODE_T);
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| 169 |
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| 170 | va_end (arg);
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| 171 | }
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| 172 |
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| 173 | return openat_permissive (fd, file, flags, mode, NULL);
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| 174 | }
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| 175 |
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| 176 | /* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is
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| 177 | nonnull, set *CWD_ERRNO to an errno value if unable to save
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| 178 | or restore the initial working directory. This is needed only
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| 179 | the first time remove.c's remove_dir opens a command-line
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| 180 | directory argument.
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| 181 |
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| 182 | If a previous attempt to restore the current working directory
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| 183 | failed, then we must not even try to access a '.'-relative name.
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| 184 | It is the caller's responsibility not to call this function
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| 185 | in that case. */
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| 186 |
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| 187 | int
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| 188 | openat_permissive (int fd, char const *file, int flags, mode_t mode,
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| 189 | int *cwd_errno)
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| 190 | {
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| 191 | struct saved_cwd saved_cwd;
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| 192 | int saved_errno;
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| 193 | int err;
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| 194 | bool save_ok;
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| 195 |
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| 196 | if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
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| 197 | return open (file, flags, mode);
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| 198 |
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| 199 | {
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| 200 | char buf[OPENAT_BUFFER_SIZE];
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| 201 | char *proc_file = openat_proc_name (buf, fd, file);
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| 202 | if (proc_file)
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| 203 | {
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| 204 | int open_result = open (proc_file, flags, mode);
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| 205 | int open_errno = errno;
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| 206 | if (proc_file != buf)
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| 207 | free (proc_file);
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| 208 | /* If the syscall succeeds, or if it fails with an unexpected
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| 209 | errno value, then return right away. Otherwise, fall through
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| 210 | and resort to using save_cwd/restore_cwd. */
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| 211 | if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
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| 212 | {
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| 213 | errno = open_errno;
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| 214 | return open_result;
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| 215 | }
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| 216 | }
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| 217 | }
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| 218 |
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| 219 | save_ok = (save_cwd (&saved_cwd) == 0);
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| 220 | if (! save_ok)
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| 221 | {
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| 222 | if (! cwd_errno)
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| 223 | openat_save_fail (errno);
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| 224 | *cwd_errno = errno;
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| 225 | }
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| 226 | if (0 <= fd && fd == saved_cwd.desc)
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| 227 | {
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| 228 | /* If saving the working directory collides with the user's
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| 229 | requested fd, then the user's fd must have been closed to
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| 230 | begin with. */
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| 231 | free_cwd (&saved_cwd);
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| 232 | errno = EBADF;
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| 233 | return -1;
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| 234 | }
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| 235 |
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| 236 | err = fchdir (fd);
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| 237 | saved_errno = errno;
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| 238 |
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| 239 | if (! err)
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| 240 | {
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| 241 | err = open (file, flags, mode);
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| 242 | saved_errno = errno;
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| 243 | if (save_ok && restore_cwd (&saved_cwd) != 0)
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| 244 | {
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| 245 | if (! cwd_errno)
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| 246 | {
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| 247 | /* Don't write a message to just-created fd 2. */
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| 248 | saved_errno = errno;
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| 249 | if (err == STDERR_FILENO)
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| 250 | close (err);
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| 251 | openat_restore_fail (saved_errno);
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| 252 | }
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| 253 | *cwd_errno = errno;
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| 254 | }
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| 255 | }
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| 256 |
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| 257 | free_cwd (&saved_cwd);
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| 258 | errno = saved_errno;
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| 259 | return err;
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| 260 | }
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| 261 |
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| 262 | /* Return true if our openat implementation must resort to
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| 263 | using save_cwd and restore_cwd. */
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| 264 | bool
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| 265 | openat_needs_fchdir (void)
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| 266 | {
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| 267 | bool needs_fchdir = true;
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| 268 | int fd = open ("/", O_SEARCH);
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| 269 |
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| 270 | if (0 <= fd)
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| 271 | {
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| 272 | char buf[OPENAT_BUFFER_SIZE];
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| 273 | char *proc_file = openat_proc_name (buf, fd, ".");
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| 274 | if (proc_file)
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| 275 | {
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| 276 | needs_fchdir = false;
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| 277 | if (proc_file != buf)
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| 278 | free (proc_file);
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| 279 | }
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| 280 | close (fd);
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| 281 | }
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| 282 |
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| 283 | return needs_fchdir;
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| 284 | }
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| 285 |
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| 286 | #endif /* !HAVE_OPENAT */
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