| 1 | /* Define at-style functions like fstatat, unlinkat, fchownat, etc.
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| 2 | Copyright (C) 2006, 2009-2021 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 <https://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 | #include "filename.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
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| 20 |
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| 21 | #ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD
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| 22 | # include <errno.h>
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| 23 | # ifndef ENOTSUP
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| 24 | # define ENOTSUP EINVAL
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| 25 | # endif
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| 26 | #else
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| 27 | # include "openat.h"
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| 28 | # include "openat-priv.h"
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| 29 | # include "save-cwd.h"
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| 30 | #endif
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| 31 |
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| 32 | #ifdef AT_FUNC_USE_F1_COND
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| 33 | # define CALL_FUNC(F) \
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| 34 | (flag == AT_FUNC_USE_F1_COND \
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| 35 | ? AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS) \
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| 36 | : AT_FUNC_F2 (F AT_FUNC_POST_FILE_ARGS))
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| 37 | # define VALIDATE_FLAG(F) \
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| 38 | if (flag & ~AT_FUNC_USE_F1_COND) \
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| 39 | { \
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| 40 | errno = EINVAL; \
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| 41 | return FUNC_FAIL; \
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| 42 | }
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| 43 | #else
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| 44 | # define CALL_FUNC(F) (AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS))
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| 45 | # define VALIDATE_FLAG(F) /* empty */
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| 46 | #endif
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| 47 |
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| 48 | #ifdef AT_FUNC_RESULT
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| 49 | # define FUNC_RESULT AT_FUNC_RESULT
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| 50 | #else
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| 51 | # define FUNC_RESULT int
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| 52 | #endif
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| 53 |
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| 54 | #ifdef AT_FUNC_FAIL
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| 55 | # define FUNC_FAIL AT_FUNC_FAIL
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| 56 | #else
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| 57 | # define FUNC_FAIL -1
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| 58 | #endif
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| 59 |
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| 60 | /* Call AT_FUNC_F1 to operate on FILE, which is in the directory
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| 61 | open on descriptor FD. If AT_FUNC_USE_F1_COND is defined to a value,
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| 62 | AT_FUNC_POST_FILE_PARAM_DECLS must include a parameter named flag;
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| 63 | call AT_FUNC_F2 if FLAG is 0 or fail if FLAG contains more bits than
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| 64 | AT_FUNC_USE_F1_COND. Return int and fail with -1 unless AT_FUNC_RESULT
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| 65 | or AT_FUNC_FAIL are defined. If possible, do it without changing the
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| 66 | working directory. Otherwise, resort to using save_cwd/fchdir,
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| 67 | then AT_FUNC_F?/restore_cwd. If either the save_cwd or the restore_cwd
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| 68 | fails, then give a diagnostic and exit nonzero. */
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| 69 | FUNC_RESULT
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| 70 | AT_FUNC_NAME (int fd, char const *file AT_FUNC_POST_FILE_PARAM_DECLS)
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| 71 | {
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| 72 | VALIDATE_FLAG (flag);
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| 73 |
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| 74 | if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
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| 75 | return CALL_FUNC (file);
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| 76 |
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| 77 | #ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD
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| 78 | errno = ENOTSUP;
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| 79 | return FUNC_FAIL;
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| 80 | #else
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| 81 | {
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| 82 | /* Be careful to choose names unlikely to conflict with
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| 83 | AT_FUNC_POST_FILE_PARAM_DECLS. */
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| 84 | struct saved_cwd saved_cwd;
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| 85 | int saved_errno;
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| 86 | FUNC_RESULT err;
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| 87 |
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| 88 | {
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| 89 | char proc_buf[OPENAT_BUFFER_SIZE];
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| 90 | char *proc_file = openat_proc_name (proc_buf, fd, file);
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| 91 | if (proc_file)
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| 92 | {
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| 93 | FUNC_RESULT proc_result = CALL_FUNC (proc_file);
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| 94 | int proc_errno = errno;
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| 95 | if (proc_file != proc_buf)
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| 96 | free (proc_file);
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| 97 | /* If the syscall succeeds, or if it fails with an unexpected
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| 98 | errno value, then return right away. Otherwise, fall through
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| 99 | and resort to using save_cwd/restore_cwd. */
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| 100 | if (FUNC_FAIL != proc_result)
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| 101 | return proc_result;
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| 102 | if (! EXPECTED_ERRNO (proc_errno))
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| 103 | {
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| 104 | errno = proc_errno;
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| 105 | return proc_result;
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| 106 | }
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| 107 | }
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| 108 | }
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| 109 |
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| 110 | if (save_cwd (&saved_cwd) != 0)
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| 111 | openat_save_fail (errno);
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| 112 | if (0 <= fd && fd == saved_cwd.desc)
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| 113 | {
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| 114 | /* If saving the working directory collides with the user's
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| 115 | requested fd, then the user's fd must have been closed to
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| 116 | begin with. */
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| 117 | free_cwd (&saved_cwd);
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| 118 | errno = EBADF;
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| 119 | return FUNC_FAIL;
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| 120 | }
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| 121 |
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| 122 | if (fchdir (fd) != 0)
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| 123 | {
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| 124 | saved_errno = errno;
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| 125 | free_cwd (&saved_cwd);
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| 126 | errno = saved_errno;
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| 127 | return FUNC_FAIL;
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| 128 | }
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| 129 |
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| 130 | err = CALL_FUNC (file);
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| 131 | saved_errno = (err == FUNC_FAIL ? errno : 0);
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| 132 |
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| 133 | if (restore_cwd (&saved_cwd) != 0)
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| 134 | openat_restore_fail (errno);
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| 135 |
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| 136 | free_cwd (&saved_cwd);
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| 137 |
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| 138 | if (saved_errno)
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| 139 | errno = saved_errno;
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| 140 | return err;
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| 141 | }
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| 142 | #endif
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| 143 | }
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| 144 | #undef CALL_FUNC
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| 145 | #undef FUNC_RESULT
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| 146 | #undef FUNC_FAIL
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