| /* Change the protections of file relative to an open directory. |
| Copyright (C) 2006, 2009-2020 Free Software Foundation, Inc. |
| |
| This program is free software: you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
| |
| /* written by Jim Meyering and Paul Eggert */ |
| |
| /* If the user's config.h happens to include <sys/stat.h>, let it include only |
| the system's <sys/stat.h> here, so that orig_fchmodat doesn't recurse to |
| rpl_fchmodat. */ |
| #define __need_system_sys_stat_h |
| #include <config.h> |
| |
| /* Specification. */ |
| #include <sys/stat.h> |
| #undef __need_system_sys_stat_h |
| |
| #if HAVE_FCHMODAT |
| static int |
| orig_fchmodat (int dir, char const *file, mode_t mode, int flags) |
| { |
| return fchmodat (dir, file, mode, flags); |
| } |
| #endif |
| |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <unistd.h> |
| |
| #ifdef __osf__ |
| /* Write "sys/stat.h" here, not <sys/stat.h>, otherwise OSF/1 5.1 DTK cc |
| eliminates this include because of the preliminary #include <sys/stat.h> |
| above. */ |
| # include "sys/stat.h" |
| #else |
| # include <sys/stat.h> |
| #endif |
| |
| #include <intprops.h> |
| |
| /* Invoke chmod or lchmod on FILE, using mode MODE, in the directory |
| open on descriptor FD. If possible, do it without changing the |
| working directory. Otherwise, resort to using save_cwd/fchdir, |
| then (chmod|lchmod)/restore_cwd. If either the save_cwd or the |
| restore_cwd fails, then give a diagnostic and exit nonzero. |
| Note that an attempt to use a FLAG value of AT_SYMLINK_NOFOLLOW |
| on a system without lchmod support causes this function to fail. */ |
| |
| #if HAVE_FCHMODAT |
| int |
| fchmodat (int dir, char const *file, mode_t mode, int flags) |
| { |
| # if NEED_FCHMODAT_NONSYMLINK_FIX |
| if (flags == AT_SYMLINK_NOFOLLOW) |
| { |
| struct stat st; |
| |
| # if defined O_PATH && defined AT_EMPTY_PATH |
| /* Open a file descriptor with O_NOFOLLOW, to make sure we don't |
| follow symbolic links, if /proc is mounted. O_PATH is used to |
| avoid a failure if the file is not readable. |
| Cf. <https://sourceware.org/bugzilla/show_bug.cgi?id=14578> */ |
| int fd = openat (dir, file, O_PATH | O_NOFOLLOW | O_CLOEXEC); |
| if (fd < 0) |
| return fd; |
| |
| /* Up to Linux 5.3 at least, when FILE refers to a symbolic link, the |
| chmod call below will change the permissions of the symbolic link |
| - which is undesired - and on many file systems (ext4, btrfs, jfs, |
| xfs, ..., but not reiserfs) fail with error EOPNOTSUPP - which is |
| misleading. Therefore test for a symbolic link explicitly. |
| Use fstatat because fstat does not work on O_PATH descriptors |
| before Linux 3.6. */ |
| if (fstatat (fd, "", &st, AT_EMPTY_PATH) != 0) |
| { |
| int stat_errno = errno; |
| close (fd); |
| errno = stat_errno; |
| return -1; |
| } |
| if (S_ISLNK (st.st_mode)) |
| { |
| close (fd); |
| errno = EOPNOTSUPP; |
| return -1; |
| } |
| |
| # if defined __linux__ || defined __ANDROID__ |
| static char const fmt[] = "/proc/self/fd/%d"; |
| char buf[sizeof fmt - sizeof "%d" + INT_BUFSIZE_BOUND (int)]; |
| sprintf (buf, fmt, fd); |
| int chmod_result = chmod (buf, mode); |
| int chmod_errno = errno; |
| close (fd); |
| if (chmod_result == 0) |
| return chmod_result; |
| if (chmod_errno != ENOENT) |
| { |
| errno = chmod_errno; |
| return chmod_result; |
| } |
| # endif |
| /* /proc is not mounted or would not work as in GNU/Linux. */ |
| |
| # else |
| int fstatat_result = fstatat (dir, file, &st, AT_SYMLINK_NOFOLLOW); |
| if (fstatat_result != 0) |
| return fstatat_result; |
| if (S_ISLNK (st.st_mode)) |
| { |
| errno = EOPNOTSUPP; |
| return -1; |
| } |
| # endif |
| |
| /* Fall back on orig_fchmodat with no flags, despite a possible race. */ |
| flags = 0; |
| } |
| # endif |
| |
| return orig_fchmodat (dir, file, mode, flags); |
| } |
| #else |
| # define AT_FUNC_NAME fchmodat |
| # define AT_FUNC_F1 lchmod |
| # define AT_FUNC_F2 chmod |
| # define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW |
| # define AT_FUNC_POST_FILE_PARAM_DECLS , mode_t mode, int flag |
| # define AT_FUNC_POST_FILE_ARGS , mode |
| # include "at-func.c" |
| #endif |