111 lines
3.3 KiB
C
111 lines
3.3 KiB
C
/* Implement lchmod on platforms where it does not work correctly.
|
|
|
|
Copyright 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 Paul Eggert */
|
|
|
|
#include <config.h>
|
|
|
|
/* Specification. */
|
|
#include <sys/stat.h>
|
|
|
|
#include <errno.h>
|
|
#include <fcntl.h>
|
|
#include <stdio.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>
|
|
|
|
/* Work like chmod, except when FILE is a symbolic link.
|
|
In that case, on systems where permissions on symbolic links are unsupported
|
|
(such as Linux), set errno to EOPNOTSUPP and return -1. */
|
|
|
|
int
|
|
lchmod (char const *file, mode_t mode)
|
|
{
|
|
#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 = open (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. */
|
|
struct stat st;
|
|
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. */
|
|
|
|
#elif HAVE_LSTAT
|
|
struct stat st;
|
|
int lstat_result = lstat (file, &st);
|
|
if (lstat_result != 0)
|
|
return lstat_result;
|
|
if (S_ISLNK (st.st_mode))
|
|
{
|
|
errno = EOPNOTSUPP;
|
|
return -1;
|
|
}
|
|
#endif
|
|
|
|
/* Fall back on chmod, despite a possible race. */
|
|
return chmod (file, mode);
|
|
}
|