src/basic/chattr-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2010 Lennart Poettering
   6
   7   systemd is free software; you can redistribute it and/or modify it
   8   under the terms of the GNU Lesser General Public License as published by
   9   the Free Software Foundation; either version 2.1 of the License, or
  10   (at your option) any later version.
  11
  12   systemd is distributed in the hope that it will be useful, but
  13   WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15   Lesser General Public License for more details.
  16
  17   You should have received a copy of the GNU Lesser General Public License
  18   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  19 ***/
  20
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <sys/ioctl.h>
  24 #include <sys/stat.h>
  25 #include <linux/fs.h>
  26
  27 #include "chattr-util.h"
  28 #include "fd-util.h"
  29 #include "macro.h"
  30
  31 int chattr_fd(int fd, unsigned value, unsigned mask) {
  32         unsigned old_attr, new_attr;
  33         struct stat st;
  34
  35         assert(fd >= 0);
  36
  37         if (fstat(fd, &st) < 0)
  38                 return -errno;
  39
  40         /* Explicitly check whether this is a regular file or
  41          * directory. If it is anything else (such as a device node or
  42          * fifo), then the ioctl will not hit the file systems but
  43          * possibly drivers, where the ioctl might have different
  44          * effects. Notably, DRM is using the same ioctl() number. */
  45
  46         if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode))
  47                 return -ENOTTY;
  48
  49         if (mask == 0)
  50                 return 0;
  51
  52         if (ioctl(fd, FS_IOC_GETFLAGS, &old_attr) < 0)
  53                 return -errno;
  54
  55         new_attr = (old_attr & ~mask) | (value & mask);
  56         if (new_attr == old_attr)
  57                 return 0;
  58
  59         if (ioctl(fd, FS_IOC_SETFLAGS, &new_attr) < 0)
  60                 return -errno;
  61
  62         return 1;
  63 }
  64
  65 int chattr_path(const char *p, unsigned value, unsigned mask) {
  66         _cleanup_close_ int fd = -1;
  67
  68         assert(p);
  69
  70         if (mask == 0)
  71                 return 0;
  72
  73         fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
  74         if (fd < 0)
  75                 return -errno;
  76
  77         return chattr_fd(fd, value, mask);
  78 }
  79
  80 int read_attr_fd(int fd, unsigned *ret) {
  81         struct stat st;
  82
  83         assert(fd >= 0);
  84
  85         if (fstat(fd, &st) < 0)
  86                 return -errno;
  87
  88         if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode))
  89                 return -ENOTTY;
  90
  91         if (ioctl(fd, FS_IOC_GETFLAGS, ret) < 0)
  92                 return -errno;
  93
  94         return 0;
  95 }
  96
  97 int read_attr_path(const char *p, unsigned *ret) {
  98         _cleanup_close_ int fd = -1;
  99
 100         assert(p);
 101         assert(ret);
 102
 103         fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
 104         if (fd < 0)
 105                 return -errno;
 106
 107         return read_attr_fd(fd, ret);
 108 }