src/basic/chattr-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <sys/ioctl.h>
   6 #include <sys/stat.h>
   7 #include <linux/fs.h>
   8
   9 #include "chattr-util.h"
  10 #include "fd-util.h"
  11 #include "macro.h"
  12
  13 int chattr_fd(int fd, unsigned value, unsigned mask, unsigned *previous) {
  14         unsigned old_attr, new_attr;
  15         struct stat st;
  16
  17         assert(fd >= 0);
  18
  19         if (fstat(fd, &st) < 0)
  20                 return -errno;
  21
  22         /* Explicitly check whether this is a regular file or
  23          * directory. If it is anything else (such as a device node or
  24          * fifo), then the ioctl will not hit the file systems but
  25          * possibly drivers, where the ioctl might have different
  26          * effects. Notably, DRM is using the same ioctl() number. */
  27
  28         if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode))
  29                 return -ENOTTY;
  30
  31         if (mask == 0 && !previous)
  32                 return 0;
  33
  34         if (ioctl(fd, FS_IOC_GETFLAGS, &old_attr) < 0)
  35                 return -errno;
  36
  37         new_attr = (old_attr & ~mask) | (value & mask);
  38         if (new_attr == old_attr) {
  39                 if (previous)
  40                         *previous = old_attr;
  41                 return 0;
  42         }
  43
  44         if (ioctl(fd, FS_IOC_SETFLAGS, &new_attr) < 0)
  45                 return -errno;
  46
  47         if (previous)
  48                 *previous = old_attr;
  49
  50         return 1;
  51 }
  52
  53 int chattr_path(const char *p, unsigned value, unsigned mask, unsigned *previous) {
  54         _cleanup_close_ int fd = -1;
  55
  56         assert(p);
  57
  58         if (mask == 0)
  59                 return 0;
  60
  61         fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
  62         if (fd < 0)
  63                 return -errno;
  64
  65         return chattr_fd(fd, value, mask, previous);
  66 }
  67
  68 int read_attr_fd(int fd, unsigned *ret) {
  69         struct stat st;
  70
  71         assert(fd >= 0);
  72
  73         if (fstat(fd, &st) < 0)
  74                 return -errno;
  75
  76         if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode))
  77                 return -ENOTTY;
  78
  79         if (ioctl(fd, FS_IOC_GETFLAGS, ret) < 0)
  80                 return -errno;
  81
  82         return 0;
  83 }
  84
  85 int read_attr_path(const char *p, unsigned *ret) {
  86         _cleanup_close_ int fd = -1;
  87
  88         assert(p);
  89         assert(ret);
  90
  91         fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
  92         if (fd < 0)
  93                 return -errno;
  94
  95         return read_attr_fd(fd, ret);
  96 }