src/basic/chattr-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright 2010 Lennart Poettering
   4 ***/
   5
   6 #include <errno.h>
   7 #include <fcntl.h>
   8 #include <sys/ioctl.h>
   9 #include <sys/stat.h>
  10 #include <linux/fs.h>
  11
  12 #include "chattr-util.h"
  13 #include "fd-util.h"
  14 #include "macro.h"
  15
  16 int chattr_fd(int fd, unsigned value, unsigned mask) {
  17         unsigned old_attr, new_attr;
  18         struct stat st;
  19
  20         assert(fd >= 0);
  21
  22         if (fstat(fd, &st) < 0)
  23                 return -errno;
  24
  25         /* Explicitly check whether this is a regular file or
  26          * directory. If it is anything else (such as a device node or
  27          * fifo), then the ioctl will not hit the file systems but
  28          * possibly drivers, where the ioctl might have different
  29          * effects. Notably, DRM is using the same ioctl() number. */
  30
  31         if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode))
  32                 return -ENOTTY;
  33
  34         if (mask == 0)
  35                 return 0;
  36
  37         if (ioctl(fd, FS_IOC_GETFLAGS, &old_attr) < 0)
  38                 return -errno;
  39
  40         new_attr = (old_attr & ~mask) | (value & mask);
  41         if (new_attr == old_attr)
  42                 return 0;
  43
  44         if (ioctl(fd, FS_IOC_SETFLAGS, &new_attr) < 0)
  45                 return -errno;
  46
  47         return 1;
  48 }
  49
  50 int chattr_path(const char *p, unsigned value, unsigned mask) {
  51         _cleanup_close_ int fd = -1;
  52
  53         assert(p);
  54
  55         if (mask == 0)
  56                 return 0;
  57
  58         fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
  59         if (fd < 0)
  60                 return -errno;
  61
  62         return chattr_fd(fd, value, mask);
  63 }
  64
  65 int read_attr_fd(int fd, unsigned *ret) {
  66         struct stat st;
  67
  68         assert(fd >= 0);
  69
  70         if (fstat(fd, &st) < 0)
  71                 return -errno;
  72
  73         if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode))
  74                 return -ENOTTY;
  75
  76         if (ioctl(fd, FS_IOC_GETFLAGS, ret) < 0)
  77                 return -errno;
  78
  79         return 0;
  80 }
  81
  82 int read_attr_path(const char *p, unsigned *ret) {
  83         _cleanup_close_ int fd = -1;
  84
  85         assert(p);
  86         assert(ret);
  87
  88         fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
  89         if (fd < 0)
  90                 return -errno;
  91
  92         return read_attr_fd(fd, ret);
  93 }