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 "errno-util.h"
  11 #include "fd-util.h"
  12 #include "macro.h"
  13 #include "string-util.h"
  14
  15 int chattr_full(const char *path,
  16                 int fd,
  17                 unsigned value,
  18                 unsigned mask,
  19                 unsigned *ret_previous,
  20                 unsigned *ret_final,
  21                 ChattrApplyFlags flags) {
  22
  23         _cleanup_close_ int fd_will_close = -1;
  24         unsigned old_attr, new_attr;
  25         struct stat st;
  26
  27         assert(path || fd >= 0);
  28
  29         if (fd < 0) {
  30                 fd = fd_will_close = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
  31                 if (fd < 0)
  32                         return -errno;
  33         }
  34
  35         if (fstat(fd, &st) < 0)
  36                 return -errno;
  37
  38         /* Explicitly check whether this is a regular file or directory. If it is anything else (such
  39          * as a device node or fifo), then the ioctl will not hit the file systems but possibly
  40          * drivers, where the ioctl might have different effects. Notably, DRM is using the same
  41          * ioctl() number. */
  42
  43         if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode))
  44                 return -ENOTTY;
  45
  46         if (mask == 0 && !ret_previous && !ret_final)
  47                 return 0;
  48
  49         if (ioctl(fd, FS_IOC_GETFLAGS, &old_attr) < 0)
  50                 return -errno;
  51
  52         new_attr = (old_attr & ~mask) | (value & mask);
  53         if (new_attr == old_attr) {
  54                 if (ret_previous)
  55                         *ret_previous = old_attr;
  56                 if (ret_final)
  57                         *ret_final = old_attr;
  58                 return 0;
  59         }
  60
  61         if (ioctl(fd, FS_IOC_SETFLAGS, &new_attr) >= 0) {
  62                 if (ret_previous)
  63                         *ret_previous = old_attr;
  64                 if (ret_final)
  65                         *ret_final = new_attr;
  66                 return 1;
  67         }
  68
  69         if ((errno != EINVAL && !ERRNO_IS_NOT_SUPPORTED(errno)) ||
  70             !FLAGS_SET(flags, CHATTR_FALLBACK_BITWISE))
  71                 return -errno;
  72
  73         /* When -EINVAL is returned, we assume that incompatible attributes are simultaneously
  74          * specified. E.g., compress(c) and nocow(C) attributes cannot be set to files on btrfs.
  75          * As a fallback, let's try to set attributes one by one.
  76          *
  77          * Also, when we get EOPNOTSUPP (or a similar error code) we assume a flag might just not be
  78          * supported, and we can ignore it too */
  79
  80         unsigned current_attr = old_attr;
  81         for (unsigned i = 0; i < sizeof(unsigned) * 8; i++) {
  82                 unsigned new_one, mask_one = 1u << i;
  83
  84                 if (!FLAGS_SET(mask, mask_one))
  85                         continue;
  86
  87                 new_one = UPDATE_FLAG(current_attr, mask_one, FLAGS_SET(value, mask_one));
  88                 if (new_one == current_attr)
  89                         continue;
  90
  91                 if (ioctl(fd, FS_IOC_SETFLAGS, &new_one) < 0) {
  92                         if (errno != EINVAL && !ERRNO_IS_NOT_SUPPORTED(errno))
  93                                 return -errno;
  94
  95                         log_full_errno(FLAGS_SET(flags, CHATTR_WARN_UNSUPPORTED_FLAGS) ? LOG_WARNING : LOG_DEBUG,
  96                                        errno,
  97                                        "Unable to set file attribute 0x%x on %s, ignoring: %m", mask_one, strna(path));
  98                         continue;
  99                 }
 100
 101                 if (ioctl(fd, FS_IOC_GETFLAGS, &current_attr) < 0)
 102                         return -errno;
 103         }
 104
 105         if (ret_previous)
 106                 *ret_previous = old_attr;
 107         if (ret_final)
 108                 *ret_final = current_attr;
 109
 110         return current_attr == new_attr ? 1 : -ENOANO; /* -ENOANO indicates that some attributes cannot be set. */
 111 }
 112
 113 int read_attr_fd(int fd, unsigned *ret) {
 114         struct stat st;
 115
 116         assert(fd >= 0);
 117
 118         if (fstat(fd, &st) < 0)
 119                 return -errno;
 120
 121         if (!S_ISDIR(st.st_mode) && !S_ISREG(st.st_mode))
 122                 return -ENOTTY;
 123
 124         return RET_NERRNO(ioctl(fd, FS_IOC_GETFLAGS, ret));
 125 }
 126
 127 int read_attr_path(const char *p, unsigned *ret) {
 128         _cleanup_close_ int fd = -1;
 129
 130         assert(p);
 131         assert(ret);
 132
 133         fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
 134         if (fd < 0)
 135                 return -errno;
 136
 137         return read_attr_fd(fd, ret);
 138 }