lib/utimensat.c

   1 /* Set the access and modification time of a file relative to directory fd.
   2    Copyright (C) 2009-2025 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* written by Eric Blake */
  18
  19 #include <config.h>
  20
  21 /* Specification.  */
  22 #include <sys/stat.h>
  23
  24 #include <errno.h>
  25 #include <fcntl.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <sys/stat.h>
  29
  30 #include "stat-time.h"
  31 #include "timespec.h"
  32 #include "utimens.h"
  33
  34 #if HAVE_NEARLY_WORKING_UTIMENSAT
  35
  36 /* Use the original utimensat(), but correct the trailing slash handling.  */
  37 int
  38 rpl_utimensat (int fd, char const *file, struct timespec const times[2],
  39                int flag)
  40 # undef utimensat
  41 {
  42   size_t len = strlen (file);
  43   if (len && file[len - 1] == '/')
  44     {
  45       struct stat st;
  46       if (fstatat (fd, file, &st, flag & AT_SYMLINK_NOFOLLOW) < 0)
  47         return -1;
  48       if (!S_ISDIR (st.st_mode))
  49         {
  50           errno = ENOTDIR;
  51           return -1;
  52         }
  53     }
  54
  55   return utimensat (fd, file, times, flag);
  56 }
  57
  58 #else
  59
  60 # if HAVE_UTIMENSAT
  61
  62 /* If we have a native utimensat, but are compiling this file, then
  63    utimensat was defined to rpl_utimensat by our replacement
  64    sys/stat.h.  We assume the native version might fail with ENOSYS,
  65    or succeed without properly affecting ctime (as is the case when
  66    using newer glibc but older Linux kernel).  In this scenario,
  67    rpl_utimensat checks whether the native version is usable, and
  68    local_utimensat provides the fallback manipulation.  */
  69
  70 static int local_utimensat (int, char const *, struct timespec const[2], int);
  71 #  define AT_FUNC_NAME local_utimensat
  72
  73 /* Like utimensat, but work around native bugs.  */
  74
  75 int
  76 rpl_utimensat (int fd, char const *file, struct timespec const times[2],
  77                int flag)
  78 #  undef utimensat
  79 {
  80 #  if defined __linux__ || defined __sun || defined __NetBSD__
  81   struct timespec ts[2];
  82 #  endif
  83
  84   /* See comments in utimens.c for details.  */
  85   static int utimensat_works_really; /* 0 = unknown, 1 = yes, -1 = no.  */
  86   if (0 <= utimensat_works_really)
  87     {
  88       int result;
  89 #  if defined __linux__ || defined __sun || defined __NetBSD__
  90       struct stat st;
  91       /* As recently as Linux kernel 2.6.32 (Dec 2009), several file
  92          systems (xfs, ntfs-3g) have bugs with a single UTIME_OMIT,
  93          but work if both times are either explicitly specified or
  94          UTIME_NOW.  Work around it with a preparatory [l]stat prior
  95          to calling utimensat; fortunately, there is not much timing
  96          impact due to the extra syscall even on file systems where
  97          UTIME_OMIT would have worked.
  98
  99          The same bug occurs in Solaris 11.1 (Apr 2013).
 100          The same bug occurs in NetBSD 10.0 (May 2024).
 101
 102          FIXME: Simplify this in 2024, when these file system bugs are
 103          no longer common on Gnulib target platforms.  */
 104       if (times && (times[0].tv_nsec == UTIME_OMIT
 105                     || times[1].tv_nsec == UTIME_OMIT))
 106         {
 107           if (fstatat (fd, file, &st, flag))
 108             return -1;
 109           if (times[0].tv_nsec == UTIME_OMIT && times[1].tv_nsec == UTIME_OMIT)
 110             return 0;
 111           if (times[0].tv_nsec == UTIME_OMIT)
 112             ts[0] = get_stat_atime (&st);
 113           else
 114             ts[0] = times[0];
 115           if (times[1].tv_nsec == UTIME_OMIT)
 116             ts[1] = get_stat_mtime (&st);
 117           else
 118             ts[1] = times[1];
 119           times = ts;
 120         }
 121 #   if defined __hppa__ || defined __NetBSD__
 122       /* Linux kernel 2.6.22.19 on hppa does not reject invalid tv_nsec
 123          values.
 124
 125          The same bug occurs in NetBSD 10.0 (May 2024).  */
 126       else if (times
 127                && ((times[0].tv_nsec != UTIME_NOW
 128                     && ! (0 <= times[0].tv_nsec
 129                           && times[0].tv_nsec < TIMESPEC_HZ))
 130                    || (times[1].tv_nsec != UTIME_NOW
 131                        && ! (0 <= times[1].tv_nsec
 132                              && times[1].tv_nsec < TIMESPEC_HZ))))
 133         {
 134           errno = EINVAL;
 135           return -1;
 136         }
 137 #   endif
 138 #  endif
 139 #  if defined __APPLE__ && defined __MACH__
 140       /* macOS 10.13 does not reject invalid tv_nsec values either.  */
 141       if (times
 142           && ((times[0].tv_nsec != UTIME_OMIT
 143                && times[0].tv_nsec != UTIME_NOW
 144                && ! (0 <= times[0].tv_nsec
 145                      && times[0].tv_nsec < TIMESPEC_HZ))
 146               || (times[1].tv_nsec != UTIME_OMIT
 147                   && times[1].tv_nsec != UTIME_NOW
 148                   && ! (0 <= times[1].tv_nsec
 149                         && times[1].tv_nsec < TIMESPEC_HZ))))
 150         {
 151           errno = EINVAL;
 152           return -1;
 153         }
 154       size_t len = strlen (file);
 155       if (len > 0 && file[len - 1] == '/')
 156         {
 157           struct stat statbuf;
 158           if (fstatat (fd, file, &statbuf, 0) < 0)
 159             return -1;
 160           if (!S_ISDIR (statbuf.st_mode))
 161             {
 162               errno = ENOTDIR;
 163               return -1;
 164             }
 165         }
 166 #  endif
 167       result = utimensat (fd, file, times, flag);
 168       /* Linux kernel 2.6.25 has a bug where it returns EINVAL for
 169          UTIME_NOW or UTIME_OMIT with non-zero tv_sec, which
 170          local_utimensat works around.  Meanwhile, EINVAL for a bad
 171          flag is indeterminate whether the native utimensat works, but
 172          local_utimensat will also reject it.  */
 173       if (result == -1 && errno == EINVAL && (flag & ~AT_SYMLINK_NOFOLLOW))
 174         return result;
 175       if (result == 0 || (errno != ENOSYS && errno != EINVAL))
 176         {
 177           utimensat_works_really = 1;
 178           return result;
 179         }
 180     }
 181   /* No point in trying openat/futimens, since on Linux, futimens is
 182      implemented with the same syscall as utimensat.  Only avoid the
 183      native utimensat due to an ENOSYS failure; an EINVAL error was
 184      data-dependent, and the next caller may pass valid data.  */
 185   if (0 <= utimensat_works_really && errno == ENOSYS)
 186     utimensat_works_really = -1;
 187   return local_utimensat (fd, file, times, flag);
 188 }
 189
 190 # else /* !HAVE_UTIMENSAT */
 191
 192 #  define AT_FUNC_NAME utimensat
 193
 194 # endif /* !HAVE_UTIMENSAT */
 195
 196 /* Set the access and modification timestamps of FILE to be
 197    TIMESPEC[0] and TIMESPEC[1], respectively; relative to directory
 198    FD.  If flag is AT_SYMLINK_NOFOLLOW, change the times of a symlink,
 199    or fail with ENOSYS if not possible.  If TIMESPEC is null, set the
 200    timestamps to the current time.  If possible, do it without
 201    changing the working directory.  Otherwise, resort to using
 202    save_cwd/fchdir, then utimens/restore_cwd.  If either the save_cwd
 203    or the restore_cwd fails, then give a diagnostic and exit nonzero.
 204    Return 0 on success, -1 (setting errno) on failure.  */
 205
 206 /* AT_FUNC_NAME is now utimensat or local_utimensat.  */
 207 # define AT_FUNC_F1 lutimens
 208 # define AT_FUNC_F2 utimens
 209 # define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
 210 # define AT_FUNC_POST_FILE_PARAM_DECLS , struct timespec const ts[2], int flag
 211 # define AT_FUNC_POST_FILE_ARGS        , ts
 212 # include "at-func.c"
 213 # undef AT_FUNC_NAME
 214 # undef AT_FUNC_F1
 215 # undef AT_FUNC_F2
 216 # undef AT_FUNC_USE_F1_COND
 217 # undef AT_FUNC_POST_FILE_PARAM_DECLS
 218 # undef AT_FUNC_POST_FILE_ARGS
 219
 220 #endif /* !HAVE_NEARLY_WORKING_UTIMENSAT */