[Bug-tar] [PATCH] tar: --dereference consistency

[Paul Eggert]

This closes another race condition, that occurs when overwriting a
symlink with a regular file.
* NEWS (--dereference consistency): New section.
* doc/tar.texi (Option Summary): Describe new --deference behavior.
(dereference): Likewise.  Remove discussion that I didn't follow,
even before --dereference was changed.
* src/common.h (deref_stat, set_file_atime): Adjust signatures.
* src/compare.c (diff_file, diff_multivol): Respect open_read_flags
instead of rolling our own flags.  This implements the new behavior
for --dereference.
(diff_file, diff_dumpdir): Likewise, for fstatat_flags.
* src/create.c: Adjust to set_file_atime signature change.
* src/extract.c (mark_after_links, file_newer_p, extract_dir):
Likewise.
* src/incremen.c (try_purge_directory): Likewise.
* src/misc.c (maybe_backup_file): Likewise.
* src/extract.c (file_newer_p): New arg STP.  All callers changed.
(maybe_recoverable): New arg REGULAR.  All callers changed.
Handle the case of overwriting a symlink with a regular file,
when --overwrite is specified but --dereference is not.
(open_output_file): Add O_CLOEXEC, O_NOCTTY, O_NONBLOCK for
consistency with file creation.  Add O_NOFOLLOW if
overwriting_old_files && ! dereference_option.
* src/incremen.c (update_parent_directory): Use fstat, not fstatat;
there's less to go wrong.
* src/misc.c (deref_stat): Remove DEREF arg.  All callers changed.
Instead, use fstatat_flags.
(set_file_atime): Remove ATFLAG arg.  All callers changed.
Instead, use fstatat_flags.
* src/names.c, src/update.c: Adjust to deref_stat signature change.
* src/tar.c (get_date_or_file): Use stat, not deref_stat, as this
is not a file to be archived.
* tests/Makefile.am (TESTSUITE_AT): Add extrac13.at.
* tests/extrac13.at: New file.
* tests/testsuite.at: Include it.
---
 NEWS               |   18 ++++++-
 doc/tar.texi       |   41 +++++++---------
 src/common.h       |    4 +-
 src/compare.c      |   24 ++-------
 src/create.c       |    4 +-
 src/extract.c      |  140 ++++++++++++++++++++++++++++++---------------------
 src/incremen.c     |    4 +-
 src/misc.c         |   18 +++---
 src/names.c        |    4 +-
 src/tar.c          |    2 +-
 src/update.c       |    3 +-
 tests/Makefile.am  |    1 +
 tests/extrac13.at  |   53 ++++++++++++++++++++
 tests/testsuite.at |    1 +
 14 files changed, 195 insertions(+), 122 deletions(-)
 create mode 100644 tests/extrac13.at

diff --git a/NEWS b/NEWS
index 58fd2ff..1484c55 100644
--- a/NEWS
+++ b/NEWS
@@ -1,4 +1,4 @@
-GNU tar NEWS - User visible changes. 2010-09-17
+GNU tar NEWS - User visible changes. 2010-09-23
 Please send GNU tar bug reports to <address@hidden>
 
 
@@ -33,6 +33,22 @@ supports this.  For example, recent versions of the Linux 
kernel
 support setting times on symlinks, and some BSD kernels also support
 symlink permissions.
 
+** --dereference consistency
+
+The --dereference (-h) option now applies to files that are copied
+into or out of archives, independently of other options.  For example,
+if F is a symbolic link and archive.tar contains a regular-file member
+also named F, "tar --overwrite -x -f archive.tar F" now overwrites F
+itself, rather than the file that F points to.  (To overwrite the file
+that F points to, add the --dereference (-h) option.)  Formerly,
+--dereference was intended to apply only when using the -c option, but
+the implementation was not consistent.
+
+Also, the --dereference option no longer affects accesses to other
+files, such as archives and time stamp files.  Symbolic links to these
+files are always followed.  Previously, the links were usually but not
+always followed.
+
 ** Spurious error diagnostics on broken pipe.
 
 When receiving SIGPIPE, tar would exit with error status and
diff --git a/doc/tar.texi b/doc/tar.texi
index 983e47a..23a5e76 100644
--- a/doc/tar.texi
+++ b/doc/tar.texi
@@ -2559,9 +2559,9 @@ directories until the end of extraction. @xref{Directory 
Modification Times and
 @item --dereference
 @itemx -h
 
-When creating a @command{tar} archive, @command{tar} will archive the
-file that a symbolic link points to, rather than archiving the
-symlink.  @xref{dereference}.
+When reading or writing a file to be archived, @command{tar} accesses
+the file that a symbolic link points to, rather than the symlink
+itself.  @xref{dereference}.
 
 @opsummary{directory}
 @item address@hidden
@@ -9319,30 +9319,25 @@ than System V's.
 Normally, when @command{tar} archives a symbolic link, it writes a
 block to the archive naming the target of the link.  In that way, the
 @command{tar} archive is a faithful record of the file system contents.
address@hidden (@option{-h}) is used with @option{--create} (@option{-c}), and 
causes
address@hidden to archive the files symbolic links point to, instead of
-the links themselves.  When this option is used, when @command{tar}
-encounters a symbolic link, it will archive the linked-to file,
-instead of simply recording the presence of a symbolic link.
-
-The name under which the file is stored in the file system is not
-recorded in the archive.  To record both the symbolic link name and
-the file name in the system, archive the file under both names.  If
-all links were recorded automatically by @command{tar}, an extracted file
-might be linked to a file name that no longer exists in the file
-system.
-
-If a linked-to file is encountered again by @command{tar} while creating
-the same archive, an entire second copy of it will be stored.  (This
address@hidden be considered a bug.)
+When @option{--dereference} (@option{-h}) is used with
address@hidden (@option{-c}), @command{tar} archives the files
+symbolic links point to, instead of
+the links themselves.
 
-So, for portable archives, do not archive symbolic links as such,
-and use @option{--dereference} (@option{-h}): many systems do not support
+When creating portable archives, use @option{--dereference}
+(@option{-h}): some systems do not support
 symbolic links, and moreover, your distribution might be unusable if
 it contains unresolved symbolic links.
 
-The @option{--dereference} option is not secure if an untrusted user
-can modify files during creation or extraction.  @xref{Security}.
+When reading from an archive, the @option{--dereference} (@option{-h})
+option causes @command{tar} to follow an already-existing symbolic
+link when @command{tar} writes or reads a file named in the archive.
+Ordinarily, @command{tar} does not follow such a link, though it may
+remove the link before writing a new file.  @xref{Dealing with Old
+Files}.
+
+The @option{--dereference} option is unsafe if an untrusted user can
+modify directories while @command{tar} is running.  @xref{Security}.
 
 @node hard links
 @subsection Hard Links
diff --git a/src/common.h b/src/common.h
index 12a4889..192cf9e 100644
--- a/src/common.h
+++ b/src/common.h
@@ -611,7 +611,7 @@ int remove_any_file (const char *file_name, enum 
remove_option option);
 bool maybe_backup_file (const char *file_name, bool this_is_the_archive);
 void undo_last_backup (void);
 
-int deref_stat (bool deref, char const *name, struct stat *buf);
+int deref_stat (char const *name, struct stat *buf);
 
 extern int chdir_current;
 extern int chdir_fd;
@@ -640,7 +640,7 @@ void xpipe (int fd[2]);
 
 void *page_aligned_alloc (void **ptr, size_t size);
 int set_file_atime (int fd, int parentfd, char const *file,
-                   struct timespec atime, int atflag);
+                   struct timespec atime);
 
 /* Module names.c.  */
 
diff --git a/src/compare.c b/src/compare.c
index 1ee9bcb..6b7e6d8 100644
--- a/src/compare.c
+++ b/src/compare.c
@@ -151,7 +151,7 @@ read_and_process (struct tar_stat_info *st, int 
(*processor) (size_t, char *))
 static int
 get_stat_data (char const *file_name, struct stat *stat_data)
 {
-  int status = deref_stat (dereference_option, file_name, stat_data);
+  int status = deref_stat (file_name, stat_data);
 
   if (status != 0)
     {
@@ -217,14 +217,7 @@ diff_file (void)
        }
       else
        {
-         int atime_flag =
-           (atime_preserve_option == system_atime_preserve
-            ? O_NOATIME
-            : 0);
-
-         diff_handle = openat (chdir_fd, file_name,
-                               (O_RDONLY | O_BINARY | O_CLOEXEC | O_NOCTTY
-                                | O_NONBLOCK | atime_flag));
+         diff_handle = openat (chdir_fd, file_name, open_read_flags);
 
          if (diff_handle < 0)
            {
@@ -244,8 +237,7 @@ diff_file (void)
              if (atime_preserve_option == replace_atime_preserve)
                {
                  struct timespec atime = get_stat_atime (&stat_data);
-                 if (set_file_atime (diff_handle, chdir_fd, file_name,
-                                     atime, 0)
+                 if (set_file_atime (diff_handle, chdir_fd, file_name, atime)
                      != 0)
                    utime_error (file_name);
                }
@@ -372,7 +364,7 @@ diff_dumpdir (void)
   dev_t dev = 0;
   struct stat stat_data;
 
-  if (deref_stat (true, current_stat_info.file_name, &stat_data))
+  if (deref_stat (current_stat_info.file_name, &stat_data) != 0)
     {
       if (errno == ENOENT)
        stat_warn (current_stat_info.file_name);
@@ -399,10 +391,6 @@ diff_multivol (void)
   struct stat stat_data;
   int fd, status;
   off_t offset;
-  int atime_flag =
-    (atime_preserve_option == system_atime_preserve
-     ? O_NOATIME
-     : 0);
 
   if (current_stat_info.had_trailing_slash)
     {
@@ -429,9 +417,7 @@ diff_multivol (void)
     }
 
 
-  fd = openat (chdir_fd, current_stat_info.file_name,
-              (O_RDONLY | O_BINARY | O_CLOEXEC | O_NOCTTY | O_NONBLOCK
-               | atime_flag));
+  fd = openat (chdir_fd, current_stat_info.file_name, open_read_flags);
 
   if (fd < 0)
     {
diff --git a/src/create.c b/src/create.c
index 26993c2..05af0d9 100644
--- a/src/create.c
+++ b/src/create.c
@@ -1795,9 +1795,7 @@ dump_file0 (struct tar_stat_info *st, char const *name, 
char const *p)
              set_exit_status (TAREXIT_DIFFERS);
            }
          else if (atime_preserve_option == replace_atime_preserve
-                  && (set_file_atime (fd, parentfd, name,
-                                      st->atime, fstatat_flags)
-                      != 0))
+                  && set_file_atime (fd, parentfd, name, st->atime) != 0)
            utime_error (p);
        }
 
diff --git a/src/extract.c b/src/extract.c
index 2730a03..0a1a032 100644
--- a/src/extract.c
+++ b/src/extract.c
@@ -375,7 +375,7 @@ mark_after_links (struct delayed_set_stat *head)
       struct stat st;
       h->after_links = 1;
 
-      if (fstatat (chdir_fd, h->file_name, &st, 0) != 0)
+      if (deref_stat (h->file_name, &st) != 0)
        stat_error (h->file_name);
       else
        {
@@ -548,27 +548,32 @@ make_directories (char *file_name)
   return did_something;                /* tell them to retry if we made one */
 }
 
+/* Return true if FILE_NAME (with status *STP, if STP) is not a
+   directory, and has a time stamp newer than (or equal to) that of
+   TAR_STAT.  */
 static bool
-file_newer_p (const char *file_name, struct tar_stat_info *tar_stat)
+file_newer_p (const char *file_name, struct stat const *stp,
+             struct tar_stat_info *tar_stat)
 {
   struct stat st;
 
-  if (fstatat (chdir_fd, file_name, &st, 0))
+  if (!stp)
     {
-      if (errno != ENOENT)
+      if (deref_stat (file_name, &st) != 0)
        {
-         stat_warn (file_name);
-         /* Be on the safe side: if the file does exist assume it is newer */
-         return true;
+         if (errno != ENOENT)
+           {
+             stat_warn (file_name);
+             /* Be safer: if the file exists, assume it is newer.  */
+             return true;
+           }
+         return false;
        }
-      return false;
-    }
-  if (!S_ISDIR (st.st_mode)
-      && tar_timespec_cmp (tar_stat->mtime, get_stat_mtime (&st)) <= 0)
-    {
-      return true;
+      stp = &st;
     }
-  return false;
+
+  return (! S_ISDIR (stp->st_mode)
+         && tar_timespec_cmp (tar_stat->mtime, get_stat_mtime (stp)) <= 0);
 }
 
 #define RECOVER_NO 0
@@ -580,18 +585,39 @@ file_newer_p (const char *file_name, struct tar_stat_info 
*tar_stat)
    Return RECOVER_OK if we somewhat increased our chances at a successful
    extraction, RECOVER_NO if there are no chances, and RECOVER_SKIP if the
    caller should skip extraction of that member.  The value of errno is
-   properly restored on returning RECOVER_NO.  */
+   properly restored on returning RECOVER_NO.
+
+   If REGULAR, the caller was trying to extract onto a regular file.
+
+   Set *INTERDIR_MADE if an intermediate directory is made as part of
+   the recovery process.  */
 
 static int
-maybe_recoverable (char *file_name, bool *interdir_made)
+maybe_recoverable (char *file_name, bool regular, bool *interdir_made)
 {
   int e = errno;
+  struct stat st;
+  struct stat const *stp = 0;
 
   if (*interdir_made)
     return RECOVER_NO;
 
-  switch (errno)
+  switch (e)
     {
+    case ELOOP:
+      if (! regular
+         || old_files_option != OVERWRITE_OLD_FILES || dereference_option)
+       break;
+      if (strchr (file_name, '/'))
+       {
+         if (deref_stat (file_name, &st) != 0)
+           break;
+         stp = &st;
+       }
+
+      /* The caller tried to open a symbolic link with O_NOFOLLOW.
+        Fall through, treating it as an already-existing file.  */
+
     case EEXIST:
       /* Remove an old file, if the options allow this.  */
 
@@ -601,21 +627,16 @@ maybe_recoverable (char *file_name, bool *interdir_made)
          return RECOVER_SKIP;
 
        case KEEP_NEWER_FILES:
-         if (file_newer_p (file_name, &current_stat_info))
-           {
-             errno = e;
-             return RECOVER_NO;
-           }
+         if (file_newer_p (file_name, stp, &current_stat_info))
+           break;
          /* FALL THROUGH */
 
        case DEFAULT_OLD_FILES:
        case NO_OVERWRITE_DIR_OLD_FILES:
        case OVERWRITE_OLD_FILES:
-         {
-           int r = remove_any_file (file_name, ORDINARY_REMOVE_OPTION);
-           errno = EEXIST;
-           return r > 0 ? RECOVER_OK : RECOVER_NO;
-         }
+         if (0 < remove_any_file (file_name, ORDINARY_REMOVE_OPTION))
+           return RECOVER_OK;
+         break;
 
        case UNLINK_FIRST_OLD_FILES:
          break;
@@ -623,19 +644,20 @@ maybe_recoverable (char *file_name, bool *interdir_made)
 
     case ENOENT:
       /* Attempt creating missing intermediate directories.  */
-      if (! make_directories (file_name))
+      if (make_directories (file_name))
        {
-         errno = ENOENT;
-         return RECOVER_NO;
+         *interdir_made = true;
+         return RECOVER_OK;
        }
-      *interdir_made = true;
-      return RECOVER_OK;
+      break;
 
     default:
       /* Just say we can't do anything about it...  */
-
-      return RECOVER_NO;
+      break;
     }
+
+  errno = e;
+  return RECOVER_NO;
 }
 
 /* Fix the statuses of all directories whose statuses need fixing, and
@@ -769,7 +791,7 @@ extract_dir (char *file_name, int typeflag)
              || old_files_option == OVERWRITE_OLD_FILES))
        {
          struct stat st;
-         if (fstatat (chdir_fd, file_name, &st, 0) == 0)
+         if (deref_stat (file_name, &st) == 0)
            {
              current_mode = st.st_mode;
              current_mode_mask = ALL_MODE_BITS;
@@ -787,7 +809,7 @@ extract_dir (char *file_name, int typeflag)
          errno = EEXIST;
        }
 
-      switch (maybe_recoverable (file_name, &interdir_made))
+      switch (maybe_recoverable (file_name, false, &interdir_made))
        {
        case RECOVER_OK:
          continue;
@@ -823,8 +845,11 @@ open_output_file (char const *file_name, int typeflag, 
mode_t mode,
 {
   int fd;
   bool overwriting_old_files = old_files_option == OVERWRITE_OLD_FILES;
-  int openflag = (O_WRONLY | O_BINARY | O_CREAT
-                 | (overwriting_old_files ? O_TRUNC : O_EXCL));
+  int openflag = (O_WRONLY | O_BINARY | O_CLOEXEC | O_NOCTTY | O_NONBLOCK
+                 | O_CREAT
+                 | (overwriting_old_files
+                    ? O_TRUNC | (dereference_option ? 0 : O_NOFOLLOW)
+                    : O_EXCL));
 
   if (typeflag == CONTTYPE)
     {
@@ -898,21 +923,19 @@ extract_file (char *file_name, int typeflag)
     }
   else
     {
-      int recover = RECOVER_NO;
-      do
-       fd = open_output_file (file_name, typeflag, mode,
-                              &current_mode, &current_mode_mask);
-      while (fd < 0
-            && (recover = maybe_recoverable (file_name, &interdir_made))
-                == RECOVER_OK);
-
-      if (fd < 0)
+      while ((fd = open_output_file (file_name, typeflag, mode,
+                                    &current_mode, &current_mode_mask))
+            < 0)
        {
-         skip_member ();
-         if (recover == RECOVER_SKIP)
-           return 0;
-         open_error (file_name);
-         return 1;
+         int recover = maybe_recoverable (file_name, true, &interdir_made);
+         if (recover != RECOVER_OK)
+           {
+             skip_member ();
+             if (recover == RECOVER_SKIP)
+               return 0;
+             open_error (file_name);
+             return 1;
+           }
        }
     }
 
@@ -994,7 +1017,7 @@ create_placeholder_file (char *file_name, bool is_symlink, 
bool *interdir_made)
 
   while ((fd = openat (chdir_fd, file_name, O_WRONLY | O_CREAT | O_EXCL, 0)) < 
0)
     {
-      switch (maybe_recoverable (file_name, interdir_made))
+      switch (maybe_recoverable (file_name, false, interdir_made))
        {
        case RECOVER_OK:
          continue;
@@ -1106,7 +1129,8 @@ extract_link (char *file_name, int typeflag)
 
       errno = e;
     }
-  while ((rc = maybe_recoverable (file_name, &interdir_made)) == RECOVER_OK);
+  while ((rc = maybe_recoverable (file_name, false, &interdir_made))
+        == RECOVER_OK);
 
   if (rc == RECOVER_SKIP)
     return 0;
@@ -1130,7 +1154,7 @@ extract_symlink (char *file_name, int typeflag)
     return create_placeholder_file (file_name, true, &interdir_made);
 
   while (symlinkat (current_stat_info.link_name, chdir_fd, file_name) != 0)
-    switch (maybe_recoverable (file_name, &interdir_made))
+    switch (maybe_recoverable (file_name, false, &interdir_made))
       {
       case RECOVER_OK:
        continue;
@@ -1171,7 +1195,7 @@ extract_node (char *file_name, int typeflag)
 
   while (mknodat (chdir_fd, file_name, mode, current_stat_info.stat.st_rdev)
         != 0)
-    switch (maybe_recoverable (file_name, &interdir_made))
+    switch (maybe_recoverable (file_name, false, &interdir_made))
       {
       case RECOVER_OK:
        continue;
@@ -1200,7 +1224,7 @@ extract_fifo (char *file_name, int typeflag)
                 & ~ (0 < same_owner_option ? S_IRWXG | S_IRWXO : 0));
 
   while (mkfifoat (chdir_fd, file_name, mode) != 0)
-    switch (maybe_recoverable (file_name, &interdir_made))
+    switch (maybe_recoverable (file_name, false, &interdir_made))
       {
       case RECOVER_OK:
        continue;
@@ -1348,7 +1372,7 @@ prepare_to_extract (char const *file_name, int typeflag, 
tar_extractor_t *fun)
       break;
 
     case KEEP_NEWER_FILES:
-      if (file_newer_p (file_name, &current_stat_info))
+      if (file_newer_p (file_name, 0, &current_stat_info))
        {
          WARNOPT (WARN_IGNORE_NEWER,
                   (0, 0, _("Current %s is newer or same age"),
diff --git a/src/incremen.c b/src/incremen.c
index 4d86ed7..628ff29 100644
--- a/src/incremen.c
+++ b/src/incremen.c
@@ -408,7 +408,7 @@ update_parent_directory (struct tar_stat_info *parent)
   if (directory)
     {
       struct stat st;
-      if (fstatat (parent->fd, ".", &st, fstatat_flags) != 0)
+      if (fstat (parent->fd, &st) != 0)
        stat_diag (directory->name);
       else
        directory->mtime = get_stat_mtime (&st);
@@ -1668,7 +1668,7 @@ try_purge_directory (char const *directory_name)
        free (p);
       p = new_name (directory_name, cur);
 
-      if (deref_stat (false, p, &st))
+      if (deref_stat (p, &st) != 0)
        {
          if (errno != ENOENT) /* FIXME: Maybe keep a list of renamed
                                  dirs and check it here? */
diff --git a/src/misc.c b/src/misc.c
index d94791f..763c661 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -544,7 +544,7 @@ maybe_backup_file (const char *file_name, bool 
this_is_the_archive)
   if (this_is_the_archive && _remdev (file_name))
     return true;
 
-  if (fstatat (chdir_fd, file_name, &file_stat, 0))
+  if (deref_stat (file_name, &file_stat) != 0)
     {
       if (errno == ENOENT)
        return true;
@@ -608,24 +608,24 @@ undo_last_backup (void)
     }
 }
 
-/* Depending on DEREF, apply either stat or lstat to (NAME, BUF).  */
+/* Apply either stat or lstat to (NAME, BUF), depending on the
+   presence of the --dereference option.  NAME is relative to the
+   most-recent argument to chdir_do.  */
 int
-deref_stat (bool deref, char const *name, struct stat *buf)
+deref_stat (char const *name, struct stat *buf)
 {
-  return fstatat (chdir_fd, name, buf, deref ? 0 : AT_SYMLINK_NOFOLLOW);
+  return fstatat (chdir_fd, name, buf, fstatat_flags);
 }
 
 /* Set FD's (i.e., assuming the working directory is PARENTFD, FILE's)
-   access time to ATIME.  ATFLAG controls symbolic-link following, in
-   the style of openat.  */
+   access time to ATIME.  */
 int
-set_file_atime (int fd, int parentfd, char const *file, struct timespec atime,
-               int atflag)
+set_file_atime (int fd, int parentfd, char const *file, struct timespec atime)
 {
   struct timespec ts[2];
   ts[0] = atime;
   ts[1].tv_nsec = UTIME_OMIT;
-  return fdutimensat (fd, parentfd, file, ts, atflag);
+  return fdutimensat (fd, parentfd, file, ts, fstatat_flags);
 }
 
 /* A description of a working directory.  */
diff --git a/src/names.c b/src/names.c
index 88d8be2..6e214bf 100644
--- a/src/names.c
+++ b/src/names.c
@@ -981,7 +981,7 @@ collect_and_sort_names (void)
 
       tar_stat_init (&st);
 
-      if (deref_stat (dereference_option, name->name, &st.stat) != 0)
+      if (deref_stat (name->name, &st.stat) != 0)
        {
          stat_diag (name->name);
          continue;
@@ -1159,7 +1159,7 @@ register_individual_file (char const *name)
 {
   struct stat st;
 
-  if (deref_stat (dereference_option, name, &st) != 0)
+  if (deref_stat (name, &st) != 0)
     return; /* Will be complained about later */
   if (S_ISDIR (st.st_mode))
     return;
diff --git a/src/tar.c b/src/tar.c
index 6fd117c..d80a10f 100644
--- a/src/tar.c
+++ b/src/tar.c
@@ -1014,7 +1014,7 @@ get_date_or_file (struct tar_args *args, const char 
*option,
       || *str == '.')
     {
       struct stat st;
-      if (deref_stat (dereference_option, str, &st) != 0)
+      if (stat (str, &st) != 0)
        {
          stat_error (str);
          USAGE_ERROR ((0, 0, _("Date sample file not found")));
diff --git a/src/update.c b/src/update.c
index de2786d..69fa592 100644
--- a/src/update.c
+++ b/src/update.c
@@ -138,8 +138,7 @@ update_archive (void)
                struct stat s;
 
                chdir_do (name->change_dir);
-               if (deref_stat (dereference_option,
-                               current_stat_info.file_name, &s) == 0)
+               if (deref_stat (current_stat_info.file_name, &s) == 0)
                  {
                    if (S_ISDIR (s.st_mode))
                      {
diff --git a/tests/Makefile.am b/tests/Makefile.am
index d378a37..34be617 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -79,6 +79,7 @@ TESTSUITE_AT = \
  extrac10.at\
  extrac11.at\
  extrac12.at\
+ extrac13.at\
  filerem01.at\
  filerem02.at\
  gzip.at\
diff --git a/tests/extrac13.at b/tests/extrac13.at
new file mode 100644
index 0000000..2f950cb
--- /dev/null
+++ b/tests/extrac13.at
@@ -0,0 +1,53 @@
+# Process this file with autom4te to create testsuite. -*- Autotest -*-
+
+# Test suite for GNU tar.
+# Copyright (C) 2010 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# written by Paul Eggert
+
+# Check that 'tar' normally does follow symbolic links when extracting,
+# unless --dereference is specified.
+
+AT_SETUP([extract over symlinks])
+AT_KEYWORDS([extract extrac13])
+
+AT_TAR_CHECK([
+mkdir src dst1 dst2 dst3
+echo file1 >src/file1
+ln -s target1 dst1/file1
+echo target1 >dst1/target1
+echo target1 >target1
+
+tar -cf archive.tar -C src . &&
+tar -xf archive.tar -C dst1 &&
+diff -c src/file1 dst1/file1 &&
+diff -c target1 dst1/target1
+
+ln -s target1 dst2/file1
+echo target1 >dst2/target1
+tar --overwrite -xf archive.tar -C dst2 &&
+diff -c src/file1 dst2/file1 &&
+diff -c target1 dst2/target1
+
+ln -s target1 dst3/file1
+echo target1 >dst3/target1
+tar --overwrite -xhf archive.tar -C dst3 &&
+diff -c src/file1 dst3/file1 &&
+diff -c src/file1 dst3/target1
+],
+[0],[],[],[],[],[gnu])
+
+AT_CLEANUP
diff --git a/tests/testsuite.at b/tests/testsuite.at
index dc7a603..8d76887 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -151,6 +151,7 @@ m4_include([extrac09.at])
 m4_include([extrac10.at])
 m4_include([extrac11.at])
 m4_include([extrac12.at])
+m4_include([extrac13.at])
 
 m4_include([label01.at])
 m4_include([label02.at])
-- 
1.7.2