Fix some minor races in hosts lacking mkostemp.

Gnulib's emulation of mkostemp doesn't have races that Emacs's does.
* configure.ac (mkostemp): Remove check for this function;
gnulib does the check now.
(mkstemp): Remove check for this no-longer-used function.
* lib/mkostemp.c, lib/secure_getenv.c, lib/tempname.c, lib/tempname.h:
* m4/mkostemp.m4, m4/secure_getenv.m4, m4/tempname.m4:
New files, copied from Gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* admin/merge-gnulib (GNULIB_MODULES): Add mkostemp.
* lib-src/movemail.c (main):
* lib-src/update-game-score.c (write_scores):
Use mkostemp (which now works on all platforms, due to changes
in the portability layer) rather than mktemp (which has a race)
or mkstemp (which we no longer bother with).
* src/callproc.c (create_temp_file):
* src/filelock.c (create_lock_file):
Assume mkostemp, since it's now provided by Gnulib.

Fixes: debbugs:15015

1 files changed, 2 insertions, 16 deletions

diff --git a/src/filelock.c b/src/filelock.c
index b9c991e4baf..0f31b7d4deb 100644
--- a/src/filelock.c
+++ b/src/filelock.c
@@ -411,28 +411,14 @@ create_lock_file (char *lfname, char *lock_info_str, bool force)
       memcpy (nonce, lfname, lfdirlen);
       strcpy (nonce + lfdirlen, nonce_base);
 
-#if HAVE_MKOSTEMP
-      /* Prefer mkostemp to mkstemp, as it avoids a window where FD is
-	 temporarily open without close-on-exec.  */
       fd = mkostemp (nonce, O_BINARY | O_CLOEXEC);
-#elif HAVE_MKSTEMP
-      /* Prefer mkstemp to mktemp, as it avoids a race between
-	 mktemp and emacs_open.  */
-      fd = mkstemp (nonce);
-#else
-      mktemp (nonce);
-      fd = emacs_open (nonce, O_WRONLY | O_CREAT | O_EXCL | O_BINARY,
-		       S_IRUSR | S_IWUSR);
-#endif
-
       if (fd < 0)
 	err = errno;
       else
 	{
 	  ptrdiff_t lock_info_len;
-#if ! (HAVE_MKOSTEMP && O_CLOEXEC)
-	  fcntl (fd, F_SETFD, FD_CLOEXEC);
-#endif
+	  if (! O_CLOEXEC)
+	    fcntl (fd, F_SETFD, FD_CLOEXEC);
 	  lock_info_len = strlen (lock_info_str);
 	  err = 0;
 	  /* Use 'write', not 'emacs_write', as garbage collection