Fix some minor file descriptor leaks and related glitches.

* filelock.c (create_lock_file) [!O_CLOEXEC]: Use fcntl with FD_CLOEXEC.
(create_lock_file): Use write, not emacs_write.
* image.c (slurp_file, png_load_body):
* process.c (Fnetwork_interface_list, Fnetwork_interface_info)
(server_accept_connection):
Don't leak an fd on memory allocation failure.
* image.c (slurp_file): Add a cheap heuristic for growing files.
* xfaces.c (Fx_load_color_file): Block input around the fopen too,
as that's what the other routines do.  Maybe input need not be
blocked at all, but it's better to be consistent.
Avoid undefined behavior when strlen is zero.

src/ChangeLog

@@ -1,5 +1,18 @@
 2013-07-19  Paul Eggert  <eggert@cs.ucla.edu>
 
+	Fix some minor file descriptor leaks and related glitches.
+	* filelock.c (create_lock_file) [!O_CLOEXEC]: Use fcntl with FD_CLOEXEC.
+	(create_lock_file): Use write, not emacs_write.
+	* image.c (slurp_file, png_load_body):
+	* process.c (Fnetwork_interface_list, Fnetwork_interface_info)
+	(server_accept_connection):
+	Don't leak an fd on memory allocation failure.
+	* image.c (slurp_file): Add a cheap heuristic for growing files.
+	* xfaces.c (Fx_load_color_file): Block input around the fopen too,
+	as that's what the other routines do.  Maybe input need not be
+	blocked at all, but it's better to be consistent.
+	Avoid undefined behavior when strlen is zero.
+
 	* alloc.c (staticpro): Avoid buffer overrun on repeated calls.
 	(NSTATICS): Now a constant; doesn't need to be a macro.
 

src/filelock.c

@@ -430,12 +430,14 @@ create_lock_file (char *lfname, char *lock_info_str, bool force)
       else
 	{
 	  ptrdiff_t lock_info_len;
-#if ! HAVE_MKOSTEMP
+#if ! (HAVE_MKOSTEMP && O_CLOEXEC)
 	  fcntl (fd, F_SETFD, FD_CLOEXEC);
 #endif
 	  lock_info_len = strlen (lock_info_str);
 	  err = 0;
-	  if (emacs_write (fd, lock_info_str, lock_info_len) != lock_info_len
+	  /* Use 'write', not 'emacs_write', as garbage collection
+	     might signal an error, which would leak FD.  */
+	  if (write (fd, lock_info_str, lock_info_len) != lock_info_len
 	      || fchmod (fd, S_IRUSR | S_IRGRP | S_IROTH) != 0)
 	    err = errno;
 	  /* There is no need to call fsync here, as the contents of

src/image.c

@@ -2276,23 +2276,28 @@ slurp_file (char *file, ptrdiff_t *size)
   unsigned char *buf = NULL;
   struct stat st;
 
-  if (fp && fstat (fileno (fp), &st) == 0
-      && 0 <= st.st_size && st.st_size <= min (PTRDIFF_MAX, SIZE_MAX)
-      && (buf = xmalloc (st.st_size),
-	  fread (buf, 1, st.st_size, fp) == st.st_size))
+  if (fp)
     {
-      *size = st.st_size;
-      fclose (fp);
-    }
-  else
-    {
-      if (fp)
-	fclose (fp);
-      if (buf)
+      ptrdiff_t count = SPECPDL_INDEX ();
+      record_unwind_protect_ptr (fclose_unwind, fp);
+
+      if (fstat (fileno (fp), &st) == 0
+	  && 0 <= st.st_size && st.st_size < min (PTRDIFF_MAX, SIZE_MAX))
 	{
-	  xfree (buf);
-	  buf = NULL;
+	  /* Report an error if we read past the purported EOF.
+	     This can happen if the file grows as we read it.  */
+	  ptrdiff_t buflen = st.st_size;
+	  buf = xmalloc (buflen + 1);
+	  if (fread (buf, 1, buflen + 1, fp) == buflen)
+	    *size = buflen;
+	  else
+	    {
+	      xfree (buf);
+	      buf = NULL;
+	    }
 	}
+
+      unbind_to (count, Qnil);
     }
 
   return buf;
@@ -5732,8 +5737,8 @@ png_load_body (struct frame *f, struct image *img, struct png_load_context *c)
       if (fread (sig, 1, sizeof sig, fp) != sizeof sig
 	  || fn_png_sig_cmp (sig, 0, sizeof sig))
 	{
-	  image_error ("Not a PNG file: `%s'", file, Qnil);
 	  fclose (fp);
+	  image_error ("Not a PNG file: `%s'", file, Qnil);
 	  return 0;
 	}
     }

src/process.c

@@ -3526,10 +3526,13 @@ format; see the description of ADDRESS in `make-network-process'.  */)
   ptrdiff_t buf_size = 512;
   int s;
   Lisp_Object res;
+  ptrdiff_t count;
 
   s = socket (AF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0);
   if (s < 0)
     return Qnil;
+  count = SPECPDL_INDEX ();
+  record_unwind_protect_int (close_file_unwind, s);
 
   do
     {
@@ -3545,9 +3548,7 @@ format; see the description of ADDRESS in `make-network-process'.  */)
     }
   while (ifconf.ifc_len == buf_size);
 
-  emacs_close (s);
-
-  res = Qnil;
+  res = unbind_to (count, Qnil);
   ifreq = ifconf.ifc_req;
   while ((char *) ifreq < (char *) ifconf.ifc_req + ifconf.ifc_len)
     {
@@ -3672,6 +3673,7 @@ FLAGS is the current flags of the interface.  */)
   Lisp_Object elt;
   int s;
   bool any = 0;
+  ptrdiff_t count;
 #if (! (defined SIOCGIFHWADDR && defined HAVE_STRUCT_IFREQ_IFR_HWADDR)	\
      && defined HAVE_GETIFADDRS && defined LLADDR)
   struct ifaddrs *ifap;
@@ -3686,6 +3688,8 @@ FLAGS is the current flags of the interface.  */)
   s = socket (AF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0);
   if (s < 0)
     return Qnil;
+  count = SPECPDL_INDEX ();
+  record_unwind_protect_int (close_file_unwind, s);
 
   elt = Qnil;
 #if defined (SIOCGIFFLAGS) && defined (HAVE_STRUCT_IFREQ_IFR_FLAGS)
@@ -3802,9 +3806,7 @@ FLAGS is the current flags of the interface.  */)
 #endif
   res = Fcons (elt, res);
 
-  emacs_close (s);
-
-  return any ? res : Qnil;
+  return unbind_to (count, any ? res : Qnil);
 }
 #endif
 #endif	/* defined (HAVE_NET_IF_H) */
@@ -3978,6 +3980,7 @@ server_accept_connection (Lisp_Object server, int channel)
 #endif
   } saddr;
   socklen_t len = sizeof saddr;
+  ptrdiff_t count;
 
   s = accept4 (channel, &saddr.sa, &len, SOCK_CLOEXEC);
 
@@ -4000,6 +4003,9 @@ server_accept_connection (Lisp_Object server, int channel)
       return;
     }
 
+  count = SPECPDL_INDEX ();
+  record_unwind_protect_int (close_file_unwind, s);
+
   connect_counter++;
 
   /* Setup a new process to handle the connection.  */
@@ -4116,6 +4122,10 @@ server_accept_connection (Lisp_Object server, int channel)
   pset_filter (p, ps->filter);
   pset_command (p, Qnil);
   p->pid = 0;
+
+  /* Discard the unwind protect for closing S.  */
+  specpdl_ptr = specpdl + count;
+
   p->infd  = s;
   p->outfd = s;
   pset_status (p, Qrun);

src/xfaces.c

@@ -6283,6 +6283,7 @@ where R,G,B are numbers between 0 and 255 and name is an arbitrary string.  */)
   CHECK_STRING (filename);
   abspath = Fexpand_file_name (filename, Qnil);
 
+  block_input ();
   fp = emacs_fopen (SSDATA (abspath), "rt");
   if (fp)
     {
@@ -6290,29 +6291,24 @@ where R,G,B are numbers between 0 and 255 and name is an arbitrary string.  */)
       int red, green, blue;
       int num;
 
-      block_input ();
-
       while (fgets (buf, sizeof (buf), fp) != NULL) {
 	if (sscanf (buf, "%u %u %u %n", &red, &green, &blue, &num) == 3)
 	  {
-	    char *name = buf + num;
-	    num = strlen (name) - 1;
-	    if (num >= 0 && name[num] == '\n')
-	      name[num] = 0;
-	    cmap = Fcons (Fcons (build_string (name),
 #ifdef HAVE_NTGUI
-				 make_number (RGB (red, green, blue))),
+	    int color = RGB (red, green, blue);
 #else
-				 make_number ((red << 16) | (green << 8) | blue)),
+	    int color = (red << 16) | (green << 8) | blue;
 #endif
+	    char *name = buf + num;
+	    ptrdiff_t len = strlen (name);
+	    len -= 0 < len && name[len - 1] == '\n';
+	    cmap = Fcons (Fcons (make_string (name, len), make_number (color)),
 			  cmap);
 	  }
       }
       fclose (fp);
-
-      unblock_input ();
     }
-
+  unblock_input ();
   return cmap;
 }
 #endif