Use SAFE_ALLOCA etc. to avoid unbounded stack allocation.

This follows up on the recent thread in emacs-devel on alloca; see:
http://lists.gnu.org/archive/html/emacs-devel/2014-09/msg00042.html
This patch also cleans up alloca-related glitches noted while
examining the code looking for unbounded alloca.
* alloc.c (listn):
* callproc.c (init_callproc):
Rewrite to avoid need for alloca.
* buffer.c (mouse_face_overlay_overlaps)
(report_overlay_modification):
* buffer.h (GET_OVERLAYS_AT):
* coding.c (make_subsidiaries):
* doc.c (Fsnarf_documentation):
* editfns.c (Fuser_full_name):
* fileio.c (Ffile_name_directory, Fexpand_file_name)
(search_embedded_absfilename, Fsubstitute_in_file_name):
* fns.c (Fmake_hash_table):
* font.c (font_vconcat_entity_vectors, font_update_drivers):
* fontset.c (fontset_pattern_regexp, Ffontset_info):
* frame.c (Fmake_terminal_frame, x_set_frame_parameters)
(xrdb_get_resource, x_get_resource_string):
* ftfont.c (ftfont_get_charset, ftfont_check_otf, ftfont_drive_otf):
* ftxfont.c (ftxfont_draw):
* image.c (xbm_load, xpm_load, jpeg_load_body):
* keyboard.c (echo_add_key, menu_bar_items, tool_bar_items):
* keymap.c (Fdescribe_buffer_bindings, describe_map):
* lread.c (openp):
* menu.c (digest_single_submenu, find_and_call_menu_selection)
(find_and_return_menu_selection):
* print.c (PRINTFINISH):
* process.c (Fformat_network_address):
* scroll.c (do_scrolling, do_direct_scrolling, scrolling_1):
* search.c (search_buffer, Fmatch_data, Fregexp_quote):
* sound.c (wav_play, au_play):
* syntax.c (skip_chars):
* term.c (tty_menu_activate, tty_menu_show):
* textprop.c (get_char_property_and_overlay):
* window.c (Fset_window_configuration):
* xdisp.c (safe__call, next_overlay_change, vmessage)
(compute_overhangs_and_x, draw_glyphs, note_mouse_highlight):
* xfaces.c (face_at_buffer_position):
* xmenu.c (x_menu_show):
Use SAFE_ALLOCA etc. instead of plain alloca, since the
allocation size isn't bounded.
* callint.c (Fcall_interactively): Redo memory_full check
so that it can be done at compile-time on some platforms.
* coding.c (MAX_LOOKUP_MAX): New constant.
(get_translation_table): Use it.
* callproc.c (call_process): Use SAFE_NALLOCA instead of
SAFE_ALLOCA, to catch integer overflows on size calculation.
(exec_failed) [!DOS_NT]: New function.
(child_setup) [!DOS_NT]: Use it.
* editfns.c (Ftranspose_regions):
Hoist USE_SAFE_ALLOC + SAFE_FREE out of 'if'.
* editfns.c (check_translation):
Allocate larger buffers on the heap.
* eval.c (internal_lisp_condition_case):
Check for MAX_ALLOCA overflow.
* fns.c (sort_vector): Use SAFE_ALLOCA_LISP rather than Fmake_vector.
(Fbase64_encode_region, Fbase64_decode_region):
Avoid unnecessary calls to SAFE_FREE before 'error'.
* buffer.c (mouse_face_overlay_overlaps):
* editfns.c (Fget_pos_property, check_translation):
* eval.c (Ffuncall):
* font.c (font_unparse_xlfd, font_find_for_lface):
* ftfont.c (ftfont_drive_otf):
* keyboard.c (echo_add_key, read_decoded_event_from_main_queue)
(menu_bar_items, tool_bar_items):
* sound.c (Fplay_sound_internal):
* xdisp.c (load_overlay_strings, dump_glyph_row):
Use an ordinary auto buffer rather than alloca, since the
allocation size is fixed and small.
* ftfont.c: Include <c-strcase.h>.
(matching_prefix): New function.
(get_adstyle_property): Use it, to avoid need for alloca.
* keyboard.c (echo_add_key):
* keymap.c (describe_map): Use ptrdiff_t, not int.
* keyboard.c (echo_add_key): Prefer sizeof to strlen.
* keymap.c (Fdescribe_buffer_bindings): Use SBYTES, not SCHARS,
when counting bytes.
* lisp.h (xlispstrdupa): Remove, replacing with ...
(SAFE_ALLOCA_STRING): ... new macro with different API.
This fixes a portability problem, namely, alloca result
passed to another function.  All uses changed.
(SAFE_ALLOCA, SAFE_ALLOCA_LISP): Check for MAX_ALLOCA,
not MAX_ALLOCA - 1.
* regex.c (REGEX_USE_SAFE_ALLOCA, REGEX_SAFE_FREE)
(REGEX_ALLOCATE): New macros.
(REGEX_REALLOCATE, REGEX_ALLOCATE_STACK, REGEX_REALLOCATE_STACK)
(REGEX_FREE_STACK, FREE_VARIABLES, re_match_2_internal):
Use them.
* xdisp.c (message3): Use SAFE_ALLOCA_STRING rather than doing it
by hand.
(decode_mode_spec_coding): Store directly into buf rather than
into an alloca temporary and copying the temporary to the buf.

Fixes: debbugs:18410

1 files changed, 10 insertions, 3 deletions

diff --git a/src/coding.c b/src/coding.c
index 8b620af8695..84b774b4355 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -6867,6 +6867,11 @@ decode_eol (struct coding_system *coding)
 }
 
 
+/* MAX_LOOKUP's maximum value.  MAX_LOOKUP is an int and so cannot
+   exceed INT_MAX.  Also, MAX_LOOKUP is multiplied by sizeof (int) for
+   alloca, so it cannot exceed MAX_ALLOCA / sizeof (int).  */
+enum { MAX_LOOKUP_MAX = min (INT_MAX, MAX_ALLOCA / sizeof (int)) };
+
 /* Return a translation table (or list of them) from coding system
    attribute vector ATTRS for encoding (if ENCODEP) or decoding (if
    not ENCODEP). */
@@ -6919,7 +6924,7 @@ get_translation_table (Lisp_Object attrs, bool encodep, int *max_lookup)
 	{
 	  val = XCHAR_TABLE (translation_table)->extras[1];
 	  if (NATNUMP (val) && *max_lookup < XFASTINT (val))
-	    *max_lookup = XFASTINT (val);
+	    *max_lookup = min (XFASTINT (val), MAX_LOOKUP_MAX);
 	}
       else if (CONSP (translation_table))
 	{
@@ -6931,7 +6936,7 @@ get_translation_table (Lisp_Object attrs, bool encodep, int *max_lookup)
 	      {
 		Lisp_Object tailval = XCHAR_TABLE (XCAR (tail))->extras[1];
 		if (NATNUMP (tailval) && *max_lookup < XFASTINT (tailval))
-		  *max_lookup = XFASTINT (tailval);
+		  *max_lookup = min (XFASTINT (tailval), MAX_LOOKUP_MAX);
 	      }
 	}
     }
@@ -10011,7 +10016,8 @@ make_subsidiaries (Lisp_Object base)
 {
   Lisp_Object subsidiaries;
   ptrdiff_t base_name_len = SBYTES (SYMBOL_NAME (base));
-  char *buf = alloca (base_name_len + 6);
+  USE_SAFE_ALLOCA;
+  char *buf = SAFE_ALLOCA (base_name_len + 6);
   int i;
 
   memcpy (buf, SDATA (SYMBOL_NAME (base)), base_name_len);
@@ -10021,6 +10027,7 @@ make_subsidiaries (Lisp_Object base)
       strcpy (buf + base_name_len, suffixes[i]);
       ASET (subsidiaries, i, intern (buf));
     }
+  SAFE_FREE ();
   return subsidiaries;
 }