Fix bug #12867 with crashes due to large field width in mode-line format.

 src/xdisp.c (decode_mode_spec): Limit the value of WIDTH argument
 passed to pint2str and pint2hrstr to be at most the size of the
 frame's decode_mode_spec_buffer.  This avoids crashes with very
 large values of FIELD_WIDTH argument to decode_mode_spec.

diff --git a/src/ChangeLog b/src/ChangeLog
index 9e0f92f..494b217 100644 (file)
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,11 @@
+2012-11-12  Eli Zaretskii  <eliz@gnu.org>
+
+       * xdisp.c (decode_mode_spec): Limit the value of WIDTH argument
+       passed to pint2str and pint2hrstr to be at most the size of the
+       frame's decode_mode_spec_buffer.  This avoids crashes with very
+       large values of FIELD_WIDTH argument to decode_mode_spec.
+       (Bug#12867)
+
 2012-11-07  Martin Rudalics  <rudalics@gmx.at>
 
        * window.c (Fsplit_window_internal): Set combination limit of

diff --git a/src/xdisp.c b/src/xdisp.c
index c719550..290c3a0 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -21380,6 +21380,12 @@ decode_mode_spec (struct window *w, register int c, int field_width,
   Lisp_Object obj;
   struct frame *f = XFRAME (WINDOW_FRAME (w));
   char *decode_mode_spec_buf = f->decode_mode_spec_buffer;
+  /* We are going to use f->decode_mode_spec_buffer as the buffer to
+     produce strings from numerical values, so limit preposterously
+     large values of FIELD_WIDTH to avoid overrunning the buffer's
+     end.  The size of the buffer is enough for FRAME_MESSAGE_BUF_SIZE
+     bytes plus the terminating null.  */
+  int width = min (field_width, FRAME_MESSAGE_BUF_SIZE (f));
   struct buffer *b = current_buffer;
 
   obj = Qnil;
@@ -21475,7 +21481,7 @@ decode_mode_spec (struct window *w, register int c, int field_width,
        {
          ptrdiff_t col = current_column ();
          wset_column_number_displayed (w, make_number (col));
-         pint2str (decode_mode_spec_buf, field_width, col);
+         pint2str (decode_mode_spec_buf, width, col);
          return decode_mode_spec_buf;
        }
 
@@ -21506,14 +21512,14 @@ decode_mode_spec (struct window *w, register int c, int field_width,
     case 'i':
       {
        ptrdiff_t size = ZV - BEGV;
-       pint2str (decode_mode_spec_buf, field_width, size);
+       pint2str (decode_mode_spec_buf, width, size);
        return decode_mode_spec_buf;
       }
 
     case 'I':
       {
        ptrdiff_t size = ZV - BEGV;
-       pint2hrstr (decode_mode_spec_buf, field_width, size);
+       pint2hrstr (decode_mode_spec_buf, width, size);
        return decode_mode_spec_buf;
       }
 
@@ -21620,12 +21626,12 @@ decode_mode_spec (struct window *w, register int c, int field_width,
        line_number_displayed = 1;
 
        /* Make the string to show.  */
-       pint2str (decode_mode_spec_buf, field_width, topline + nlines);
+       pint2str (decode_mode_spec_buf, width, topline + nlines);
        return decode_mode_spec_buf;
     no_value:
         {
          char* p = decode_mode_spec_buf;
-         int pad = field_width - 2;
+         int pad = width - 2;
          while (pad-- > 0)
            *p++ = ' ';
          *p++ = '?';