patch 9.2.0276: [security]: modeline security bypass

Problem:  [security]: modeline security bypass
Solution: disallow mapset() from secure mode, set the P_MLE flag for the
          'complete', 'guitabtooltip' and 'printheader' options.

Github Advisory:
GHSA-8h6p-m6gr-mpw9

Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: chrisbra

src/map.c

@@ -2746,6 +2746,9 @@ f_mapset(typval_T *argvars, typval_T *rettv UNUSED)
     int		dict_only;
     mapblock_T	*mp_result[2] = {NULL, NULL};
 
+    if (check_secure())
+	return;
+
     // If first arg is a dict, then that's the only arg permitted.
     dict_only = argvars[0].v_type == VAR_DICT;
     if (in_vim9script()

src/optiondefs.h

@@ -681,7 +681,7 @@ static struct vimoption options[] =
     {"compatible",  "cp",   P_BOOL|P_RALL,
 			    (char_u *)&p_cp, PV_NONE, did_set_compatible, NULL,
 			    {(char_u *)TRUE, (char_u *)FALSE} SCTX_INIT},
-    {"complete",    "cpt",  P_STRING|P_ALLOCED|P_VI_DEF|P_ONECOMMA|P_NODUP,
+    {"complete",    "cpt",  P_STRING|P_ALLOCED|P_VI_DEF|P_ONECOMMA|P_NODUP|P_MLE,
 			    (char_u *)&p_cpt, PV_CPT, did_set_complete, expand_set_complete,
 			    {(char_u *)".,w,b,u,t,i", (char_u *)0L}
 			    SCTX_INIT},
@@ -1324,7 +1324,7 @@ static struct vimoption options[] =
 			    {(char_u *)NULL, (char_u *)0L}
 #endif
 			    SCTX_INIT},
-    {"guitabtooltip",  "gtt", P_STRING|P_VI_DEF|P_RWIN,
+    {"guitabtooltip",  "gtt", P_STRING|P_VI_DEF|P_RWIN|P_MLE,
 #if defined(FEAT_GUI_TABLINE)
 			    (char_u *)&p_gtt, PV_NONE, NULL, NULL,
 			    {(char_u *)"", (char_u *)0L}
@@ -2041,7 +2041,7 @@ static struct vimoption options[] =
 			    {(char_u *)NULL, (char_u *)0L}
 #endif
 			    SCTX_INIT},
-    {"printheader", "pheader",  P_STRING|P_VI_DEF|P_GETTEXT,
+    {"printheader", "pheader",  P_STRING|P_VI_DEF|P_GETTEXT|P_MLE,
 #ifdef FEAT_PRINTER
 			    (char_u *)&p_header, PV_NONE, NULL, NULL,
 			    // untranslated to avoid problems when 'encoding'

src/testdir/test_modeline.vim

@@ -490,4 +490,29 @@ func Test_modeline_nowrap_lcs_extends()
   set equalalways&
 endfunc
 
+func Test_modeline_forbidden()
+  let tempfile = tempname()
+  let lines =<< trim END
+    some test text for completion
+    vim: set complete=F{->system('touch_should_not_run')} :
+  END
+  call writefile(lines, tempfile, 'D')
+  call assert_fails($'new {tempfile}', 'E992:')
+  bw!
+  let lines =<< trim END
+    some text
+    vim: set guitabtooltip=%{%mapset()%}:
+  END
+  call writefile(lines, tempfile)
+  call assert_fails($'new {tempfile}', 'E992:')
+  bw!
+  let lines =<< trim END
+    some text
+    vim: set printheader=%{mapset('n',0,{})%)%}:
+  END
+  call writefile(lines, tempfile, 'D')
+  call assert_fails($'new {tempfile}', 'E992:')
+  bw!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    276,
 /**/
     275,
 /**/