From 91c7cbfe31bbef57d5fcf7d76989fc159f73ef15 Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Thu, 18 Aug 2022 13:28:31 +0100
Subject: [PATCH] patch 9.0.0225: using freed memory with multiple line breaks
 in expression

Problem:    Using freed memory with multiple line breaks in expression.
Solution:   Free eval_tofree later.
---
 src/eval.c                       | 102 ++++++++++++++++++-------------
 src/proto/eval.pro               |   4 +-
 src/testdir/test_vim9_script.vim |  13 ++++
 src/userfunc.c                   |  15 -----
 4 files changed, 75 insertions(+), 59 deletions(-)

diff --git a/src/eval.c b/src/eval.c
index 42b883e..60daca5 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -353,6 +353,63 @@ eval_to_string_skip(
     return retval;
 }
 
+/*
+ * Initialize "evalarg" for use.
+ */
+    void
+init_evalarg(evalarg_T *evalarg)
+{
+    CLEAR_POINTER(evalarg);
+    ga_init2(&evalarg->eval_tofree_ga, sizeof(char_u *), 20);
+}
+
+/*
+ * If "evalarg->eval_tofree" is not NULL free it later.
+ * Caller is expected to overwrite "evalarg->eval_tofree" next.
+ */
+    static void
+free_eval_tofree_later(evalarg_T *evalarg)
+{
+    if (evalarg->eval_tofree != NULL)
+    {
+	if (ga_grow(&evalarg->eval_tofree_ga, 1) == OK)
+	    ((char_u **)evalarg->eval_tofree_ga.ga_data)
+		[evalarg->eval_tofree_ga.ga_len++]
+		= evalarg->eval_tofree;
+	else
+	    vim_free(evalarg->eval_tofree);
+    }
+}
+
+/*
+ * After using "evalarg" filled from "eap": free the memory.
+ */
+    void
+clear_evalarg(evalarg_T *evalarg, exarg_T *eap)
+{
+    if (evalarg != NULL)
+    {
+	if (evalarg->eval_tofree != NULL)
+	{
+	    if (eap != NULL)
+	    {
+		// We may need to keep the original command line, e.g. for
+		// ":let" it has the variable names.  But we may also need the
+		// new one, "nextcmd" points into it.  Keep both.
+		vim_free(eap->cmdline_tofree);
+		eap->cmdline_tofree = *eap->cmdlinep;
+		*eap->cmdlinep = evalarg->eval_tofree;
+	    }
+	    else
+		vim_free(evalarg->eval_tofree);
+	    evalarg->eval_tofree = NULL;
+	}
+
+	ga_clear_strings(&evalarg->eval_tofree_ga);
+	VIM_CLEAR(evalarg->eval_tofree_lambda);
+    }
+}
+
 /*
  * Skip over an expression at "*pp".
  * Return FAIL for an error, OK otherwise.
@@ -435,8 +492,8 @@ skip_expr_concatenate(
 		// Do not free the first line, the caller can still use it.
 		*((char_u **)gap->ga_data) = NULL;
 		// Do not free the last line, "arg" points into it, free it
-		// later.
-		vim_free(evalarg->eval_tofree);
+		// later.  Also free "eval_tofree" later if needed.
+		free_eval_tofree_later(evalarg);
 		evalarg->eval_tofree =
 				    ((char_u **)gap->ga_data)[gap->ga_len - 1];
 		((char_u **)gap->ga_data)[gap->ga_len - 1] = NULL;
@@ -2274,7 +2331,7 @@ eval_next_line(char_u *arg, evalarg_T *evalarg)
     }
     else if (evalarg->eval_cookie != NULL)
     {
-	vim_free(evalarg->eval_tofree);
+	free_eval_tofree_later(evalarg);
 	evalarg->eval_tofree = line;
     }
 
@@ -2301,45 +2358,6 @@ skipwhite_and_linebreak(char_u *arg, evalarg_T *evalarg)
     return p;
 }
 
-/*
- * Initialize "evalarg" for use.
- */
-    void
-init_evalarg(evalarg_T *evalarg)
-{
-    CLEAR_POINTER(evalarg);
-    ga_init2(&evalarg->eval_tofree_ga, sizeof(char_u *), 20);
-}
-
-/*
- * After using "evalarg" filled from "eap": free the memory.
- */
-    void
-clear_evalarg(evalarg_T *evalarg, exarg_T *eap)
-{
-    if (evalarg != NULL)
-    {
-	if (evalarg->eval_tofree != NULL)
-	{
-	    if (eap != NULL)
-	    {
-		// We may need to keep the original command line, e.g. for
-		// ":let" it has the variable names.  But we may also need the
-		// new one, "nextcmd" points into it.  Keep both.
-		vim_free(eap->cmdline_tofree);
-		eap->cmdline_tofree = *eap->cmdlinep;
-		*eap->cmdlinep = evalarg->eval_tofree;
-	    }
-	    else
-		vim_free(evalarg->eval_tofree);
-	    evalarg->eval_tofree = NULL;
-	}
-
-	ga_clear_strings(&evalarg->eval_tofree_ga);
-	VIM_CLEAR(evalarg->eval_tofree_lambda);
-    }
-}
-
 /*
  * The "evaluate" argument: When FALSE, the argument is only parsed but not
  * executed.  The function may return OK, but the rettv will be of type
diff --git a/src/proto/eval.pro b/src/proto/eval.pro
index e6cd892..27a13c9 100644
--- a/src/proto/eval.pro
+++ b/src/proto/eval.pro
@@ -9,6 +9,8 @@ int eval_expr_valid_arg(typval_T *tv);
 int eval_expr_typval(typval_T *expr, typval_T *argv, int argc, typval_T *rettv);
 int eval_expr_to_bool(typval_T *expr, int *error);
 char_u *eval_to_string_skip(char_u *arg, exarg_T *eap, int skip);
+void init_evalarg(evalarg_T *evalarg);
+void clear_evalarg(evalarg_T *evalarg, exarg_T *eap);
 int skip_expr(char_u **pp, evalarg_T *evalarg);
 int skip_expr_concatenate(char_u **arg, char_u **start, char_u **end, evalarg_T *evalarg);
 char_u *typval2string(typval_T *tv, int convert);
@@ -34,8 +36,6 @@ int pattern_match(char_u *pat, char_u *text, int ic);
 char_u *eval_next_non_blank(char_u *arg, evalarg_T *evalarg, int *getnext);
 char_u *eval_next_line(char_u *arg, evalarg_T *evalarg);
 char_u *skipwhite_and_linebreak(char_u *arg, evalarg_T *evalarg);
-void init_evalarg(evalarg_T *evalarg);
-void clear_evalarg(evalarg_T *evalarg, exarg_T *eap);
 int eval0(char_u *arg, typval_T *rettv, exarg_T *eap, evalarg_T *evalarg);
 int eval0_retarg(char_u *arg, typval_T *rettv, exarg_T *eap, evalarg_T *evalarg, char_u **retarg);
 int eval1(char_u **arg, typval_T *rettv, evalarg_T *evalarg);
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 75b3e9c..c09c0d2 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -1560,6 +1560,19 @@ def Test_func_redefine_fails()
   v9.CheckScriptFailure(lines, 'E1073:')
 enddef
 
+def Test_lambda_split()
+  # this was using freed memory, because of the split expression
+  var lines =<< trim END
+      vim9script
+      try
+      0
+      0->(0
+        ->a.0(
+        ->u
+  END
+  v9.CheckScriptFailure(lines, 'E1050:')
+enddef
+
 def Test_fixed_size_list()
   # will be allocated as one piece of memory, check that changes work
   var l = [1, 2, 3, 4]
diff --git a/src/userfunc.c b/src/userfunc.c
index 9b960b7..3777e03 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -1371,7 +1371,6 @@ get_lambda_tv(
     char_u	*start, *end;
     int		*old_eval_lavars = eval_lavars_used;
     int		eval_lavars = FALSE;
-    char_u	*tofree1 = NULL;
     char_u	*tofree2 = NULL;
     int		equal_arrow = **arg == '(';
     int		white_error = FALSE;
@@ -1456,12 +1455,6 @@ get_lambda_tv(
     ret = skip_expr_concatenate(arg, &start, &end, evalarg);
     if (ret == FAIL)
 	goto errret;
-    if (evalarg != NULL)
-    {
-	// avoid that the expression gets freed when another line break follows
-	tofree1 = evalarg->eval_tofree;
-	evalarg->eval_tofree = NULL;
-    }
 
     if (!equal_arrow)
     {
@@ -1584,10 +1577,6 @@ get_lambda_tv(
 
 theend:
     eval_lavars_used = old_eval_lavars;
-    if (evalarg != NULL && evalarg->eval_tofree == NULL)
-	evalarg->eval_tofree = tofree1;
-    else
-	vim_free(tofree1);
     vim_free(tofree2);
     if (types_optional)
 	ga_clear_strings(&argtypes);
@@ -1606,10 +1595,6 @@ errret:
     }
     vim_free(fp);
     vim_free(pt);
-    if (evalarg != NULL && evalarg->eval_tofree == NULL)
-	evalarg->eval_tofree = tofree1;
-    else
-	vim_free(tofree1);
     vim_free(tofree2);
     eval_lavars_used = old_eval_lavars;
     return FAIL;
-- 
2.36.1