Commit: patch 9.1.0017: [security]: use-after-free in eval1_emsg()

[Christian Brabandt]

patch 9.1.0017: [security]: use-after-free in eval1_emsg()

Commit: https://github.com/vim/vim/commit/28d71b566a29ceea3a2d05bcee9264ed5d630d42
Author: Yegappan Lakshmanan <yega...@yahoo.com>
Date: Fri Jan 12 17:21:55 2024 +0100

patch 9.1.0017: [security]: use-after-free in eval1_emsg()

Problem: use-after-free in eval1_emsg() when an empty
line follows a lambda (by @yu3s)
Solution: only set evalarg->eval_using_cmdline = FALSE when
the *arg pointer is not null

fixes: #13833
closes: #13841

Signed-off-by: Yegappan Lakshmanan <yega...@yahoo.com>
Signed-off-by: Christian Brabandt <c...@256bit.org>

diff --git a/src/eval.c b/src/eval.c
index 815d13d42..bf053dfb6 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2699,6 +2699,9 @@ eval_next_non_blank(char_u *arg, evalarg_T *evalarg, int *getnext)
/*
* To be called after eval_next_non_blank() sets "getnext" to TRUE.
* Only called for Vim9 script.
+ *
+ * If "arg" is not NULL, then the caller should assign the return value to
+ * "arg".
*/
char_u *
eval_next_line(char_u *arg, evalarg_T *evalarg)
@@ -2747,8 +2750,12 @@ eval_next_line(char_u *arg, evalarg_T *evalarg)
}

// Advanced to the next line, "arg" no longer points into the previous
- // line.
- evalarg->eval_using_cmdline = FALSE;
+ // line. The caller assigns the return value to "arg".
+ // If "arg" is NULL, then the return value is discarded. In that case,
+ // "arg" still points to the previous line. So don't reset
+ // "eval_using_cmdline".
+ if (arg != NULL)
+ evalarg->eval_using_cmdline = FALSE;
return skipwhite(line);
}

diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 7ae4d553e..77b8831d4 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -4906,6 +4906,31 @@ def Test_for_stmt_space_before_type()
v9.CheckSourceFailure(lines, 'E1059: No white space allowed before colon: :number in range(10)', 2)
enddef

+" This test used to cause an use-after-free memory access
+def Test_for_empty_line_after_lambda()
+ var lines =<< trim END
+ vim9script
+ echomsg range(0, 2)->map((_, v) => {
+ return 1
+ })
+
+ assert_equal('[1, 1, 1]', v:statusmsg)
+ END
+ v9.CheckSourceSuccess(lines)
+
+ lines =<< trim END
+ vim9script
+ echomsg range(0, 1)->map((_, v) => {
+ return 1
+ }) range(0, 1)->map((_, v) => {
+ return 2
+ }) # comment
+
+ assert_equal('[1, 1] [2, 2]', v:statusmsg)
+ END
+ v9.CheckSourceSuccess(lines)
+enddef
+
" Keep this last, it messes up highlighting.
def Test_substitute_cmd()
new
diff --git a/src/version.c b/src/version.c
index 2e178f3bb..f440140a4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@ static char *(features[]) =

static int included_patches[] =
{ /* Add new patch number below this line */
+/**/
+ 17,
/**/
16,
/**/