[for-next][PATCH 4/5] ktest.pl: Prevent recursion of default variable options

[Steven Rostedt <rostedt@kernel.org>]

From: Steven Rostedt <rostedt@goodmis.org>

If a default variable contains itself, do not recurse on it.

For example:

  ADD_CONFIG := ${CONFIG_DIR}/temp_config
  DEFAULTS
  ADD_CONFIG = ${CONFIG_DIR}/default_config ${ADD_CONFIG}

The above works because the temp variable ADD_CONFIG (is a temp because it
is created with ":=") is already defined, it will be substituted in the
variable option. But if it gets commented out:

  # ADD_CONFIG := ${CONFIG_DIR}/temp_config
  DEFAULTS
  ADD_CONFIG = ${CONFIG_DIR}/default_config ${ADD_CONFIG}

Then the above will go into a recursive loop where ${ADD_CONFIG} will
get replaced with the current definition of ADD_CONFIG which contains the
${ADD_CONFIG} and that will also try to get converted. ktest.pl will error
after 100 attempts of recursion and fail.

When replacing a variable with the default variable, if the default
variable contains itself, do not replace it.

Cc: "John Warthog9 Hawley" <warthog9@kernel.org>
Cc: Dhaval Giani <dhaval.giani@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/20250718202053.732189428@kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 tools/testing/ktest/ktest.pl | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/testing/ktest/ktest.pl b/tools/testing/ktest/ktest.pl
index 95e62929cda7..3a679259f4e2 100755
--- a/tools/testing/ktest/ktest.pl
+++ b/tools/testing/ktest/ktest.pl
@@ -1394,7 +1394,10 @@ sub __eval_option {
 	# If a variable contains itself, use the default var
 	if (($var eq $name) && defined($opt{$var})) {
 	    $o = $opt{$var};
-	    $retval = "$retval$o";
+	    # Only append if the default doesn't contain itself
+	    if ($o !~ m/\$\{$var\}/) {
+		$retval = "$retval$o";
+	    }
 	} elsif (defined($opt{$o})) {
 	    $o = $opt{$o};
 	    $retval = "$retval$o";
-- 
2.47.2