configs/hardening: Enable CONFIG_INIT_ON_FREE_DEFAULT_ON

To reduce stale data lifetimes, enable CONFIG_INIT_ON_FREE_DEFAULT_ON as
well. This matches the addition of CONFIG_STACKLEAK=y, which is doing
similar for stack memory.

Link: https://lore.kernel.org/r/20250717232519.2984886-13-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

diff --git a/kernel/configs/hardening.config b/kernel/configs/hardening.config
index d24c2772d04d7f7444b04084c8764d95735b5b87..64caaf997fc08963a07d979d2a35fb0647acd713 100644 (file)
--- a/kernel/configs/hardening.config
+++ b/kernel/configs/hardening.config
@@ -60,6 +60,9 @@ CONFIG_LIST_HARDENED=y
 # Initialize all heap variables to zero on allocation.
 CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
 
+# Initialize all heap variables to zero on free to reduce stale data lifetime.
+CONFIG_INIT_ON_FREE_DEFAULT_ON=y
+
 # Initialize all stack variables to zero on function entry.
 CONFIG_INIT_STACK_ALL_ZERO=y