linux-kernel - [PATCH 8/8] configs/hardening: Enable CONFIG_INIT_ON_FREE_DEFAULT

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Message-Id: <20250507181615.1947159-8-kees@kernel.org>
Date: Wed,  7 May 2025 11:16:14 -0700
From: Kees Cook <kees@...nel.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: Kees Cook <kees@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-hardening@...r.kernel.org,
	Christoph Hellwig <hch@....de>,
	Marco Elver <elver@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	linux-kernel@...r.kernel.org,
	x86@...nel.org,
	kasan-dev@...glegroups.com,
	linux-doc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev,
	linux-riscv@...ts.infradead.org,
	linux-s390@...r.kernel.org,
	linux-efi@...r.kernel.org,
	linux-kbuild@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	sparclinux@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH 8/8] 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.

Signed-off-by: Kees Cook <kees@...nel.org>
---
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: <linux-hardening@...r.kernel.org>
---
 kernel/configs/hardening.config | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/configs/hardening.config b/kernel/configs/hardening.config
index 3da00926b4eb..7d92a740e490 100644
--- 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
 
-- 
2.34.1