linux-kernel - [PATCH] security: Restrict CONFIG_ZERO_CALL_USED

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Message-Id: <20221214232602.4118147-1-nathan@kernel.org>
Date:   Wed, 14 Dec 2022 16:26:03 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Tom Rix <trix@...hat.com>, linux-hardening@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        patches@...ts.linux.dev, Nathan Chancellor <nathan@...nel.org>,
        stable@...r.kernel.org
Subject: [PATCH] security: Restrict CONFIG_ZERO_CALL_USED_REGS to gcc or clang > 15.0.6

A bad bug in clang's implementation of -fzero-call-used-regs can result
in NULL pointer dereferences (see the links above the check for more
information). Restrict CONFIG_CC_HAS_ZERO_CALL_USED_REGS to either a
supported GCC version or a clang newer than 15.0.6, which will catch
both a theoretical 15.0.7 and the upcoming 16.0.0, which will both have
the bug fixed.

Cc: stable@...r.kernel.org # v5.15+
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 security/Kconfig.hardening | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index d766b7d0ffd1..53baa95cb644 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -257,6 +257,9 @@ config INIT_ON_FREE_DEFAULT_ON
 
 config CC_HAS_ZERO_CALL_USED_REGS
 	def_bool $(cc-option,-fzero-call-used-regs=used-gpr)
+	# https://github.com/ClangBuiltLinux/linux/issues/1766
+	# https://github.com/llvm/llvm-project/issues/59242
+	depends on !CC_IS_CLANG || CLANG_VERSION > 150006
 
 config ZERO_CALL_USED_REGS
 	bool "Enable register zeroing on function exit"

base-commit: 830b3c68c1fb1e9176028d02ef86f3cf76aa2476
-- 
2.39.0