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Date: Wed, 10 Apr 2019 09:16:11 -0700
From: Kees Cook <keescook@...omium.org>
To: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: Kees Cook <keescook@...omium.org>,
	Alexander Potapenko <glider@...gle.com>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Sandeep Patil <sspatil@...roid.com>,
	Laura Abbott <labbott@...hat.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Alexander Popov <alpopov@...ecurity.com>,
	Michal Marek <michal.lkml@...kovi.net>,
	Emese Revfy <re.emese@...il.com>,
	James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	kernel-hardening@...ts.openwall.com
Subject: [PATCH 2/3] kbuild: Move stackleak config to Kconfig.hardening

This moves the stackleak plugin options to Kconfig.hardening's memory
initialization menu.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 scripts/gcc-plugins/Kconfig | 51 ---------------------------------
 security/Kconfig.hardening  | 57 +++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 51 deletions(-)

diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
index 01874ef0f883..50cfcf1ed979 100644
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -107,57 +107,6 @@ config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
 	  in structures.  This reduces the performance hit of RANDSTRUCT
 	  at the cost of weakened randomization.
 
-config GCC_PLUGIN_STACKLEAK
-	bool "Erase the kernel stack before returning from syscalls"
-	depends on GCC_PLUGINS
-	depends on HAVE_ARCH_STACKLEAK
-	help
-	  This option makes the kernel erase the kernel stack before
-	  returning from system calls. That reduces the information which
-	  kernel stack leak bugs can reveal and blocks some uninitialized
-	  stack variable attacks.
-
-	  The tradeoff is the performance impact: on a single CPU system kernel
-	  compilation sees a 1% slowdown, other systems and workloads may vary
-	  and you are advised to test this feature on your expected workload
-	  before deploying it.
-
-	  This plugin was ported from grsecurity/PaX. More information at:
-	   * https://grsecurity.net/
-	   * https://pax.grsecurity.net/
-
-config STACKLEAK_TRACK_MIN_SIZE
-	int "Minimum stack frame size of functions tracked by STACKLEAK"
-	default 100
-	range 0 4096
-	depends on GCC_PLUGIN_STACKLEAK
-	help
-	  The STACKLEAK gcc plugin instruments the kernel code for tracking
-	  the lowest border of the kernel stack (and for some other purposes).
-	  It inserts the stackleak_track_stack() call for the functions with
-	  a stack frame size greater than or equal to this parameter.
-	  If unsure, leave the default value 100.
-
-config STACKLEAK_METRICS
-	bool "Show STACKLEAK metrics in the /proc file system"
-	depends on GCC_PLUGIN_STACKLEAK
-	depends on PROC_FS
-	help
-	  If this is set, STACKLEAK metrics for every task are available in
-	  the /proc file system. In particular, /proc/<pid>/stack_depth
-	  shows the maximum kernel stack consumption for the current and
-	  previous syscalls. Although this information is not precise, it
-	  can be useful for estimating the STACKLEAK performance impact for
-	  your workloads.
-
-config STACKLEAK_RUNTIME_DISABLE
-	bool "Allow runtime disabling of kernel stack erasing"
-	depends on GCC_PLUGIN_STACKLEAK
-	help
-	  This option provides 'stack_erasing' sysctl, which can be used in
-	  runtime to control kernel stack erasing for kernels built with
-	  CONFIG_GCC_PLUGIN_STACKLEAK.
-
 config GCC_PLUGIN_ARM_SSP_PER_TASK
 	bool
 	depends on GCC_PLUGINS && ARM
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index 8223a8ab1a12..9942d9869864 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -89,6 +89,63 @@ config GCC_PLUGIN_STRUCTLEAK_VERBOSE
 	  initialized. Since not all existing initializers are detected
 	  by the plugin, this can produce false positive warnings.
 
+config GCC_PLUGIN_STACKLEAK
+	bool "Poison kernel stack before returning from syscalls"
+	depends on GCC_PLUGINS
+	depends on HAVE_ARCH_STACKLEAK
+	help
+	  This option makes the kernel erase the kernel stack before
+	  returning from system calls. This has the effect of leaving
+	  the stack initialized to the poison value, which both reduces
+	  the lifetime of any sensitive stack contents and reduces
+	  potential for uninitialized stack variable exploits or information
+	  exposures (it does not cover functions reaching the same stack
+	  depth as prior functions during the same syscall). This blocks
+	  most uninitialized stack variable attacks, with the performance
+	  impact being driven by the depth of the stack usage, rather than
+	  the function calling complexity.
+
+	  The performance impact on a single CPU system kernel compilation
+	  sees a 1% slowdown, other systems and workloads may vary and you
+	  are advised to test this feature on your expected workload before
+	  deploying it.
+
+	  This plugin was ported from grsecurity/PaX. More information at:
+	   * https://grsecurity.net/
+	   * https://pax.grsecurity.net/
+
+config STACKLEAK_TRACK_MIN_SIZE
+	int "Minimum stack frame size of functions tracked by STACKLEAK"
+	default 100
+	range 0 4096
+	depends on GCC_PLUGIN_STACKLEAK
+	help
+	  The STACKLEAK gcc plugin instruments the kernel code for tracking
+	  the lowest border of the kernel stack (and for some other purposes).
+	  It inserts the stackleak_track_stack() call for the functions with
+	  a stack frame size greater than or equal to this parameter.
+	  If unsure, leave the default value 100.
+
+config STACKLEAK_METRICS
+	bool "Show STACKLEAK metrics in the /proc file system"
+	depends on GCC_PLUGIN_STACKLEAK
+	depends on PROC_FS
+	help
+	  If this is set, STACKLEAK metrics for every task are available in
+	  the /proc file system. In particular, /proc/<pid>/stack_depth
+	  shows the maximum kernel stack consumption for the current and
+	  previous syscalls. Although this information is not precise, it
+	  can be useful for estimating the STACKLEAK performance impact for
+	  your workloads.
+
+config STACKLEAK_RUNTIME_DISABLE
+	bool "Allow runtime disabling of kernel stack erasing"
+	depends on GCC_PLUGIN_STACKLEAK
+	help
+	  This option provides 'stack_erasing' sysctl, which can be used in
+	  runtime to control kernel stack erasing for kernels built with
+	  CONFIG_GCC_PLUGIN_STACKLEAK.
+
 endmenu
 
 endmenu
-- 
2.17.1

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