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Date: Mon, 20 Jan 2014 12:47:24 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] Stackprotector updates for v3.14
Linus,
Please pull the latest core-stackprotector-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-stackprotector-for-linus
# HEAD: 8779657d29c0ebcc0c94ede4df2f497baf1b563f stackprotector: Introduce CONFIG_CC_STACKPROTECTOR_STRONG
This tree adds a CONFIG_CC_STACKPROTECTOR_STRONG=y, a new, stronger
stack canary checking method supported by the newest GCC versions (4.9
and later).
Here's the 'intensity comparison' between the various protection
modes:
- defconfig
11430641 kernel text size
36110 function bodies
- defconfig + CONFIG_CC_STACKPROTECTOR_REGULAR
11468490 kernel text size (+0.33%)
1015 of 36110 functions are stack-protected (2.81%)
- defconfig + CONFIG_CC_STACKPROTECTOR_STRONG via this patch
11692790 kernel text size (+2.24%)
7401 of 36110 functions are stack-protected (20.5%)
the strong model comes with non-trivial costs, which is why we
preserved the 'regular' and 'none' models as well.
Thanks,
Ingo
------------------>
Kees Cook (2):
stackprotector: Unify the HAVE_CC_STACKPROTECTOR logic between architectures
stackprotector: Introduce CONFIG_CC_STACKPROTECTOR_STRONG
Makefile | 20 ++++++++++--
arch/Kconfig | 67 +++++++++++++++++++++++++++++++++++++++++
arch/arm/Kconfig | 13 +-------
arch/arm/Makefile | 4 ---
arch/arm/boot/compressed/misc.c | 14 +++++++++
arch/mips/Kconfig | 14 +--------
arch/mips/Makefile | 4 ---
arch/sh/Kconfig | 15 +--------
arch/sh/Makefile | 4 ---
arch/x86/Kconfig | 17 +----------
arch/x86/Makefile | 8 ++---
11 files changed, 105 insertions(+), 75 deletions(-)
diff --git a/Makefile b/Makefile
index 858a147..5271b96 100644
--- a/Makefile
+++ b/Makefile
@@ -595,10 +595,24 @@ ifneq ($(CONFIG_FRAME_WARN),0)
KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
-# Force gcc to behave correct even for buggy distributions
-ifndef CONFIG_CC_STACKPROTECTOR
-KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
+# Handle stack protector mode.
+ifdef CONFIG_CC_STACKPROTECTOR_REGULAR
+ stackp-flag := -fstack-protector
+ ifeq ($(call cc-option, $(stackp-flag)),)
+ $(warning Cannot use CONFIG_CC_STACKPROTECTOR: \
+ -fstack-protector not supported by compiler))
+ endif
+else ifdef CONFIG_CC_STACKPROTECTOR_STRONG
+ stackp-flag := -fstack-protector-strong
+ ifeq ($(call cc-option, $(stackp-flag)),)
+ $(warning Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: \
+ -fstack-protector-strong not supported by compiler)
+ endif
+else
+ # Force off for distro compilers that enable stack protector by default.
+ stackp-flag := $(call cc-option, -fno-stack-protector)
endif
+KBUILD_CFLAGS += $(stackp-flag)
# This warning generated too much noise in a regular build.
# Use make W=1 to enable this warning (see scripts/Makefile.build)
diff --git a/arch/Kconfig b/arch/Kconfig
index f1cf895..80bbb8c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -336,6 +336,73 @@ config SECCOMP_FILTER
See Documentation/prctl/seccomp_filter.txt for details.
+config HAVE_CC_STACKPROTECTOR
+ bool
+ help
+ An arch should select this symbol if:
+ - its compiler supports the -fstack-protector option
+ - it has implemented a stack canary (e.g. __stack_chk_guard)
+
+config CC_STACKPROTECTOR
+ def_bool n
+ help
+ Set when a stack-protector mode is enabled, so that the build
+ can enable kernel-side support for the GCC feature.
+
+choice
+ prompt "Stack Protector buffer overflow detection"
+ depends on HAVE_CC_STACKPROTECTOR
+ default CC_STACKPROTECTOR_NONE
+ help
+ This option turns on the "stack-protector" GCC feature. This
+ feature puts, at the beginning of functions, a canary value on
+ the stack just before the return address, and validates
+ the value just before actually returning. Stack based buffer
+ overflows (that need to overwrite this return address) now also
+ overwrite the canary, which gets detected and the attack is then
+ neutralized via a kernel panic.
+
+config CC_STACKPROTECTOR_NONE
+ bool "None"
+ help
+ Disable "stack-protector" GCC feature.
+
+config CC_STACKPROTECTOR_REGULAR
+ bool "Regular"
+ select CC_STACKPROTECTOR
+ help
+ Functions will have the stack-protector canary logic added if they
+ have an 8-byte or larger character array on the stack.
+
+ This feature requires gcc version 4.2 or above, or a distribution
+ gcc with the feature backported ("-fstack-protector").
+
+ On an x86 "defconfig" build, this feature adds canary checks to
+ about 3% of all kernel functions, which increases kernel code size
+ by about 0.3%.
+
+config CC_STACKPROTECTOR_STRONG
+ bool "Strong"
+ select CC_STACKPROTECTOR
+ help
+ Functions will have the stack-protector canary logic added in any
+ of the following conditions:
+
+ - local variable's address used as part of the right hand side of an
+ assignment or function argument
+ - local variable is an array (or union containing an array),
+ regardless of array type or length
+ - uses register local variables
+
+ This feature requires gcc version 4.9 or above, or a distribution
+ gcc with the feature backported ("-fstack-protector-strong").
+
+ On an x86 "defconfig" build, this feature adds canary checks to
+ about 20% of all kernel functions, which increases the kernel code
+ size by about 2%.
+
+endchoice
+
config HAVE_CONTEXT_TRACKING
bool
help
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c1f1a7e..9c909fc 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -30,6 +30,7 @@ config ARM
select HAVE_BPF_JIT
select HAVE_CONTEXT_TRACKING
select HAVE_C_RECORDMCOUNT
+ select HAVE_CC_STACKPROTECTOR
select HAVE_DEBUG_KMEMLEAK
select HAVE_DMA_API_DEBUG
select HAVE_DMA_ATTRS
@@ -1856,18 +1857,6 @@ config SECCOMP
and the task is only allowed to execute a few safe syscalls
defined by each seccomp mode.
-config CC_STACKPROTECTOR
- bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
- help
- This option turns on the -fstack-protector GCC feature. This
- feature puts, at the beginning of functions, a canary value on
- the stack just before the return address, and validates
- the value just before actually returning. Stack based buffer
- overflows (that need to overwrite this return address) now also
- overwrite the canary, which gets detected and the attack is then
- neutralized via a kernel panic.
- This feature requires gcc version 4.2 or above.
-
config SWIOTLB
def_bool y
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index c99b108..55b4255 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -40,10 +40,6 @@ ifeq ($(CONFIG_FRAME_POINTER),y)
KBUILD_CFLAGS +=-fno-omit-frame-pointer -mapcs -mno-sched-prolog
endif
-ifeq ($(CONFIG_CC_STACKPROTECTOR),y)
-KBUILD_CFLAGS +=-fstack-protector
-endif
-
ifeq ($(CONFIG_CPU_BIG_ENDIAN),y)
KBUILD_CPPFLAGS += -mbig-endian
AS += -EB
diff --git a/arch/arm/boot/compressed/misc.c b/arch/arm/boot/compressed/misc.c
index 31bd43b..d4f891f 100644
--- a/arch/arm/boot/compressed/misc.c
+++ b/arch/arm/boot/compressed/misc.c
@@ -127,6 +127,18 @@ asmlinkage void __div0(void)
error("Attempting division by 0!");
}
+unsigned long __stack_chk_guard;
+
+void __stack_chk_guard_setup(void)
+{
+ __stack_chk_guard = 0x000a0dff;
+}
+
+void __stack_chk_fail(void)
+{
+ error("stack-protector: Kernel stack is corrupted\n");
+}
+
extern int do_decompress(u8 *input, int len, u8 *output, void (*error)(char *x));
@@ -137,6 +149,8 @@ decompress_kernel(unsigned long output_start, unsigned long free_mem_ptr_p,
{
int ret;
+ __stack_chk_guard_setup();
+
output_data = (unsigned char *)output_start;
free_mem_ptr = free_mem_ptr_p;
free_mem_end_ptr = free_mem_ptr_end_p;
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 650de39..c93d92b 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -47,6 +47,7 @@ config MIPS
select MODULES_USE_ELF_RELA if MODULES && 64BIT
select CLONE_BACKWARDS
select HAVE_DEBUG_STACKOVERFLOW
+ select HAVE_CC_STACKPROTECTOR
menu "Machine selection"
@@ -2322,19 +2323,6 @@ config SECCOMP
If unsure, say Y. Only embedded should say N here.
-config CC_STACKPROTECTOR
- bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
- help
- This option turns on the -fstack-protector GCC feature. This
- feature puts, at the beginning of functions, a canary value on
- the stack just before the return address, and validates
- the value just before actually returning. Stack based buffer
- overflows (that need to overwrite this return address) now also
- overwrite the canary, which gets detected and the attack is then
- neutralized via a kernel panic.
-
- This feature requires gcc version 4.2 or above.
-
config USE_OF
bool
select OF
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index de300b9..efe50787 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -232,10 +232,6 @@ bootvars-y = VMLINUX_LOAD_ADDRESS=$(load-y) \
LDFLAGS += -m $(ld-emul)
-ifdef CONFIG_CC_STACKPROTECTOR
- KBUILD_CFLAGS += -fstack-protector
-endif
-
ifdef CONFIG_MIPS
CHECKFLAGS += $(shell $(CC) $(KBUILD_CFLAGS) -dM -E -x c /dev/null | \
egrep -vw '__GNUC_(|MINOR_|PATCHLEVEL_)_' | \
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 9b0979f..ce29831 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -66,6 +66,7 @@ config SUPERH32
select PERF_EVENTS
select ARCH_HIBERNATION_POSSIBLE if MMU
select SPARSE_IRQ
+ select HAVE_CC_STACKPROTECTOR
config SUPERH64
def_bool ARCH = "sh64"
@@ -695,20 +696,6 @@ config SECCOMP
If unsure, say N.
-config CC_STACKPROTECTOR
- bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
- depends on SUPERH32
- help
- This option turns on the -fstack-protector GCC feature. This
- feature puts, at the beginning of functions, a canary value on
- the stack just before the return address, and validates
- the value just before actually returning. Stack based buffer
- overflows (that need to overwrite this return address) now also
- overwrite the canary, which gets detected and the attack is then
- neutralized via a kernel panic.
-
- This feature requires gcc version 4.2 or above.
-
config SMP
bool "Symmetric multi-processing support"
depends on SYS_SUPPORTS_SMP
diff --git a/arch/sh/Makefile b/arch/sh/Makefile
index aed701c..d4d16e4 100644
--- a/arch/sh/Makefile
+++ b/arch/sh/Makefile
@@ -199,10 +199,6 @@ ifeq ($(CONFIG_DWARF_UNWINDER),y)
KBUILD_CFLAGS += -fasynchronous-unwind-tables
endif
-ifeq ($(CONFIG_CC_STACKPROTECTOR),y)
- KBUILD_CFLAGS += -fstack-protector
-endif
-
libs-$(CONFIG_SUPERH32) := arch/sh/lib/ $(libs-y)
libs-$(CONFIG_SUPERH64) := arch/sh/lib64/ $(libs-y)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0952ecd..838e7c3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -125,6 +125,7 @@ config X86
select RTC_LIB
select HAVE_DEBUG_STACKOVERFLOW
select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
+ select HAVE_CC_STACKPROTECTOR
config INSTRUCTION_DECODER
def_bool y
@@ -1617,22 +1618,6 @@ config SECCOMP
If unsure, say Y. Only embedded should say N here.
-config CC_STACKPROTECTOR
- bool "Enable -fstack-protector buffer overflow detection"
- ---help---
- This option turns on the -fstack-protector GCC feature. This
- feature puts, at the beginning of functions, a canary value on
- the stack just before the return address, and validates
- the value just before actually returning. Stack based buffer
- overflows (that need to overwrite this return address) now also
- overwrite the canary, which gets detected and the attack is then
- neutralized via a kernel panic.
-
- This feature requires gcc version 4.2 or above, or a distribution
- gcc with the feature backported. Older versions are automatically
- detected and for those versions, this configuration option is
- ignored. (and a warning is printed during bootup)
-
source kernel/Kconfig.hz
config KEXEC
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 57d0215..13b22e0 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -89,13 +89,11 @@ else
KBUILD_CFLAGS += -maccumulate-outgoing-args
endif
+# Make sure compiler does not have buggy stack-protector support.
ifdef CONFIG_CC_STACKPROTECTOR
cc_has_sp := $(srctree)/scripts/gcc-x86_$(BITS)-has-stack-protector.sh
- ifeq ($(shell $(CONFIG_SHELL) $(cc_has_sp) $(CC) $(KBUILD_CPPFLAGS) $(biarch)),y)
- stackp-y := -fstack-protector
- KBUILD_CFLAGS += $(stackp-y)
- else
- $(warning stack protector enabled but no compiler support)
+ ifneq ($(shell $(CONFIG_SHELL) $(cc_has_sp) $(CC) $(KBUILD_CPPFLAGS) $(biarch)),y)
+ $(warning stack-protector enabled but compiler support broken)
endif
endif
--
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