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-rw-r--r--Makefile8
-rw-r--r--arch/Kconfig51
-rw-r--r--arch/arm/boot/compressed/misc.c14
3 files changed, 69 insertions, 4 deletions
diff --git a/Makefile b/Makefile
index 84fb5cd092d..5271b9623aa 100644
--- a/Makefile
+++ b/Makefile
@@ -596,12 +596,18 @@ KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
# Handle stack protector mode.
-ifdef CONFIG_CC_STACKPROTECTOR
+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)
diff --git a/arch/Kconfig b/arch/Kconfig
index 24e026d8307..80bbb8ccd0d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -344,10 +344,17 @@ config HAVE_CC_STACKPROTECTOR
- it has implemented a stack canary (e.g. __stack_chk_guard)
config CC_STACKPROTECTOR
- bool "Enable -fstack-protector buffer overflow detection"
+ 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 -fstack-protector GCC feature. This
+ 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
@@ -355,8 +362,46 @@ config CC_STACKPROTECTOR
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.
+ 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
diff --git a/arch/arm/boot/compressed/misc.c b/arch/arm/boot/compressed/misc.c
index 31bd43b8209..d4f891f5699 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;