3 files changed, 69 insertions, 4 deletions

diff --git a/Makefile b/Makefile
index 84fb5cd092d2..5271b9623aa3 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 24e026d83072..80bbb8ccd0d1 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 31bd43b82095..d4f891f56996 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;