Re: [PATCH v2 2/2] powerpc/32: add stack protector support
From: Segher Boessenkool <hidden>
Date: 2018-09-19 13:27:40
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On Wed, Sep 19, 2018 at 11:14:45AM +0000, Christophe Leroy wrote:
quoted hunk ↗ jump to hunk
--- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile@@ -112,6 +112,10 @@ KBUILD_LDFLAGS += -m elf$(BITS)$(LDEMULATION) KBUILD_ARFLAGS += --target=elf$(BITS)-$(GNUTARGET) endif +cflags-$(CONFIG_STACKPROTECTOR) += -mstack-protector-guard=tls +cflags-$(CONFIG_STACKPROTECTOR) += -mstack-protector-guard-reg=r2 +cflags-$(CONFIG_STACKPROTECTOR) += -mstack-protector-guard-offset=4
This last line is only correct if !CONFIG_THREAD_INFO_IN_TASK; is that always true? Add an assert somewhere maybe?
+ /* + * The stack_canary must be located at the offset given to + * -mstack-protector-guard-offset in the Makefile + */ + BUILD_BUG_ON(offsetof(struct task_struct, stack_canary) != sizeof(long));
Well this will help :-) It looks like it will be easy to enable on 64 bit as well.
+ /* Try to get a semi random initial value. */ + get_random_bytes(&canary, sizeof(canary)); + canary ^= mftb(); + canary ^= LINUX_VERSION_CODE;
These last two lines are useless (or worse, they may give people the idea that they are not!) You should use wait_for_random_bytes I think. Segher