[PATCH] powerpc: Interrupt handler stack randomisation

[Christophe Leroy]

Le 25/10/2022 à 05:38, Rohan McLure a écrit :
> Stack frames used by syscall handlers support random offsets as of
> commit f4a0318f278d (powerpc: add support for syscall stack randomization).
> Implement the same for general interrupt handlers, by applying the
> random stack offset and then updating this offset from within the
> DEFINE_INTERRUPT_HANDLER macros.
> 
> Applying this offset perturbs the layout of interrupt handler stack
> frames, rendering to the kernel stack more difficult to control by means
> of user invoked interrupts.
> 
> Link: https://lists.ozlabs.org/pipermail/linuxppc-dev/2022-May/243238.html
> 
> Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>

Reviewed-by: Christophe Leroy <christophe.leroy at csgroup.eu>


> ---
>   arch/powerpc/include/asm/interrupt.h | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
> index 4745bb9998bd..b7f7beff4e13 100644
> --- a/arch/powerpc/include/asm/interrupt.h
> +++ b/arch/powerpc/include/asm/interrupt.h
> @@ -68,6 +68,7 @@
>   
>   #include <linux/context_tracking.h>
>   #include <linux/hardirq.h>
> +#include <linux/randomize_kstack.h>
>   #include <asm/cputime.h>
>   #include <asm/firmware.h>
>   #include <asm/ftrace.h>
> @@ -448,9 +449,12 @@ interrupt_handler long func(struct pt_regs *regs)			\
>   	long ret;							\
>   									\
>   	__hard_RI_enable();						\
> +	add_random_kstack_offset();					\
>   									\
>   	ret = ____##func (regs);					\
>   									\
> +	choose_random_kstack_offset(mftb());				\
> +									\
>   	return ret;							\
>   }									\
>   NOKPROBE_SYMBOL(func);							\
> @@ -480,9 +484,11 @@ static __always_inline void ____##func(struct pt_regs *regs);		\
>   interrupt_handler void func(struct pt_regs *regs)			\
>   {									\
>   	interrupt_enter_prepare(regs);					\
> +	add_random_kstack_offset();					\
>   									\
>   	____##func (regs);						\
>   									\
> +	choose_random_kstack_offset(mftb());				\
>   	interrupt_exit_prepare(regs);					\
>   }									\
>   NOKPROBE_SYMBOL(func);							\
> @@ -515,9 +521,11 @@ interrupt_handler long func(struct pt_regs *regs)			\
>   	long ret;							\
>   									\
>   	interrupt_enter_prepare(regs);					\
> +	add_random_kstack_offset();					\
>   									\
>   	ret = ____##func (regs);					\
>   									\
> +	choose_random_kstack_offset(mftb());				\
>   	interrupt_exit_prepare(regs);					\
>   									\
>   	return ret;							\
> @@ -548,9 +556,11 @@ static __always_inline void ____##func(struct pt_regs *regs);		\
>   interrupt_handler void func(struct pt_regs *regs)			\
>   {									\
>   	interrupt_async_enter_prepare(regs);				\
> +	add_random_kstack_offset();					\
>   									\
>   	____##func (regs);						\
>   									\
> +	choose_random_kstack_offset(mftb());				\
>   	interrupt_async_exit_prepare(regs);				\
>   }									\
>   NOKPROBE_SYMBOL(func);							\
> @@ -585,9 +595,11 @@ interrupt_handler long func(struct pt_regs *regs)			\
>   	long ret;							\
>   									\
>   	interrupt_nmi_enter_prepare(regs, &state);			\
> +	add_random_kstack_offset();					\
>   									\
>   	ret = ____##func (regs);					\
>   									\
> +	choose_random_kstack_offset(mftb());				\
>   	interrupt_nmi_exit_prepare(regs, &state);			\
>   									\
>   	return ret;							\