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Message-ID: <202206152234.DE7FC51F9@keescook>
Date: Wed, 15 Jun 2022 22:36:54 -0700
From: Kees Cook <keescook@...omium.org>
To: Dao Lu <daolu@...osinc.com>
Cc: linux-kernel@...r.kernel.org,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Ard Biesheuvel <ardb@...nel.org>, Guo Ren <guoren@...nel.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Arnd Bergmann <arnd@...db.de>,
Tong Tiangen <tongtiangen@...wei.com>,
Mark Rutland <mark.rutland@....com>,
Changbin Du <changbin.du@...el.com>,
Vincent Chen <vincent.chen@...ive.com>,
"open list:RISC-V ARCHITECTURE" <linux-riscv@...ts.infradead.org>,
"open list:EXTENSIBLE FIRMWARE INTERFACE (EFI)"
<linux-efi@...r.kernel.org>
Subject: Re: [PATCH] arch/riscv: Add support for STACKLEAK gcc plugin
On Wed, Jun 15, 2022 at 02:38:29PM -0700, Dao Lu wrote:
> This adds support for STACKLEAK gcc plugin to ricv by implementing
typo: riscv
> stackleak_check_alloca, based heavily on the arm64 version, and adding
stackleak_check_alloca does not exist. Was this maybe from an older
commit log?
> the two helpers used by the stackleak common code:
> current_top_of_stack() and on_thread_stack(). This also adds the missing
> helper functions for riscv, on_stack() and on_task_stack().
> Additionally, this disables the plugin for EFI stub code for riscv.
I can't speak to the arch-specific bits here, but if this passes the
current LKDTM tests, then that should be a good indication that it's
working. :)
>
> Signed-off-by: Dao Lu <daolu@...osinc.com>
> ---
> arch/riscv/Kconfig | 1 +
> arch/riscv/include/asm/processor.h | 18 ++++++++++++++++++
> arch/riscv/include/asm/stacktrace.h | 27 +++++++++++++++++++++++++++
> arch/riscv/kernel/entry.S | 3 +++
> drivers/firmware/efi/libstub/Makefile | 2 +-
> 5 files changed, 50 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index c22f58155948..22aa146acd25 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -80,6 +80,7 @@ config RISCV
> select HAVE_ARCH_MMAP_RND_BITS if MMU
> select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
> select HAVE_ARCH_SECCOMP_FILTER
> + select HAVE_ARCH_STACKLEAK
> select HAVE_ARCH_TRACEHOOK
> select HAVE_ARCH_TRANSPARENT_HUGEPAGE if 64BIT && MMU
> select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
> diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> index 21c8072dce17..3a7505ab7f58 100644
> --- a/arch/riscv/include/asm/processor.h
> +++ b/arch/riscv/include/asm/processor.h
> @@ -85,6 +85,24 @@ int riscv_of_parent_hartid(struct device_node *node);
> extern void riscv_fill_hwcap(void);
> extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
>
> +/*
> + * For CONFIG_GCC_PLUGIN_STACKLEAK
> + *
> + * These need to be macros because otherwise we get stuck in a nightmare
> + * of header definitions for the use of task_stack_page.
> + */
> +
> +struct stack_info {
> + unsigned long low;
> + unsigned long high;
> +};
> +
> +/*
> + * The top of the current task's task stack
> + */
> +#define current_top_of_stack() ((unsigned long)current->stack + THREAD_SIZE)
> +#define on_thread_stack() (on_task_stack(current, current_stack_pointer, 1, NULL))
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* _ASM_RISCV_PROCESSOR_H */
> diff --git a/arch/riscv/include/asm/stacktrace.h b/arch/riscv/include/asm/stacktrace.h
> index 3450c1912afd..afb66b677b6a 100644
> --- a/arch/riscv/include/asm/stacktrace.h
> +++ b/arch/riscv/include/asm/stacktrace.h
> @@ -16,4 +16,31 @@ extern void notrace walk_stackframe(struct task_struct *task, struct pt_regs *re
> extern void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
> const char *loglvl);
>
> +static inline bool on_stack(unsigned long sp, unsigned long size,
> + unsigned long low, unsigned long high,
> + struct stack_info *info)
> +{
> + if (!low)
> + return false;
> +
> + if (sp < low || sp + size < sp || sp + size > high)
> + return false;
> +
> + if (info) {
> + info->low = low;
> + info->high = high;
> + }
> + return true;
> +}
> +
> +static inline bool on_task_stack(const struct task_struct *tsk,
> + unsigned long sp, unsigned long size,
> + struct stack_info *info)
> +{
> + unsigned long low = (unsigned long)task_stack_page(tsk);
> + unsigned long high = low + THREAD_SIZE;
> +
> + return on_stack(sp, size, low, high, info);
> +}
> +
> #endif /* _ASM_RISCV_STACKTRACE_H */
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 2e5b88ca11ce..65d441cb560f 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -264,6 +264,9 @@ ret_from_exception:
> bnez s0, resume_kernel
>
> resume_userspace:
> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
> + call stackleak_erase
> +#endif
> /* Interrupts must be disabled here so flags are checked atomically */
> REG_L s0, TASK_TI_FLAGS(tp) /* current_thread_info->flags */
> andi s1, s0, _TIF_WORK_MASK
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index d0537573501e..5e1fc4f82883 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -25,7 +25,7 @@ cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
> -fno-builtin -fpic \
> $(call cc-option,-mno-single-pic-base)
> cflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
> - -fpic
> + -fpic $(DISABLE_STACKLEAK_PLUGIN)
>
> cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt
>
> --
> 2.25.1
>
--
Kees Cook
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