Re: [PATCH] arch/riscv: Add support for STACKLEAK gcc plugin

[Dao Lu <daolu@rivosinc.com>]

Thanks Kees.

> stackleak_check_alloca does not exist. Was this maybe from an older
commit log?

Yeah it was from an older version and was later removed, I will take it away
from the commit message in the next version.

Thanks,
Dao


On Wed, Jun 15, 2022 at 10:36 PM Kees Cook <keescook@chromium.org> wrote:
>
> 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@rivosinc.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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