Re: [PATCH v1 06/10] asm-generic: Refactor dereference_[kernel]_function_descriptor()

Kees Cook
2021-10-13T07:02:12Z

On Mon, Oct 11, 2021 at 05:25:33PM +0200, Christophe Leroy wrote:
> dereference_function_descriptor() and
> dereference_kernel_function_descriptor() are identical on the
> three architectures implementing them.
>
> Make it common.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/ia64/include/asm/sections.h | 19 -------------------
> arch/parisc/include/asm/sections.h | 9 ---------
> arch/parisc/kernel/process.c | 21 ---------------------
> arch/powerpc/include/asm/sections.h | 23 -----------------------
> include/asm-generic/sections.h | 18 ++++++++++++++++++
> 5 files changed, 18 insertions(+), 72 deletions(-)

A diffstat to love. :)

Reviewed-by: Kees Cook <keescook@chromium.org>

>
> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> index 929b5c535620..d9addaea8339 100644
> --- a/arch/ia64/include/asm/sections.h
> +++ b/arch/ia64/include/asm/sections.h
> @@ -30,23 +30,4 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
> extern char __start_unwind[], __end_unwind[];
> extern char __start_ivt_text[], __end_ivt_text[];
>
> -#undef dereference_function_descriptor
> -static inline void *dereference_function_descriptor(void *ptr)
> -{
> - struct fdesc *desc = ptr;
> - void *p;
> -
> - if (!get_kernel_nofault(p, (void *)&desc->addr))
> - ptr = p;
> - return ptr;
> -}
> -
> -#undef dereference_kernel_function_descriptor
> -static inline void *dereference_kernel_function_descriptor(void *ptr)
> -{
> - if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
> - return ptr;
> - return dereference_function_descriptor(ptr);
> -}
> -
> #endif /* _ASM_IA64_SECTIONS_H */
> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
> index 329e80f7af0a..b041fb32a300 100644
> --- a/arch/parisc/include/asm/sections.h
> +++ b/arch/parisc/include/asm/sections.h
> @@ -12,13 +12,4 @@ typedef Elf64_Fdesc funct_descr_t;
>
> extern char __alt_instructions[], __alt_instructions_end[];
>
> -#ifdef CONFIG_64BIT
> -
> -#undef dereference_function_descriptor
> -void *dereference_function_descriptor(void *);
> -
> -#undef dereference_kernel_function_descriptor
> -void *dereference_kernel_function_descriptor(void *);
> -#endif
> -
> #endif
> diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
> index 38ec4ae81239..7382576b52a8 100644
> --- a/arch/parisc/kernel/process.c
> +++ b/arch/parisc/kernel/process.c
> @@ -266,27 +266,6 @@ get_wchan(struct task_struct *p)
> return 0;
> }
>
> -#ifdef CONFIG_64BIT
> -void *dereference_function_descriptor(void *ptr)
> -{
> - Elf64_Fdesc *desc = ptr;
> - void *p;
> -
> - if (!get_kernel_nofault(p, (void *)&desc->addr))
> - ptr = p;
> - return ptr;
> -}
> -
> -void *dereference_kernel_function_descriptor(void *ptr)
> -{
> - if (ptr < (void *)__start_opd ||
> - ptr >= (void *)__end_opd)
> - return ptr;
> -
> - return dereference_function_descriptor(ptr);
> -}
> -#endif
> -
> static inline unsigned long brk_rnd(void)
> {
> return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index d0d5287fa568..8f8e95f234e2 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -72,29 +72,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
> (unsigned long)_stext < end;
> }
>
> -#ifdef PPC64_ELF_ABI_v1
> -
> -#undef dereference_function_descriptor
> -static inline void *dereference_function_descriptor(void *ptr)
> -{
> - struct ppc64_opd_entry *desc = ptr;
> - void *p;
> -
> - if (!get_kernel_nofault(p, (void *)&desc->addr))
> - ptr = p;
> - return ptr;
> -}
> -
> -#undef dereference_kernel_function_descriptor
> -static inline void *dereference_kernel_function_descriptor(void *ptr)
> -{
> - if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
> - return ptr;
> -
> - return dereference_function_descriptor(ptr);
> -}
> -#endif /* PPC64_ELF_ABI_v1 */
> -
> #endif
>
> #endif /* __KERNEL__ */
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index 436412d94054..5baaf9d7c671 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -60,6 +60,24 @@ extern __visible const void __nosave_begin, __nosave_end;
>
> /* Function descriptor handling (if any). Override in asm/sections.h */
> #ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
> +static inline void *dereference_function_descriptor(void *ptr)
> +{
> + funct_descr_t *desc = ptr;
> + void *p;
> +
> + if (!get_kernel_nofault(p, (void *)&desc->addr))
> + ptr = p;
> + return ptr;
> +}
> +
> +static inline void *dereference_kernel_function_descriptor(void *ptr)
> +{
> + if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
> + return ptr;
> +
> + return dereference_function_descriptor(ptr);
> +}
> +
> #else
> #define dereference_function_descriptor(p) ((void *)(p))
> #define dereference_kernel_function_descriptor(p) ((void *)(p))
> --
> 2.31.1
>

--
Kees Cook