linux-kernel - Re: [PATCH v3 8/8] percpu: Add __alloc_size attributes for better bounds checking

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Date:   Fri, 1 Oct 2021 10:15:52 -0400
From:   Dennis Zhou <dennis@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Andy Whitcroft <apw@...onical.com>,
        David Rientjes <rientjes@...gle.com>,
        Dwaipayan Ray <dwaipayanray1@...il.com>,
        Joe Perches <joe@...ches.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Daniel Micay <danielmicay@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        clang-built-linux@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3 8/8] percpu: Add __alloc_size attributes for better
 bounds checking

Hello,

On Thu, Sep 30, 2021 at 03:27:04PM -0700, Kees Cook wrote:
> As already done in GrapheneOS, add the __alloc_size attribute for
> appropriate percpu allocator interfaces, to provide additional hinting for
> better bounds checking, assisting CONFIG_FORTIFY_SOURCE and other compiler
> optimizations.
> 
> Note that due to the implementation of the percpu API, this is unlikely
> to ever actually provide compile-time checking beyond very simple non-SMP
> builds. But, since they are technically allocators, mark them as such.
> 
> Cc: Dennis Zhou <dennis@...nel.org>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Andy Whitcroft <apw@...onical.com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Dwaipayan Ray <dwaipayanray1@...il.com>
> Cc: Joe Perches <joe@...ches.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: Lukas Bulwahn <lukas.bulwahn@...il.com>
> Cc: Miguel Ojeda <ojeda@...nel.org>
> Cc: Nathan Chancellor <nathan@...nel.org>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Cc: Pekka Enberg <penberg@...nel.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Co-developed-by: Daniel Micay <danielmicay@...il.com>
> Signed-off-by: Daniel Micay <danielmicay@...il.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>

Thanks for updating the commit log.

Acked-by: Dennis Zhou <dennis@...nel.org>

Thanks,
Dennis

> ---
>  include/linux/percpu.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/percpu.h b/include/linux/percpu.h
> index 5e76af742c80..98a9371133f8 100644
> --- a/include/linux/percpu.h
> +++ b/include/linux/percpu.h
> @@ -123,7 +123,7 @@ extern int __init pcpu_page_first_chunk(size_t reserved_size,
>  				pcpu_fc_populate_pte_fn_t populate_pte_fn);
>  #endif
>  
> -extern void __percpu *__alloc_reserved_percpu(size_t size, size_t align);
> +extern void __percpu *__alloc_reserved_percpu(size_t size, size_t align) __alloc_size(1);
>  extern bool __is_kernel_percpu_address(unsigned long addr, unsigned long *can_addr);
>  extern bool is_kernel_percpu_address(unsigned long addr);
>  
> @@ -131,8 +131,8 @@ extern bool is_kernel_percpu_address(unsigned long addr);
>  extern void __init setup_per_cpu_areas(void);
>  #endif
>  
> -extern void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp);
> -extern void __percpu *__alloc_percpu(size_t size, size_t align);
> +extern void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp) __alloc_size(1);
> +extern void __percpu *__alloc_percpu(size_t size, size_t align) __alloc_size(1);
>  extern void free_percpu(void __percpu *__pdata);
>  extern phys_addr_t per_cpu_ptr_to_phys(void *addr);
>  
> -- 
> 2.30.2
>