linux-kernel - Re: [PATCH] hinic: Replace memcpy() with direct assignment

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Message-ID: <YqtmIIAOH7uRNAZ5@dev-arch.thelio-3990X>
Date:   Thu, 16 Jun 2022 10:19:28 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Leon Romanovsky <leon@...nel.org>,
        Jiri Pirko <jiri@...dia.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Simon Horman <simon.horman@...igine.com>,
        netdev@...r.kernel.org, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] hinic: Replace memcpy() with direct assignment

On Wed, Jun 15, 2022 at 10:23:12PM -0700, Kees Cook wrote:
> Under CONFIG_FORTIFY_SOURCE=y and CONFIG_UBSAN_BOUNDS=y, Clang is bugged
> here for calculating the size of the destination buffer (0x10 instead of
> 0x14). This copy is a fixed size (sizeof(struct fw_section_info_st)), with
> the source and dest being struct fw_section_info_st, so the memcpy should
> be safe, assuming the index is within bounds, which is UBSAN_BOUNDS's
> responsibility to figure out.
> 
> Avoid the whole thing and just do a direct assignment. This results in
> no change to the executable code.
> 
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: Nathan Chancellor <nathan@...nel.org>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Cc: Tom Rix <trix@...hat.com>
> Cc: Leon Romanovsky <leon@...nel.org>
> Cc: Jiri Pirko <jiri@...dia.com>
> Cc: Vladimir Oltean <olteanv@...il.com>
> Cc: Simon Horman <simon.horman@...igine.com>
> Cc: netdev@...r.kernel.org
> Cc: llvm@...ts.linux.dev
> Link: https://github.com/ClangBuiltLinux/linux/issues/1592
> Signed-off-by: Kees Cook <keescook@...omium.org>

Tested-by: Nathan Chancellor <nathan@...nel.org> # build

> ---
>  drivers/net/ethernet/huawei/hinic/hinic_devlink.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/huawei/hinic/hinic_devlink.c b/drivers/net/ethernet/huawei/hinic/hinic_devlink.c
> index 60ae8bfc5f69..1749d26f4bef 100644
> --- a/drivers/net/ethernet/huawei/hinic/hinic_devlink.c
> +++ b/drivers/net/ethernet/huawei/hinic/hinic_devlink.c
> @@ -43,9 +43,7 @@ static bool check_image_valid(struct hinic_devlink_priv *priv, const u8 *buf,
>  
>  	for (i = 0; i < fw_image->fw_info.fw_section_cnt; i++) {
>  		len += fw_image->fw_section_info[i].fw_section_len;
> -		memcpy(&host_image->image_section_info[i],
> -		       &fw_image->fw_section_info[i],
> -		       sizeof(struct fw_section_info_st));
> +		host_image->image_section_info[i] = fw_image->fw_section_info[i];
>  	}
>  
>  	if (len != fw_image->fw_len ||
> -- 
> 2.32.0
>