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

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Message-ID: <e077bafc-17bf-37de-868a-3ab32f91769d@embeddedor.com>
Date:   Thu, 16 Jun 2022 12:43:40 +0200
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Kees Cook <keescook@...omium.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        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 6/16/22 07:23, 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.

Also, there is a sanity check just before the for() loop:

  38         if (fw_image->fw_info.fw_section_cnt > MAX_FW_TYPE_NUM) {
  39                 dev_err(&priv->hwdev->hwif->pdev->dev, "Wrong fw_type_num read from file, fw_type_num: 0x%x\n    ",
  40                         fw_image->fw_info.fw_section_cnt);
  41                 return false;
  42         }

so, this should be fine.

> 
> 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>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks
--
Gustavo

> ---
>   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 ||