linux-kernel - Re: [PATCH] carl9170: Replace zero-length array of trailing structs with flex-array

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Message-ID: <0500eccc-412b-40f3-e19b-251f383ff903@gmail.com>
Date:   Fri, 18 Nov 2022 23:54:55 +0100
From:   Christian Lamparter <chunkeey@...il.com>
To:     Kees Cook <keescook@...omium.org>,
        Christian Lamparter <chunkeey@...glemail.com>
Cc:     Kalle Valo <kvalo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] carl9170: Replace zero-length array of trailing structs
 with flex-array

On 11/18/22 22:11, Kees Cook wrote:
> Zero-length arrays are deprecated[1] and are being replaced with
> flexible array members in support of the ongoing efforts to tighten the
> FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
> with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.
> 
> Replace zero-length array with flexible-array member.
> 
> This results in no differences in binary output.
> 
> [1] https://github.com/KSPP/linux/issues/78
> 
> Cc: Christian Lamparter <chunkeey@...glemail.com>
> Cc: Kalle Valo <kvalo@...nel.org>
> 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: "Gustavo A. R. Silva" <gustavoars@...nel.org>
> Cc: linux-wireless@...r.kernel.org
> Cc: netdev@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
Acked-by: Christian Lamparter <chunkeey@...il.com>

> ---
>   drivers/net/wireless/ath/carl9170/fwcmd.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/carl9170/fwcmd.h b/drivers/net/wireless/ath/carl9170/fwcmd.h
> index 4a500095555c..ff4b3b50250c 100644
> --- a/drivers/net/wireless/ath/carl9170/fwcmd.h
> +++ b/drivers/net/wireless/ath/carl9170/fwcmd.h
> @@ -118,10 +118,10 @@ struct carl9170_reg_list {
>   } __packed;
>   
>   struct carl9170_write_reg {
> -	struct {
> +	DECLARE_FLEX_ARRAY(struct {
>   		__le32		addr;
>   		__le32		val;
> -	} regs[0] __packed;
> +	} __packed, regs);
>   } __packed;
>   
>   struct carl9170_write_reg_byte {