netdev - Re: [PATCH] [v2] net: asix: fix fortify warning

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Date: Tue, 12 Dec 2023 10:33:04 +0100
From: Lukasz Stelmach <l.stelmach@...sung.com>
To: Dmitry Antipov <dmantipov@...dex.ru>
Cc: Jakub Kicinski <kuba@...nel.org>,  netdev@...r.kernel.org
Subject: Re: [PATCH] [v2] net: asix: fix fortify warning

It was <2023-12-11 pon 12:05>, when Dmitry Antipov wrote:
> When compiling with gcc version 14.0.0 20231129 (experimental) and
> CONFIG_FORTIFY_SOURCE=y, I've noticed the following warning:
>
> ...
> In function 'fortify_memcpy_chk',
>     inlined from 'ax88796c_tx_fixup' at drivers/net/ethernet/asix/ax88796c_main.c:287:2:
> ./include/linux/fortify-string.h:588:25: warning: call to '__read_overflow2_field'
> declared with attribute warning: detected read beyond size of field (2nd parameter);
> maybe use struct_group()? [-Wattribute-warning]
>   588 |                         __read_overflow2_field(q_size_field, size);
>       |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ...
>
> This call to 'memcpy()' is interpreted as an attempt to copy TX_OVERHEAD
> (which is 8) bytes from 4-byte 'sop' field of 'struct tx_pkt_info' and
> thus overread warning is issued. Since we actually want to copy both
> 'sop' and 'seg' fields at once, use the convenient 'struct_group()' here.
>
> Signed-off-by: Dmitry Antipov <dmantipov@...dex.ru>
> ---
> v2: prefer 'sizeof_field(struct tx_pkt_info, tx_overhead)' over the
> hardcoded constant (Jakub Kicinski)
> ---
>  drivers/net/ethernet/asix/ax88796c_main.c | 2 +-
>  drivers/net/ethernet/asix/ax88796c_main.h | 8 +++++---
>  2 files changed, 6 insertions(+), 4 deletions(-)
>

Acked-by: Łukasz Stelmach <l.stelmach@...sung.com>

> diff --git a/drivers/net/ethernet/asix/ax88796c_main.c b/drivers/net/ethernet/asix/ax88796c_main.c
> index e551ffaed20d..11e8996b33d7 100644
> --- a/drivers/net/ethernet/asix/ax88796c_main.c
> +++ b/drivers/net/ethernet/asix/ax88796c_main.c
> @@ -284,7 +284,7 @@ ax88796c_tx_fixup(struct net_device *ndev, struct sk_buff_head *q)
>  	ax88796c_proc_tx_hdr(&info, skb->ip_summed);
>  
>  	/* SOP and SEG header */
> -	memcpy(skb_push(skb, TX_OVERHEAD), &info.sop, TX_OVERHEAD);
> +	memcpy(skb_push(skb, TX_OVERHEAD), &info.tx_overhead, TX_OVERHEAD);
>  
>  	/* Write SPI TXQ header */
>  	memcpy(skb_push(skb, spi_len), ax88796c_tx_cmd_buf, spi_len);
> diff --git a/drivers/net/ethernet/asix/ax88796c_main.h b/drivers/net/ethernet/asix/ax88796c_main.h
> index 4a83c991dcbe..68a09edecab8 100644
> --- a/drivers/net/ethernet/asix/ax88796c_main.h
> +++ b/drivers/net/ethernet/asix/ax88796c_main.h
> @@ -25,7 +25,7 @@
>  #define AX88796C_PHY_REGDUMP_LEN	14
>  #define AX88796C_PHY_ID			0x10
>  
> -#define TX_OVERHEAD			8
> +#define TX_OVERHEAD     sizeof_field(struct tx_pkt_info, tx_overhead)
>  #define TX_EOP_SIZE			4
>  
>  #define AX_MCAST_FILTER_SIZE		8
> @@ -549,8 +549,10 @@ struct tx_eop_header {
>  };
>  
>  struct tx_pkt_info {
> -	struct tx_sop_header sop;
> -	struct tx_segment_header seg;
> +	struct_group(tx_overhead,
> +		struct tx_sop_header sop;
> +		struct tx_segment_header seg;
> +	);
>  	struct tx_eop_header eop;
>  	u16 pkt_len;
>  	u16 seq_num;

-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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