linux-kernel - Re: [PATCH v2 59/63] can: flexcan: Use struct_group() to zero struct flexcan

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Message-ID: <20210818062657.6hvn75kf5o5cgey2@pengutronix.de>
Date:   Wed, 18 Aug 2021 08:26:57 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        Wolfgang Grandegger <wg@...ndegger.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-can@...r.kernel.org,
        netdev@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-wireless@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-staging@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 59/63] can: flexcan: Use struct_group() to zero struct
 flexcan_regs regions

On 17.08.2021 23:05:29, Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memset(), avoid intentionally writing across
> neighboring fields.
> 
> Add struct_group() to mark both regions of struct flexcan_regs that get
> initialized to zero. Avoid the future warnings:
> 
> In function 'fortify_memset_chk',
>     inlined from 'memset_io' at ./include/asm-generic/io.h:1169:2,
>     inlined from 'flexcan_ram_init' at drivers/net/can/flexcan.c:1403:2:
> ./include/linux/fortify-string.h:199:4: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
>   199 |    __write_overflow_field(p_size_field, size);
>       |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In function 'fortify_memset_chk',
>     inlined from 'memset_io' at ./include/asm-generic/io.h:1169:2,
>     inlined from 'flexcan_ram_init' at drivers/net/can/flexcan.c:1408:3:
> ./include/linux/fortify-string.h:199:4: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
>   199 |    __write_overflow_field(p_size_field, size);
>       |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Cc: Wolfgang Grandegger <wg@...ndegger.com>
> Cc: Marc Kleine-Budde <mkl@...gutronix.de>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: linux-can@...r.kernel.org
> Cc: netdev@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Acked-by: Marc Kleine-Budde <mkl@...gutronix.de>

> -	memset_io(&regs->mb[0][0], 0,
> -		  offsetof(struct flexcan_regs, rx_smb1[3]) -
> -		  offsetof(struct flexcan_regs, mb[0][0]) + 0x4);
> +	memset_io(&regs->init, 0, sizeof(regs->init));

This even makes the code more readable! \o/

>  	if (priv->can.ctrlmode & CAN_CTRLMODE_FD)
> -		memset_io(&regs->tx_smb_fd[0], 0,
> -			  offsetof(struct flexcan_regs, rx_smb1_fd[17]) -
> -			  offsetof(struct flexcan_regs, tx_smb_fd[0]) + 0x4);
> +		memset_io(&regs->init_fd, 0, sizeof(regs->init_fd));
>  
>  	reg_ctrl2 &= ~FLEXCAN_CTRL2_WRMFRZ;
>  	priv->write(reg_ctrl2, &regs->ctrl2);

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
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