Re: [PATCH v2 59/63] can: flexcan: Use struct_group() to zero struct flexcan_regs regions

[Marc Kleine-Budde]

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 <w...@grandegger.com>
> Cc: Marc Kleine-Budde <m...@pengutronix.de>
> Cc: "David S. Miller" <da...@davemloft.net>
> Cc: Jakub Kicinski <k...@kernel.org>
> Cc: linux-...@vger.kernel.org
> Cc: net...@vger.kernel.org
> Signed-off-by: Kees Cook <keesc...@chromium.org>

Acked-by: Marc Kleine-Budde <m...@pengutronix.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

-- 
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