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

Marc Kleine-Budde
2021-08-18T06:27:33Z

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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@grandegger.com>
> Cc: Marc Kleine-Budde <mkl@pengutronix.de>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: linux-can@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Acked-by: Marc Kleine-Budde <mkl@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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