Re: [PATCH v2 61/63] powerpc: Split memset() to avoid multi-field overflow

[Christophe Leroy]

Le 18/08/2021 à 08:05, Kees Cook a écrit :
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memset(), avoid intentionally writing across
> neighboring fields.
>
> Instead of writing across a field boundary with memset(), move the call
> to just the array, and an explicit zeroing of the prior field.
>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Qinglang Miao <miaoqinglang@xxxxxxxxxx>
> Cc: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx>
> Cc: Hulk Robot <hulkci@xxxxxxxxxx>
> Cc: Wang Wensheng <wangwensheng4@xxxxxxxxxx>
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Reviewed-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Link: https://lore.kernel.org/lkml/87czqsnmw9.fsf@xxxxxxxxxxxxxxxxxx
> ---
>   drivers/macintosh/smu.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/macintosh/smu.c b/drivers/macintosh/smu.c
> index 94fb63a7b357..59ce431da7ef 100644
> --- a/drivers/macintosh/smu.c
> +++ b/drivers/macintosh/smu.c
> @@ -848,7 +848,8 @@ int smu_queue_i2c(struct smu_i2c_cmd *cmd)
>   	cmd->read = cmd->info.devaddr & 0x01;
>   	switch(cmd->info.type) {
>   	case SMU_I2C_TRANSFER_SIMPLE:
> -		memset(&cmd->info.sublen, 0, 4);
> +		cmd->info.sublen = 0;
> +		memset(&cmd->info.subaddr, 0, 3);

subaddr[] is a table, should the & be avoided ?
And while at it, why not use sizeof(subaddr) instead of 3 ?


>   		break;
>   	case SMU_I2C_TRANSFER_COMBINED:
>   		cmd->info.devaddr &= 0xfe;