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

Christophe Leroy
2021-08-18T06:50:21Z

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@kernel.crashing.org>
> Cc: Qinglang Miao <miaoqinglang@huawei.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: Hulk Robot <hulkci@huawei.com>
> Cc: Wang Wensheng <wangwensheng4@huawei.com>
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
> Link: https://lore.kernel.org/lkml/87czqsnmw9.fsf@mpe.ellerman.id.au
> ---
> 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;
>