linux-kernel - Re: [PATCH 58/64] powerpc: Split memset() to avoid multi-field overflow

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Date:   Thu, 05 Aug 2021 21:36:54 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Kees Cook <keescook@...omium.org>, linux-hardening@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Keith Packard <keithpac@...zon.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...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
Subject: Re: [PATCH 58/64] powerpc: Split memset() to avoid multi-field
 overflow

Kees Cook <keescook@...omium.org> writes:
> 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.
>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  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);
>  		break;
>  	case SMU_I2C_TRANSFER_COMBINED:
>  		cmd->info.devaddr &= 0xfe;
> -- 
> 2.30.2

Reviewed-by: Michael Ellerman <mpe@...erman.id.au>

cheers