Re: [PATCH net 1/3] net: stmmac: replace memcpy with strscpy in ethtool

[Jakub Kicinski <kuba@kernel.org>]

On Thu, 28 Aug 2025 12:02:35 +0200 Konrad Leszczynski wrote:
> Fix kernel exception by replacing memcpy with strscpy when used with
> safety feature strings in ethtool logic.
> 
> [  +0.000023] BUG: KASAN: global-out-of-bounds in stmmac_get_strings+0x17d/0x520 [stmmac]
> [  +0.000115] Read of size 32 at addr ffffffffc0cfab20 by task ethtool/2571

If you hit this with upstream code please mention which string 
is not padded. If this can't happen with upstream platforms --
there is no upstream bug. BTW ethtool_puts() is a better choice.

> Fixes: 8bf993a5877e8a0a ("net: stmmac: Add support for DWMAC5 and implement Safety Features")
> Reviewed-by: Sebastian Basierski <sebastian.basierski@intel.com>
> Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
> Signed-off-by: Konrad Leszczynski <konrad.leszczynski@intel.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
> index 77758a7299b4..0433be4bd0c4 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
> @@ -752,7 +752,7 @@ static void stmmac_get_strings(struct net_device *dev, u32 stringset, u8 *data)
>  				if (!stmmac_safety_feat_dump(priv,
>  							&priv->sstats, i,
>  							NULL, &desc)) {
> -					memcpy(p, desc, ETH_GSTRING_LEN);
> +					strscpy(p, desc, ETH_GSTRING_LEN);
>  					p += ETH_GSTRING_LEN;
>  				}