linux-hardening - Re: [PATCH][next] mlxsw: spectrum_kvdl: Use struct

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Date:   Wed, 26 Jan 2022 11:55:04 +0100
From:   Petr Machata <petrm@...dia.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
CC:     Ido Schimmel <idosch@...dia.com>, Petr Machata <petrm@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-hardening@...r.kernel.org>
Subject: Re: [PATCH][next] mlxsw: spectrum_kvdl: Use struct_size() helper in
 kzalloc()


"Gustavo A. R. Silva" <gustavoars@...nel.org> writes:

> Make use of the struct_size() helper instead of an open-coded version,
> in order to avoid any potential type mistakes or integer overflows that,
> in the worst scenario, could lead to heap overflows.
>
> Also, address the following sparse warnings:
> drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c:229:24: warning: using sizeof on a flexible structure
>
> Link: https://github.com/KSPP/linux/issues/174
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c
> index a9fff8adc75e..d20e794e01ca 100644
> --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c
> +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c
> @@ -213,7 +213,6 @@ mlxsw_sp1_kvdl_part_init(struct mlxsw_sp *mlxsw_sp,
>  	struct mlxsw_sp1_kvdl_part *part;
>  	bool need_update = true;
>  	unsigned int nr_entries;
> -	size_t usage_size;
>  	u64 resource_size;
>  	int err;
>  
> @@ -225,8 +224,8 @@ mlxsw_sp1_kvdl_part_init(struct mlxsw_sp *mlxsw_sp,
>  	}
>  
>  	nr_entries = div_u64(resource_size, info->alloc_size);
> -	usage_size = BITS_TO_LONGS(nr_entries) * sizeof(unsigned long);
> -	part = kzalloc(sizeof(*part) + usage_size, GFP_KERNEL);
> +	part = kzalloc(struct_size(part, usage, BITS_TO_LONGS(nr_entries)),
> +		       GFP_KERNEL);
>  	if (!part)
>  		return ERR_PTR(-ENOMEM);

Reviewed-by: Petr Machata <petrm@...dia.com>