Re: [PATCH net] rtnetlink: not allow dev gro_max_size to exceed GRO_MAX_SIZE

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 19 May 2023 13:16:08 -0400
Xin Long <lucien.xin@gmail.com> wrote:

> In commit 0fe79f28bfaf ("net: allow gro_max_size to exceed 65536"),
> it limited GRO_MAX_SIZE to (8 * 65535) to avoid overflows, but also
> deleted the check of GRO_MAX_SIZE when setting the dev gro_max_size.
> 
> Currently, dev gro_max_size can be set up to U32_MAX (0xFFFFFFFF),
> and GRO_MAX_SIZE is not even used anywhere.
> 
> This patch brings back the GRO_MAX_SIZE check when setting dev
> gro_max_size/gro_ipv4_max_size by users.
> 
> Fixes: 0fe79f28bfaf ("net: allow gro_max_size to exceed 65536")
> Reported-by: Xiumei Mu <xmu@redhat.com>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>
> ---
>  net/core/rtnetlink.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 653901a1bf75..59b24b184cb0 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -2886,6 +2886,11 @@ static int do_setlink(const struct sk_buff *skb,
>  	if (tb[IFLA_GRO_MAX_SIZE]) {
>  		u32 gro_max_size = nla_get_u32(tb[IFLA_GRO_MAX_SIZE]);
>  
> +		if (gro_max_size > GRO_MAX_SIZE) {
> +			err = -EINVAL;
> +			goto errout;
> +		}
> +

Please add extack messages so the error can be reported better.