netdev - Re: [PATCH v1] netfilter: nf_tables: fix nft_set_elem

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Date:   Sat, 2 Jul 2022 11:59:48 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Hugues ANGUELKOV <hanguelkov@...dorisec.fr>
Cc:     netdev@...r.kernel.org, security@...nel.org, pablo@...filter.org,
        kadlec@...filter.org, fw@...len.de, davy <davy@...dorisec.fr>,
        amongodin@...dorisec.fr, torvalds@...uxfoundation.org
Subject: Re: [PATCH v1] netfilter: nf_tables: fix nft_set_elem_init heap
 buffer overflow

On Sat, 2 Jul 2022 19:59:11 +0200 Hugues ANGUELKOV wrote:
> From d91007a18140e02a1f12c9627058a019fe55b8e6 Mon Sep 17 00:00:00 2001
> From: Arthur Mongodin <amongodin@...dorisec.fr>
> Date: Sat, 2 Jul 2022 17:11:48 +0200
> Subject: [PATCH v1] netfilter: nf_tables: fix nft_set_elem_init heap buffer
>  overflow

You have the headers twice, you may want to trim them or use git
send-email if v2 is needed.

> The length used for the memcpy in nft_set_elem_init may exceed the bound
> of the allocated object due to a weak check in nft_setelem_parse_data.
> As a user can add an element with a data type NFT_DATA_VERDICT to a set
> with a data type different of NFT_DATA_VERDICT, then the comparison on the
> data type of the element allows to avoid the comparaison on the data length
> This fix forces the length comparison in nft_setelem_parse_data by removing
> the check for NFT_DATA_VERDICT type.

> Fixes: fdb9c405e35b ("netfilter: nf_tables: allow up to 64 bytes in the set element data area")
> Signed-off-by: Arthur Mongodin <amongodin@...dorisec.fr>
> ---
>  net/netfilter/nf_tables_api.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 51144fc66889..07845f211f3e 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -5219,7 +5219,7 @@ static int nft_setelem_parse_data(struct nft_ctx *ctx, struct nft_set *set,
>  	if (err < 0)
>  		return err;
>  
> -	if (desc->type != NFT_DATA_VERDICT && desc->len != set->dlen) {
> +	if (desc->len != set->dlen) {

Looking at the commit under fixes it seems like it changes the check
from desc->type != ... to set->type != ...

Seems like either the bug is even older or the fix should be to go back
to checking set->type. Prolly the former?