netdev - Re: [PATCH net 1/1] netfilter: flowtable: Fix use after free after freeing flow table

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Date:   Fri, 19 Aug 2022 01:04:10 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Paul Blakey <paulb@...dia.com>
Cc:     Oz Shlomo <ozsh@...dia.com>, Roi Dayan <roid@...dia.com>,
        netdev@...r.kernel.org, Saeed Mahameed <saeedm@...dia.com>,
        netfilter-devel@...r.kernel.org
Subject: Re: [PATCH net 1/1] netfilter: flowtable: Fix use after free after
 freeing flow table

Hi Paul,

On Thu, Aug 18, 2022 at 10:27:54AM +0300, Paul Blakey wrote:
[...]
> diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
> index f2def06d1070..19fd3b5f8a1b 100644
> --- a/net/netfilter/nf_flow_table_core.c
> +++ b/net/netfilter/nf_flow_table_core.c
> @@ -605,6 +605,7 @@ void nf_flow_table_free(struct nf_flowtable *flow_table)
>  	mutex_unlock(&flowtable_lock);
>  
>  	cancel_delayed_work_sync(&flow_table->gc_work);
> +	nf_flow_table_offload_flush(flow_table);
>  	nf_flow_table_iterate(flow_table, nf_flow_table_do_cleanup, NULL);
>  	nf_flow_table_iterate(flow_table, nf_flow_offload_gc_step, NULL);
>  	nf_flow_table_offload_flush(flow_table);

patch looks very similar to:

https://patchwork.ozlabs.org/project/netfilter-devel/patch/1633854320-12326-1-git-send-email-volodymyr.mytnyk@plvision.eu/

I proposed these two instead to avoid reiterative calls to flush from
the cleanup path (see attached).

It should be possible to either take your patch to nf.git (easier for
-stable backport), then look into my patches for nf-next.git, would
you pick up on these follow up?

View attachment "0001-netfilter-flowtable-add-nf_flow_table_gc_run.patch" of type "text/x-diff" (2626 bytes)

View attachment "0002-netfilter-flowtable-fix-stuck-flows-on-cleanup-due-t.patch" of type "text/x-diff" (2633 bytes)