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Date: Thu, 12 Mar 2026 12:02:37 +0100
From: Florian Westphal <fw@strlen.de>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: [PATCH nf] nf_tables: nft_dynset: fix possible stateful
 expression memleak in error path
Message-ID: <abKdTesNowf_-h3F@strlen.de>
References: <20260312101120.3512073-1-pablo@netfilter.org>
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In-Reply-To: <20260312101120.3512073-1-pablo@netfilter.org>

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> If cloning the second stateful expression in the element via GFP_ATOMIC
> fails, then the first stateful expression remains in place without being
> released.
> 
>    unreferenced object (percpu) 0x607b97e9cab8 (size 16):
>      comm "softirq", pid 0, jiffies 4294931867
>      hex dump (first 16 bytes on cpu 3):
>        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>      backtrace (crc 0):
>        pcpu_alloc_noprof+0x453/0xd80
>        nft_counter_clone+0x9c/0x190 [nf_tables]
>        nft_expr_clone+0x8f/0x1b0 [nf_tables]
>        nft_dynset_new+0x2cb/0x5f0 [nf_tables]
>        nft_rhash_update+0x236/0x11c0 [nf_tables]
>        nft_dynset_eval+0x11f/0x670 [nf_tables]
>        nft_do_chain+0x253/0x1700 [nf_tables]
>        nft_do_chain_ipv4+0x18d/0x270 [nf_tables]
>        nf_hook_slow+0xaa/0x1e0
>        ip_local_deliver+0x209/0x330
> 
> Pass NULL to nft_set_elem_expr_destroy() given stateful expressions do
> not require context at this stage.

static void nft_connlimit_do_destroy(const struct nft_ctx *ctx,
                                     struct nft_connlimit *priv)
{
        nf_ct_netns_put(ctx->net, ctx->family);
        nf_conncount_cache_free(priv->list);
        kfree(priv->list);
}

I think minimal fake context could work though, the clone wasn't
exposed to other cpus yet.

Other than this patch looks correct to me.