From: Florian Westphal <fw@strlen.de>
To: Zhiling Zou <zhilinz@nebusec.ai>
Cc: netfilter-devel@vger.kernel.org, netdev@vger.kernel.org,
pablo@netfilter.org, phil@nwl.cc, kadlec@netfilter.org,
den@openvz.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, horms@kernel.org,
xmei5@asu.edu, kees@kernel.org, sbrivio@redhat.com,
vega@nebusec.ai
Subject: Re: [PATCH nf 1/1] netfilter: ipset: serialize kernel-side put-byindex with swap
Date: Sat, 1 Aug 2026 15:55:42 +0200 [thread overview]
Message-ID: <am363vHJsdnL3Ja-@strlen.de> (raw)
In-Reply-To: <df40376603e2a53a311d5ceea63240bedc11bdfc.1785583673.git.zhilinz@nebusec.ai>
Zhiling Zou <zhilinz@nebusec.ai> wrote:
> list:set garbage collection drops member set references through
> ip_set_put_byindex(), which resolves inst->ip_set_list[index] before
> __ip_set_put() takes ip_set_ref_lock. ip_set_swap() swaps both the set
> pointers and the corresponding refcounts while holding that same lock.
>
> If garbage collection looks up the old set pointer for an index and then
> loses the lock race to ip_set_swap(), it decrements the old object after
> its refcount has already been swapped away. This can trigger BUG_ON(ref
> == 0) when the other set had no references, or otherwise under-reference
> a set that is still reachable through the swapped index.
>
> Fix this by holding ip_set_ref_lock across the kernel-side lookup and
> refcount decrement. This keeps ip_set_put_byindex() paired with the same
> set/ref state that ip_set_swap() publishes, without changing normal
> list:set deletion or swap behaviour.
Looks like a duplicate of
https://patchwork.ozlabs.org/project/netfilter-devel/patch/20260722223832.3524006-1-xmei5@asu.edu/
prev parent reply other threads:[~2026-08-01 13:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-01 12:10 [PATCH nf 0/1] netfilter: ipset: serialize kernel-side put-byindex with swap Zhiling Zou
2026-08-01 12:10 ` [PATCH nf 1/1] " Zhiling Zou
2026-08-01 13:55 ` Florian Westphal [this message]
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