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From: Paolo Abeni <pabeni@redhat.com>
To: Eric Dumazet <edumazet@kernel.org>,
	"David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>
Cc: Simon Horman <horms@kernel.org>, David Ahern <dsahern@kernel.org>,
	Ido Schimmel <idosch@nvidia.com>,
	netdev@vger.kernel.org, stable@vger.kernel.org,
	Kyle Zeng <kylebot@openai.com>, Florian Westphal <fw@strlen.de>
Subject: Re: [PATCH v2 net] inet: frags: limit the truesize of a reassembly queue
Date: Mon, 2 Nov 2026 16:04:23 +0100	[thread overview]
Message-ID: <24feda7d-ae49-45af-9596-2cc5f149f28e@redhat.com> (raw)
In-Reply-To: <20261030081225.2575462-1-edumazet@kernel.org>

On 10/30/26 09:12, Eric Dumazet wrote:
> The truesize of fragments in a reassembly queue is only bounded by
> the per netns ipfrag_high_thresh sysctl, which has no upper limit.
> 
> inet_frag_reasm_finish() sums the truesize of all fragments in an int.
> If this sum reaches 2^32, it wraps, and the final sk_wmem_alloc
> adjustment of the socket owning the reassembled skb can cancel its own
> reference, leading to a use-after-free of this socket.
> 
> This can be triggered from an unprivileged user/network namespace,
> raising ipfrag_high_thresh and using padded TUN packets, which keep
> a large truesize after being trimmed by ip_rcv_core().

Clasiko infers a similar scenario is still reachable using multiple
concurrent frag queues:

https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20261030081225.2575462-1-edumazet@kernel.org

I'm unsure if that should be dealt with separately?!?

Thanks,

Paolo


  parent reply	other threads:[~2026-11-02 15:04 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-30  8:12 [PATCH v2 net] inet: frags: limit the truesize of a reassembly queue Eric Dumazet
2026-11-02  9:03 ` Ido Schimmel
2026-11-02 15:04 ` Paolo Abeni [this message]
2026-11-02 15:53   ` Eric Dumazet
2026-11-02 15:22 ` Jiayuan Chen
2026-11-02 18:50 ` Wang Zhan
2026-11-02 21:10 ` patchwork-bot+netdevbpf

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