From: Qingfang Deng <qingfang.deng@linux.dev>
To: Norbert Szetei <norbert@doyensec.com>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Breno Leitao <leitao@debian.org>,
Taegu Ha <hataegu0826@gmail.com>, Kees Cook <kees@kernel.org>,
linux-ppp@vger.kernel.org, linux-kernel@vger.kernel.org,
Guillaume Nault <gnault@redhat.com>,
netdev@vger.kernel.org
Subject: Re: [PATCH net v2] ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF
Date: Fri, 3 Jul 2026 15:27:00 +0800 [thread overview]
Message-ID: <de2616b3-6edf-4255-ba77-0674e225ab27@linux.dev> (raw)
In-Reply-To: <D9C0245B-608B-4884-8A09-F55BA4A9F948@doyensec.com>
Hi,
On 2026/7/2 2:12, Norbert Szetei wrote:
> +/* Purge after the grace period: a late ppp_input() may still queue an
> + * skb on pch->file.rq before the last RCU reader drains.
> + */
> +static void ppp_release_channel_free(struct rcu_head *rcu)
> +{
> + struct channel *pch = container_of(rcu, struct channel, rcu);
> +
> + skb_queue_purge(&pch->file.xq);
> + skb_queue_purge(&pch->file.rq);
> + kfree(pch);
> +}
> +
> /*
> * Drop a reference to a ppp channel and free its memory if the refcount reaches
> * zero.
> @@ -3581,9 +3594,7 @@ static void ppp_release_channel(struct channel *pch)
> pr_err("ppp: destroying undead channel %p !\n", pch);
> return;
> }
> - skb_queue_purge(&pch->file.xq);
> - skb_queue_purge(&pch->file.rq);
> - kfree(pch);
> + call_rcu(&pch->rcu, ppp_release_channel_free);
> }
>
> static void __exit ppp_cleanup(void)
AI-review found an issue:
https://sashiko.dev/#/patchset/D9C0245B-608B-4884-8A09-F55BA4A9F948%40doyensec.com
An rcu_barrier() call is needed at the end of ppp_cleanup().
Regards,
Qingfang
next prev parent reply other threads:[~2026-07-03 7:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-01 18:12 [PATCH net v2] ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF Norbert Szetei
2026-07-02 8:19 ` Qingfang Deng
2026-07-03 16:05 ` Guillaume Nault
2026-07-03 7:27 ` Qingfang Deng [this message]
2026-07-03 16:32 ` Breno Leitao
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