From: Tom Parkin <tparkin@katalix.com>
To: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Cc: "David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Cong Wang <cong.wang@bytedance.com>,
Randy Dunlap <rdunlap@infradead.org>,
Xin Xiong <xiongx18@fudan.edu.cn>,
"Gong, Sishuai" <sishuai@purdue.edu>,
Matthias Schiffer <mschiffer@universe-factory.net>,
Bhaskar Chowdhury <unixbhaskar@gmail.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
yuanxzhang@fudan.edu.cn, Xin Tan <tanxin.ctf@gmail.com>
Subject: Re: [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core
Date: Thu, 9 Sep 2021 10:01:56 +0100 [thread overview]
Message-ID: <20210909090156.GA7098@katalix.com> (raw)
In-Reply-To: <1631161930-77772-1-git-send-email-xiyuyang19@fudan.edu.cn>
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On Thu, Sep 09, 2021 at 12:32:00 +0800, Xiyu Yang wrote:
> The reference count leak issue may take place in an error handling
> path. If both conditions of tunnel->version == L2TP_HDR_VER_3 and the
> return value of l2tp_v3_ensure_opt_in_linear is nonzero, the function
> would directly jump to label invalid, without decrementing the reference
> count of the l2tp_session object session increased earlier by
> l2tp_tunnel_get_session(). This may result in refcount leaks.
I agree with your analysis. Thanks for catching this!
>
> Fix this issue by decrease the reference count before jumping to the
> label invalid.
>
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
> ---
> net/l2tp/l2tp_core.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
> index 53486b162f01..93271a2632b8 100644
> --- a/net/l2tp/l2tp_core.c
> +++ b/net/l2tp/l2tp_core.c
> @@ -869,8 +869,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
> }
>
> if (tunnel->version == L2TP_HDR_VER_3 &&
> - l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
> + l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
> + l2tp_session_dec_refcount(session);
> goto invalid;
> + }
The error paths in l2tp_udp_recv_core are a bit convoluted because of
the check (!session || !session->recv_skb) which may or may not need
to drop a session reference if triggered.
I think it could be simplified since session->recv_skb is always set
for all the current session types in the tree, but doing that is probably
a little patch series on its own.
>
> l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
> l2tp_session_dec_refcount(session);
> --
> 2.7.4
>
--
Tom Parkin
Katalix Systems Ltd
https://katalix.com
Catalysts for your Embedded Linux software development
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next prev parent reply other threads:[~2021-09-09 9:07 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-09 4:32 [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core Xiyu Yang
2021-09-09 9:01 ` Tom Parkin [this message]
2021-09-09 9:10 ` Tom Parkin
2021-09-09 10:10 ` patchwork-bot+netdevbpf
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