linux-kernel - Re: [PATCH] net/tls: Fix sk_psock refcnt leak in bpf_exec_tx

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Message-Id: <20200427.111757.1063040756096170355.davem@davemloft.net>
Date:   Mon, 27 Apr 2020 11:17:57 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     xiyuyang19@...an.edu.cn
Cc:     borisp@...lanox.com, aviadye@...lanox.com,
        john.fastabend@...il.com, daniel@...earbox.net, kuba@...nel.org,
        ast@...nel.org, kafai@...com, songliubraving@...com, yhs@...com,
        andriin@...com, kpsingh@...omium.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        yuanxzhang@...an.edu.cn, kjlu@....edu, tanxin.ctf@...il.com
Subject: Re: [PATCH] net/tls: Fix sk_psock refcnt leak in
 bpf_exec_tx_verdict()

From: Xiyu Yang <xiyuyang19@...an.edu.cn>
Date: Sat, 25 Apr 2020 20:54:37 +0800

> bpf_exec_tx_verdict() invokes sk_psock_get(), which returns a reference
> of the specified sk_psock object to "psock" with increased refcnt.
> 
> When bpf_exec_tx_verdict() returns, local variable "psock" becomes
> invalid, so the refcount should be decreased to keep refcount balanced.
> 
> The reference counting issue happens in one exception handling path of
> bpf_exec_tx_verdict(). When "policy" equals to NULL but "psock" is not
> NULL, the function forgets to decrease the refcnt increased by
> sk_psock_get(), causing a refcnt leak.
> 
> Fix this issue by calling sk_psock_put() on this error path before
> bpf_exec_tx_verdict() returns.
> 
> Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.com>

Applied and queued up for -stable.