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Tue, 07 Apr 2026 08:33:57 -0700 (PDT) Received: from [192.168.88.32] ([212.105.153.231]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4887e83682fsm588473115e9.7.2026.04.07.08.33.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Apr 2026 08:33:56 -0700 (PDT) Message-ID: <0ab00cb4-8335-472d-b43e-3bbd99b41480@redhat.com> Date: Tue, 7 Apr 2026 17:33:55 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 5/5] net: qrtr: ns: Fix use-after-free in driver remove() To: manivannan.sadhasivam@oss.qualcomm.com, Manivannan Sadhasivam , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Simon Horman Cc: linux-arm-msm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260403-qrtr-fix-v2-0-f88a14859c63@oss.qualcomm.com> <20260403-qrtr-fix-v2-5-f88a14859c63@oss.qualcomm.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20260403-qrtr-fix-v2-5-f88a14859c63@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/3/26 6:06 PM, Manivannan Sadhasivam via B4 Relay wrote: > From: Manivannan Sadhasivam > > In the remove callback, if a packet arrives after destroy_workqueue() is > called, but before sock_release(), the qrtr_ns_data_ready() callback will > try to queue the work, causing use-after-free issue. > > Fix this issue by saving the default 'sk_data_ready' callback during > qrtr_ns_init() and use it to replace the qrtr_ns_data_ready() callback at > the start of remove(). This ensures that even if a packet arrives after > destroy_workqueue(), the work struct will not be dereferenced. > > Cc: stable@vger.kernel.org > Fixes: 0c2204a4ad71 ("net: qrtr: Migrate nameservice to kernel from userspace") > Signed-off-by: Manivannan Sadhasivam > --- > net/qrtr/ns.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/net/qrtr/ns.c b/net/qrtr/ns.c > index dfb5dad9473c..c62d79e03d64 100644 > --- a/net/qrtr/ns.c > +++ b/net/qrtr/ns.c > @@ -25,6 +25,7 @@ static struct { > u32 lookup_count; > struct workqueue_struct *workqueue; > struct work_struct work; > + void (*saved_data_ready)(struct sock *sk); > int local_node; > } qrtr_ns; > > @@ -754,6 +755,7 @@ int qrtr_ns_init(void) > goto err_sock; > } > > + qrtr_ns.saved_data_ready = qrtr_ns.sock->sk->sk_data_ready; > qrtr_ns.sock->sk->sk_data_ready = qrtr_ns_data_ready; > > sq.sq_port = QRTR_PORT_CTRL; > @@ -803,6 +805,10 @@ EXPORT_SYMBOL_GPL(qrtr_ns_init); > > void qrtr_ns_remove(void) > { > + write_lock_bh(&qrtr_ns.sock->sk->sk_callback_lock); > + qrtr_ns.sock->sk->sk_data_ready = qrtr_ns.saved_data_ready; > + write_unlock_bh(&qrtr_ns.sock->sk->sk_callback_lock); Sashiko says: --- Does this lock adequately protect against concurrent callback execution? In the network receive path, __sock_queue_rcv_skb() typically evaluates !sock_flag(sk, SOCK_DEAD) and invokes sk->sk_data_ready() locklessly, without acquiring sk_callback_lock or being in an RCU read-side critical section. If a thread processing a packet fetches the qrtr_ns_data_ready pointer and is preempted, could it resume and execute the callback after qrtr_ns_remove() has already finished destroying the workqueue? --- There are more remarks from sashiko: https://sashiko.dev/#/patchset/20260403-qrtr-fix-v2-0-f88a14859c63%40oss.qualcomm.com AFAICS they are pre-existing issues or false positive, but please have a look. /P