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Miller , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, syzbot+5ec223ccb83b24ef982f@syzkaller.appspotmail.com Subject: [PATCH net] atm: mpoa: fix mpc->dev refcount across mpoad restart Message-ID: <177555091252.59118.13093904987038690781@gmail.com> Date: Tue, 07 Apr 2026 14:20:12 +0545 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 atm: mpoa: fix mpc->dev refcount across mpoad restart mpoad_close() drops the reference held in mpc->dev with dev_put(), but the mpoa_client stays alive and keeps the same device pointer. A later mpoad attach reuses the existing mpoa_client without reacquiring that reference, so the next close can hit the netdevice refcount warning. Keep the LEC device reference with the mpoa_client until the device unregisters or the client is torn down. Reported-by: syzbot+5ec223ccb83b24ef982f@syzkaller.appspotmail.com Link: https://groups.google.com/g/syzkaller-bugs/c/qhZ5MJfLBOE/m/UnotmgRdAQAJ Signed-off-by: Shuvam Pandey --- net/atm/mpc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/atm/mpc.c b/net/atm/mpc.c index ce8e9780373b..1e9b9c633e8b 100644 --- a/net/atm/mpc.c +++ b/net/atm/mpc.c @@ -886,7 +886,6 @@ static void mpoad_close(struct atm_vcc *vcc) struct lec_priv *priv = netdev_priv(mpc->dev); priv->lane2_ops->associate_indicator = NULL; stop_mpc(mpc); - dev_put(mpc->dev); } mpc->in_ops->destroy_cache(mpc); @@ -1508,6 +1507,8 @@ static void __exit atm_mpoa_cleanup(void) priv = netdev_priv(mpc->dev); if (priv->lane2_ops != NULL) priv->lane2_ops->associate_indicator = NULL; + dev_put(mpc->dev); + mpc->dev = NULL; } ddprintk("about to clear caches\n"); mpc->in_ops->destroy_cache(mpc); -- 2.50.0