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[208.53.111.167]) by smtp.gmail.com with ESMTPSA id ix9-20020a170902f80900b001782a0d3eeasm2190688plb.115.2022.11.17.19.09.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Nov 2022 19:09:37 -0800 (PST) Message-ID: Date: Thu, 17 Nov 2022 19:09:36 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: [PATCH v2] tty:synclink_gt unwind actions in error path Content-Language: en-US To: Zhengchao Shao , linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, jirislaby@kernel.org Cc: akpm@linux-foundation.org, weiyongjun1@huawei.com, yuehaibing@huawei.com References: <20221114010734.314910-1-shaozhengchao@huawei.com> From: Paul Fulghum In-Reply-To: <20221114010734.314910-1-shaozhengchao@huawei.com> X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1749803459673866011?= X-GMAIL-MSGID: =?utf-8?q?1749803459673866011?= synclink_gt.c:hdlcdev_open() does not properly unwind actions in error path. Unwound action 1: try_module_get(THIS_MODULE) Change d4c63b7c7450 added try_module_get()/module_put() to stop WARN_ON if modprobe -r removes synclink_gt while net device is open. This is same as drivers/wan/farsync.c. Other generic HDLC hardware drivers do not do this. On unload, synclink_gt calls drivers/wan/hdlc.c:unregister_hdlc_device() which calls down to net/sched/sch_generic.c:dev_shutdown() triggering WARN_ON(timer_pending(&dev->watchdog_timer)); if net device is open. try_module_get/module_put, a disfavored pattern, is replaced by a call to dev_close() for open net device before calling unregister_hdlc_device() when driver unloads. This pevents WARN_ON. Unwound action 2: drivers/wan/hdlc.c:hdlc_open() This is moved to after driver level init/checks with proper rollback of previous actions. This is a more sensible ordering as the most common error paths are at the driver level and the driver level rollbacks require less processing than hdlc_open()/hdlc_close(). Fixes: d4c63b7c7450 ("synclink_gt fix module reference") Fixes: 705b6c7b34f2 ("[PATCH] new driver synclink_gt") Suggested-by: Zhengchao Shao Tested-by: Paul Fulghum Signed-off-by: Paul Fulghum --- V1 -> V2: improve description, add dev_close call drivers/tty/synclink_gt.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c index 25e9befdda3a..5921703f7228 100644 --- a/drivers/tty/synclink_gt.c +++ b/drivers/tty/synclink_gt.c @@ -70,6 +70,7 @@ #include #include #include +#include #include #include @@ -1433,16 +1434,8 @@ static int hdlcdev_open(struct net_device *dev) int rc; unsigned long flags; - if (!try_module_get(THIS_MODULE)) - return -EBUSY; - DBGINFO(("%s hdlcdev_open\n", dev->name)); - /* generic HDLC layer open processing */ - rc = hdlc_open(dev); - if (rc) - return rc; - /* arbitrate between network and tty opens */ spin_lock_irqsave(&info->netlock, flags); if (info->port.count != 0 || info->netcount != 0) { @@ -1461,6 +1454,16 @@ static int hdlcdev_open(struct net_device *dev) return rc; } + /* generic HDLC layer open processing */ + rc = hdlc_open(dev); + if (rc) { + shutdown(info); + spin_lock_irqsave(&info->netlock, flags); + info->netcount = 0; + spin_unlock_irqrestore(&info->netlock, flags); + return rc; + } + /* assert RTS and DTR, apply hardware settings */ info->signals |= SerialSignal_RTS | SerialSignal_DTR; program_hw(info); @@ -1506,7 +1509,6 @@ static int hdlcdev_close(struct net_device *dev) info->netcount=0; spin_unlock_irqrestore(&info->netlock, flags); - module_put(THIS_MODULE); return 0; } @@ -1742,6 +1744,11 @@ static void hdlcdev_exit(struct slgt_info *info) { if (!info->netdev) return; + if (info->netcount) { + rtnl_lock(); + dev_close(info->netdev); + rtnl_unlock(); + } unregister_hdlc_device(info->netdev); free_netdev(info->netdev); info->netdev = NULL;