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[61.222.64.201]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2e49f6ceaedsm2675645ad.49.2026.10.01.18.46.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Oct 2026 18:47:01 -0700 (PDT) From: Tim JH Chen To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, ilpo.jarvinen@linux.intel.com, johannes@sipsolutions.net, loic.poulain@oss.qualcomm.com, ryazanov.s.a@gmail.com, chandrashekar.devegowda@intel.com, haijun.liu@mediatek.com, ricardo.martinez@linux.intel.com, linux-kernel@vger.kernel.org, tim.jh.chen@wnc.com.tw, Chih.Hung.Huang@wnc.com.tw, Tim JH Chen Subject: [PATCH net v6 2/4] net: wwan: t7xx: do not exit the TX push kthread on resume failure Date: Fri, 2 Oct 2026 09:46:36 +0800 Message-ID: <20261002014638.47981-3-tim770802@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261002014638.47981-1-tim770802@gmail.com> References: <20261002014638.47981-1-tim770802@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit t7xx_dpmaif_tx_hw_push_thread() returns, ending the kthread, when pm_runtime_resume_and_get() fails with anything other than -EACCES. kthread_run() keeps no extra reference to the task, so the task_struct can be reaped while dpmaif_ctrl->tx_thread still points at it. A later t7xx_dpmaif_tx_thread_rel() then calls kthread_stop() on the stale pointer, which does get_task_struct() on freed memory: a use-after-free. It also stops TX permanently and silently. Log the failure and retry after a short back-off instead of exiting, so the thread stays alive until kthread_stop() tears it down. Fixes: 46e8f49ed7b3 ("net: wwan: t7xx: Introduce power management") Signed-off-by: Tim JH Chen --- drivers/net/wwan/t7xx/t7xx_hif_dpmaif_tx.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_tx.c b/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_tx.c index bd6116a8c541..2a405bc74312 100644 --- a/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_tx.c +++ b/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_tx.c @@ -447,6 +447,11 @@ static void t7xx_do_tx_hw_push(struct dpmaif_ctrl *dpmaif_ctrl) (dpmaif_ctrl->state == DPMAIF_STATE_PWRON)); } +/* Back-off before retrying a failed runtime PM resume in the TX push + * kthread, so a persistent error does not busy-loop. + */ +#define DPMAIF_TX_RESUME_RETRY_MS 20 + static int t7xx_dpmaif_tx_hw_push_thread(void *arg) { struct dpmaif_ctrl *dpmaif_ctrl = arg; @@ -466,8 +471,16 @@ static int t7xx_dpmaif_tx_hw_push_thread(void *arg) } ret = pm_runtime_resume_and_get(dpmaif_ctrl->dev); - if (ret < 0 && ret != -EACCES) - return ret; + if (ret < 0 && ret != -EACCES) { + /* Do not exit the thread: dpmaif_ctrl->tx_thread still + * points at this task and t7xx_dpmaif_tx_thread_rel() + * will call kthread_stop() on it. Back off and retry. + */ + dev_err_ratelimited(dpmaif_ctrl->dev, + "Failed to resume for TX push: %d\n", ret); + msleep_interruptible(DPMAIF_TX_RESUME_RETRY_MS); + continue; + } t7xx_pci_disable_sleep(dpmaif_ctrl->t7xx_dev); t7xx_do_tx_hw_push(dpmaif_ctrl); -- 2.43.0