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Mon, 14 Sep 2026 20:54:15 -0700 (PDT) Received: from SGN-LDSENG.tasernet.com ([2405:4800:5cc3:11a:1ac0:4dff:fe8b:4a69]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39dfdd0baaasm2385768a91.9.2026.09.14.20.54.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 20:54:15 -0700 (PDT) From: Cong Nguyen To: Guenter Roeck Cc: Simon Guinot , linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] hwmon: (gpio-fan) fix use-after-free of alarm_work on unbind Date: Tue, 15 Sep 2026 10:54:09 +0700 Message-Id: <20260915035409.4177780-1-congnt264@gmail.com> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: linux-hwmon@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit fan_alarm_irq_handler() schedules alarm_work, but nothing ever cancels it. free_irq() (via devm) only waits for an in-progress IRQ handler, not queued work -- a pending alarm_work can run after fan_data is devm-freed, dereferencing it in fan_alarm_notify(). Cancel it via a devm action registered before devm_request_irq(), so teardown frees the IRQ first, then cancels whatever's already queued. Guenter pointed out cancel_work_sync() still leaves a window if something schedules the work again after it's canceled; use disable_work_sync() instead, which permanently disables it too. Fixes: d6fe1360f42e ("hwmon: add generic GPIO fan driver") Reported-by: Sashiko AI review Link: https://lore.kernel.org/r/20260830152150.27F5F1F000E9@smtp.kernel.org Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4 Signed-off-by: Cong Nguyen --- Changes in v2: - Use disable_work_sync() instead of cancel_work_sync(), per Guenter: cancel_work_sync() only drains the current instance, so anything that calls schedule_work() again afterward would still requeue it. disable_work_sync() permanently disables the work item too. drivers/hwmon/gpio-fan.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/drivers/hwmon/gpio-fan.c b/drivers/hwmon/gpio-fan.c index 084828e1e281..28cfd50aa859 100644 --- a/drivers/hwmon/gpio-fan.c +++ b/drivers/hwmon/gpio-fan.c @@ -81,9 +81,16 @@ static ssize_t fan1_alarm_show(struct device *dev, static DEVICE_ATTR_RO(fan1_alarm); +static void gpio_fan_cancel_alarm_work(void *data) +{ + struct gpio_fan_data *fan_data = data; + + disable_work_sync(&fan_data->alarm_work); +} + static int fan_alarm_init(struct gpio_fan_data *fan_data) { - int alarm_irq; + int alarm_irq, err; struct device *dev = fan_data->dev; /* @@ -95,6 +102,17 @@ static int fan_alarm_init(struct gpio_fan_data *fan_data) return 0; INIT_WORK(&fan_data->alarm_work, fan_alarm_notify); + + /* + * Register before devm_request_irq() below: LIFO teardown must free + * the IRQ (stopping new schedule_work() calls) before this cancels + * whatever alarm_work is already queued or running. + */ + err = devm_add_action_or_reset(dev, gpio_fan_cancel_alarm_work, + fan_data); + if (err) + return err; + irq_set_irq_type(alarm_irq, IRQ_TYPE_EDGE_BOTH); return devm_request_irq(dev, alarm_irq, fan_alarm_irq_handler, IRQF_SHARED, "GPIO fan alarm", fan_data); -- 2.25.1