[RFC v1 1/3] workqueue: Add resource-managed version of INIT_[DELAYED_]WORK()

[Sven Van Asbroeck <thesven73@gmail.com>]

In modules which extensively use devm_ resource management, it is often
easy to overlook (delayed) work that is left pending or running after the
module is unloaded. This could introduce user-after-free issues.

Nudge kernel developers into 'doing the right thing' by introducing a
resource-managed version of INIT_[DELAYED_]WORK(). This can be used as
an elegant way to ensure that work is not left pending or running after
its dependencies are released.

Functions introduced in workqueue.h :
- devm_init_work()
- devm_init_delayed_work()

Signed-off-by: Sven Van Asbroeck <TheSven73@googlemail.com>
---
 include/linux/workqueue.h |  7 +++++
 kernel/workqueue.c        | 54 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 60d673e15632..eee148eb9908 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -15,6 +15,7 @@
 #include <linux/cpumask.h>
 #include <linux/rcupdate.h>
 
+struct device;
 struct workqueue_struct;
 
 struct work_struct;
@@ -670,4 +671,10 @@ int workqueue_offline_cpu(unsigned int cpu);
 int __init workqueue_init_early(void);
 int __init workqueue_init(void);
 
+int __must_check devm_init_work(struct device *dev, struct work_struct *work,
+					work_func_t func);
+int __must_check devm_init_delayed_work(struct device *dev,
+					struct delayed_work *dw,
+					work_func_t func);
+
 #endif
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index fc5d23d752a5..ab814b0b6c81 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5837,3 +5837,57 @@ int __init workqueue_init(void)
 
 	return 0;
 }
+
+static void devm_work_release(void *data)
+{
+	struct work_struct *work = data;
+
+	cancel_work_sync(work);
+}
+
+/**
+ * devm_init_work - resource-controlled version of INIT_WORK()
+ * @dev: valid struct device pointer
+ * @work: work pointer to initialize
+ * @func: work function to initialize 'work' with
+ *
+ * Initialize the work pointer just like INIT_WORK(), but use resource control
+ * to help ensure work is not left running or pending when dev is destroyed.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+int __must_check devm_init_work(struct device *dev, struct work_struct *work,
+					work_func_t func)
+{
+	INIT_WORK(work, func);
+	return devm_add_action(dev, devm_work_release, work);
+}
+EXPORT_SYMBOL_GPL(devm_init_work);
+
+static void devm_delayed_work_release(void *data)
+{
+	struct delayed_work *dw = data;
+
+	cancel_delayed_work_sync(dw);
+}
+
+/**
+ * devm_init_delayed_work - resource-controlled version of INIT_DELAYED_WORK()
+ * @dev: valid struct device pointer
+ * @dw: delayed_work pointer to initialize
+ * @func: work function to initialize 'dw' with
+ *
+ * Initialize the delayed_work pointer just like INIT_DELAYED_WORK(), but use
+ * resource control to help ensure delayed work is not left running or pending
+ * when dev is destroyed.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+int __must_check devm_init_delayed_work(struct device *dev,
+					struct delayed_work *dw,
+					work_func_t func)
+{
+	INIT_DELAYED_WORK(dw, func);
+	return devm_add_action(dev, devm_delayed_work_release, dw);
+}
+EXPORT_SYMBOL_GPL(devm_init_delayed_work);
-- 
2.17.1