usb: gadget: udc: core: Prevent soft_connect_store() race

usb_udc_connect_control(), soft_connect_store() and
usb_gadget_deactivate() can potentially race against each other to invoke
usb_gadget_connect()/usb_gadget_disconnect(). To prevent this, guard
udc->started, gadget->allow_connect, gadget->deactivate and
gadget->connect with connect_lock so that ->pullup() is only invoked when
the gadget is bound, started and not deactivated. The routines
usb_gadget_connect_locked(), usb_gadget_disconnect_locked(),
usb_udc_connect_control_locked(), usb_gadget_udc_start_locked(),
usb_gadget_udc_stop_locked() are called with this lock held.

An earlier version of this commit was reverted due to the crash reported in
https://lore.kernel.org/all/ZF4BvgsOyoKxdPFF@francesco-nb.int.toradex.com/.
commit 16737e78d190 ("usb: gadget: udc: core: Offload usb_udc_vbus_handler processing")
addresses the crash reported.

Cc: stable@vger.kernel.org
Fixes: 628ef0d273a6 ("usb: udc: add usb_udc_vbus_handler")
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Message-ID: <20230609010227.978661-2-badhri@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index d2e4f78..83fd1de 100644 (file)
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -40,6 +40,11 @@ static const struct bus_type gadget_bus_type;
  * @allow_connect: Indicates whether UDC is allowed to be pulled up.
  * Set/cleared by gadget_(un)bind_driver() after gadget driver is bound or
  * unbound.
+ * @connect_lock: protects udc->started, gadget->connect,
+ * gadget->allow_connect and gadget->deactivate. The routines
+ * usb_gadget_connect_locked(), usb_gadget_disconnect_locked(),
+ * usb_udc_connect_control_locked(), usb_gadget_udc_start_locked() and
+ * usb_gadget_udc_stop_locked() are called with this lock held.
  *
  * This represents the internal data structure which is used by the UDC-class
  * to hold information about udc driver and gadget together.
@@ -53,6 +58,7 @@ struct usb_udc {
        bool                            started;
        bool                            allow_connect;
        struct work_struct              vbus_work;
+       struct mutex                    connect_lock;
 };
 
 static struct class *udc_class;
@@ -692,17 +698,8 @@ out:
 }
 EXPORT_SYMBOL_GPL(usb_gadget_vbus_disconnect);
 
-/**
- * usb_gadget_connect - software-controlled connect to USB host
- * @gadget:the peripheral being connected
- *
- * Enables the D+ (or potentially D-) pullup.  The host will start
- * enumerating this gadget when the pullup is active and a VBUS session
- * is active (the link is powered).
- *
- * Returns zero on success, else negative errno.
- */
-int usb_gadget_connect(struct usb_gadget *gadget)
+static int usb_gadget_connect_locked(struct usb_gadget *gadget)
+       __must_hold(&gadget->udc->connect_lock)
 {
        int ret = 0;
 
@@ -711,10 +708,12 @@ int usb_gadget_connect(struct usb_gadget *gadget)
                goto out;
        }
 
-       if (gadget->deactivated || !gadget->udc->allow_connect) {
+       if (gadget->deactivated || !gadget->udc->allow_connect || !gadget->udc->started) {
                /*
-                * If gadget is deactivated we only save new state.
-                * Gadget will be connected automatically after activation.
+                * If the gadget isn't usable (because it is deactivated,
+                * unbound, or not yet started), we only save the new state.
+                * The gadget will be connected automatically when it is
+                * activated/bound/started.
                 */
                gadget->connected = true;
                goto out;
@@ -729,22 +728,31 @@ out:
 
        return ret;
 }
-EXPORT_SYMBOL_GPL(usb_gadget_connect);
 
 /**
- * usb_gadget_disconnect - software-controlled disconnect from USB host
- * @gadget:the peripheral being disconnected
- *
- * Disables the D+ (or potentially D-) pullup, which the host may see
- * as a disconnect (when a VBUS session is active).  Not all systems
- * support software pullup controls.
+ * usb_gadget_connect - software-controlled connect to USB host
+ * @gadget:the peripheral being connected
  *
- * Following a successful disconnect, invoke the ->disconnect() callback
- * for the current gadget driver so that UDC drivers don't need to.
+ * Enables the D+ (or potentially D-) pullup.  The host will start
+ * enumerating this gadget when the pullup is active and a VBUS session
+ * is active (the link is powered).
  *
  * Returns zero on success, else negative errno.
  */
-int usb_gadget_disconnect(struct usb_gadget *gadget)
+int usb_gadget_connect(struct usb_gadget *gadget)
+{
+       int ret;
+
+       mutex_lock(&gadget->udc->connect_lock);
+       ret = usb_gadget_connect_locked(gadget);
+       mutex_unlock(&gadget->udc->connect_lock);
+
+       return ret;
+}
+EXPORT_SYMBOL_GPL(usb_gadget_connect);
+
+static int usb_gadget_disconnect_locked(struct usb_gadget *gadget)
+       __must_hold(&gadget->udc->connect_lock)
 {
        int ret = 0;
 
@@ -756,7 +764,7 @@ int usb_gadget_disconnect(struct usb_gadget *gadget)
        if (!gadget->connected)
                goto out;
 
-       if (gadget->deactivated) {
+       if (gadget->deactivated || !gadget->udc->started) {
                /*
                 * If gadget is deactivated we only save new state.
                 * Gadget will stay disconnected after activation.
@@ -779,6 +787,30 @@ out:
 
        return ret;
 }
+
+/**
+ * usb_gadget_disconnect - software-controlled disconnect from USB host
+ * @gadget:the peripheral being disconnected
+ *
+ * Disables the D+ (or potentially D-) pullup, which the host may see
+ * as a disconnect (when a VBUS session is active).  Not all systems
+ * support software pullup controls.
+ *
+ * Following a successful disconnect, invoke the ->disconnect() callback
+ * for the current gadget driver so that UDC drivers don't need to.
+ *
+ * Returns zero on success, else negative errno.
+ */
+int usb_gadget_disconnect(struct usb_gadget *gadget)
+{
+       int ret;
+
+       mutex_lock(&gadget->udc->connect_lock);
+       ret = usb_gadget_disconnect_locked(gadget);
+       mutex_unlock(&gadget->udc->connect_lock);
+
+       return ret;
+}
 EXPORT_SYMBOL_GPL(usb_gadget_disconnect);
 
 /**
@@ -796,13 +828,14 @@ int usb_gadget_deactivate(struct usb_gadget *gadget)
 {
        int ret = 0;
 
+       mutex_lock(&gadget->udc->connect_lock);
        if (gadget->deactivated)
-               goto out;
+               goto unlock;
 
        if (gadget->connected) {
-               ret = usb_gadget_disconnect(gadget);
+               ret = usb_gadget_disconnect_locked(gadget);
                if (ret)
-                       goto out;
+                       goto unlock;
 
                /*
                 * If gadget was being connected before deactivation, we want
@@ -812,7 +845,8 @@ int usb_gadget_deactivate(struct usb_gadget *gadget)
        }
        gadget->deactivated = true;
 
-out:
+unlock:
+       mutex_unlock(&gadget->udc->connect_lock);
        trace_usb_gadget_deactivate(gadget, ret);
 
        return ret;
@@ -832,8 +866,9 @@ int usb_gadget_activate(struct usb_gadget *gadget)
 {
        int ret = 0;
 
+       mutex_lock(&gadget->udc->connect_lock);
        if (!gadget->deactivated)
-               goto out;
+               goto unlock;
 
        gadget->deactivated = false;
 
@@ -842,9 +877,11 @@ int usb_gadget_activate(struct usb_gadget *gadget)
         * while it was being deactivated, we call usb_gadget_connect().
         */
        if (gadget->connected)
-               ret = usb_gadget_connect(gadget);
+               ret = usb_gadget_connect_locked(gadget);
+       mutex_unlock(&gadget->udc->connect_lock);
 
-out:
+unlock:
+       mutex_unlock(&gadget->udc->connect_lock);
        trace_usb_gadget_activate(gadget, ret);
 
        return ret;
@@ -1083,19 +1120,22 @@ EXPORT_SYMBOL_GPL(usb_gadget_set_state);
 
 /* ------------------------------------------------------------------------- */
 
-static void usb_udc_connect_control(struct usb_udc *udc)
+/* Acquire connect_lock before calling this function. */
+static void usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc->connect_lock)
 {
        if (udc->vbus)
-               usb_gadget_connect(udc->gadget);
+               usb_gadget_connect_locked(udc->gadget);
        else
-               usb_gadget_disconnect(udc->gadget);
+               usb_gadget_disconnect_locked(udc->gadget);
 }
 
 static void vbus_event_work(struct work_struct *work)
 {
        struct usb_udc *udc = container_of(work, struct usb_udc, vbus_work);
 
-       usb_udc_connect_control(udc);
+       mutex_lock(&udc->connect_lock);
+       usb_udc_connect_control_locked(udc);
+       mutex_unlock(&udc->connect_lock);
 }
 
 /**
@@ -1144,7 +1184,7 @@ void usb_gadget_udc_reset(struct usb_gadget *gadget,
 EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);
 
 /**
- * usb_gadget_udc_start - tells usb device controller to start up
+ * usb_gadget_udc_start_locked - tells usb device controller to start up
  * @udc: The UDC to be started
  *
  * This call is issued by the UDC Class driver when it's about
@@ -1155,8 +1195,11 @@ EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);
  * necessary to have it powered on.
  *
  * Returns zero on success, else negative errno.
+ *
+ * Caller should acquire connect_lock before invoking this function.
  */
-static inline int usb_gadget_udc_start(struct usb_udc *udc)
+static inline int usb_gadget_udc_start_locked(struct usb_udc *udc)
+       __must_hold(&udc->connect_lock)
 {
        int ret;
 
@@ -1173,7 +1216,7 @@ static inline int usb_gadget_udc_start(struct usb_udc *udc)
 }
 
 /**
- * usb_gadget_udc_stop - tells usb device controller we don't need it anymore
+ * usb_gadget_udc_stop_locked - tells usb device controller we don't need it anymore
  * @udc: The UDC to be stopped
  *
  * This call is issued by the UDC Class driver after calling
@@ -1182,8 +1225,11 @@ static inline int usb_gadget_udc_start(struct usb_udc *udc)
  * The details are implementation specific, but it can go as
  * far as powering off UDC completely and disable its data
  * line pullups.
+ *
+ * Caller should acquire connect lock before invoking this function.
  */
-static inline void usb_gadget_udc_stop(struct usb_udc *udc)
+static inline void usb_gadget_udc_stop_locked(struct usb_udc *udc)
+       __must_hold(&udc->connect_lock)
 {
        if (!udc->started) {
                dev_err(&udc->dev, "UDC had already stopped\n");
@@ -1342,6 +1388,7 @@ int usb_add_gadget(struct usb_gadget *gadget)
 
        udc->gadget = gadget;
        gadget->udc = udc;
+       mutex_init(&udc->connect_lock);
 
        udc->started = false;
 
@@ -1545,12 +1592,16 @@ static int gadget_bind_driver(struct device *dev)
        if (ret)
                goto err_bind;
 
-       ret = usb_gadget_udc_start(udc);
-       if (ret)
+       mutex_lock(&udc->connect_lock);
+       ret = usb_gadget_udc_start_locked(udc);
+       if (ret) {
+               mutex_unlock(&udc->connect_lock);
                goto err_start;
+       }
        usb_gadget_enable_async_callbacks(udc);
        udc->allow_connect = true;
-       usb_udc_connect_control(udc);
+       usb_udc_connect_control_locked(udc);
+       mutex_unlock(&udc->connect_lock);
 
        kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
        return 0;
@@ -1583,12 +1634,14 @@ static void gadget_unbind_driver(struct device *dev)
 
        udc->allow_connect = false;
        cancel_work_sync(&udc->vbus_work);
-       usb_gadget_disconnect(gadget);
+       mutex_lock(&udc->connect_lock);
+       usb_gadget_disconnect_locked(gadget);
        usb_gadget_disable_async_callbacks(udc);
        if (gadget->irq)
                synchronize_irq(gadget->irq);
        udc->driver->unbind(gadget);
-       usb_gadget_udc_stop(udc);
+       usb_gadget_udc_stop_locked(udc);
+       mutex_unlock(&udc->connect_lock);
 
        mutex_lock(&udc_lock);
        driver->is_bound = false;
@@ -1674,11 +1727,15 @@ static ssize_t soft_connect_store(struct device *dev,
        }
 
        if (sysfs_streq(buf, "connect")) {
-               usb_gadget_udc_start(udc);
-               usb_gadget_connect(udc->gadget);
+               mutex_lock(&udc->connect_lock);
+               usb_gadget_udc_start_locked(udc);
+               usb_gadget_connect_locked(udc->gadget);
+               mutex_unlock(&udc->connect_lock);
        } else if (sysfs_streq(buf, "disconnect")) {
-               usb_gadget_disconnect(udc->gadget);
-               usb_gadget_udc_stop(udc);
+               mutex_lock(&udc->connect_lock);
+               usb_gadget_disconnect_locked(udc->gadget);
+               usb_gadget_udc_stop_locked(udc);
+               mutex_unlock(&udc->connect_lock);
        } else {
                dev_err(dev, "unsupported command '%s'\n", buf);
                ret = -EINVAL;