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usb: gadget: udc: core: Prevent soft_connect_store() race
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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: 628ef0d ("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>
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Badhri Jagan Sridharan authored and Greg Kroah-Hartman committed Jun 13, 2023
1 parent 50966da commit 286d997
Showing 1 changed file with 106 additions and 49 deletions.
155 changes: 106 additions & 49 deletions drivers/usb/gadget/udc/core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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.
Expand All @@ -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;
Expand Down Expand Up @@ -692,17 +698,8 @@ int usb_gadget_vbus_disconnect(struct usb_gadget *gadget)
}
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;

Expand All @@ -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;
Expand All @@ -729,22 +728,31 @@ int usb_gadget_connect(struct usb_gadget *gadget)

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;

Expand All @@ -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.
Expand All @@ -779,6 +787,30 @@ int usb_gadget_disconnect(struct usb_gadget *gadget)

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);

/**
Expand All @@ -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
Expand All @@ -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;
Expand All @@ -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;

Expand All @@ -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;
Expand Down Expand Up @@ -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);
}

/**
Expand Down Expand Up @@ -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
Expand All @@ -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;

Expand All @@ -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
Expand All @@ -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");
Expand Down Expand Up @@ -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;

Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down

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