From: Jimmy Hu hhhuuu@google.com
[ Upstream commit baeb66fbd4201d1c4325074e78b1f557dff89b5b ]
A race condition during gadget teardown can lead to a use-after-free in usb_gadget_state_work(), as reported by KASAN:
BUG: KASAN: invalid-access in sysfs_notify+0x2c/0xd0 Workqueue: events usb_gadget_state_work
The fundamental race occurs because a concurrent event (e.g., an interrupt) can call usb_gadget_set_state() and schedule gadget->work at any time during the cleanup process in usb_del_gadget().
Commit 399a45e5237c ("usb: gadget: core: flush gadget workqueue after device removal") attempted to fix this by moving flush_work() to after device_del(). However, this does not fully solve the race, as a new work item can still be scheduled *after* flush_work() completes but before the gadget's memory is freed, leading to the same use-after-free.
This patch fixes the race condition robustly by introducing a 'teardown' flag and a 'state_lock' spinlock to the usb_gadget struct. The flag is set during cleanup in usb_del_gadget() *before* calling flush_work() to prevent any new work from being scheduled once cleanup has commenced. The scheduling site, usb_gadget_set_state(), now checks this flag under the lock before queueing the work, thus safely closing the race window.
Fixes: 5702f75375aa9 ("usb: gadget: udc-core: move sysfs_notify() to a workqueue") Cc: stable stable@kernel.org Signed-off-by: Jimmy Hu hhhuuu@google.com Link: https://patch.msgid.link/20251023054945.233861-1-hhhuuu@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [ Adjust context ] Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/usb/gadget/udc/core.c | 17 ++++++++++++++++- include/linux/usb/gadget.h | 5 +++++ 2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c index dd2fafc5b0c3e..598053bf985db 100644 --- a/drivers/usb/gadget/udc/core.c +++ b/drivers/usb/gadget/udc/core.c @@ -1037,8 +1037,13 @@ static void usb_gadget_state_work(struct work_struct *work) void usb_gadget_set_state(struct usb_gadget *gadget, enum usb_device_state state) { + unsigned long flags; + + spin_lock_irqsave(&gadget->state_lock, flags); gadget->state = state; - schedule_work(&gadget->work); + if (!gadget->teardown) + schedule_work(&gadget->work); + spin_unlock_irqrestore(&gadget->state_lock, flags); } EXPORT_SYMBOL_GPL(usb_gadget_set_state);
@@ -1199,6 +1204,8 @@ void usb_initialize_gadget(struct device *parent, struct usb_gadget *gadget, void (*release)(struct device *dev)) { dev_set_name(&gadget->dev, "gadget"); + spin_lock_init(&gadget->state_lock); + gadget->teardown = false; INIT_WORK(&gadget->work, usb_gadget_state_work); gadget->dev.parent = parent;
@@ -1376,6 +1383,7 @@ static void usb_gadget_remove_driver(struct usb_udc *udc) void usb_del_gadget(struct usb_gadget *gadget) { struct usb_udc *udc = gadget->udc; + unsigned long flags;
if (!udc) return; @@ -1394,6 +1402,13 @@ void usb_del_gadget(struct usb_gadget *gadget) mutex_unlock(&udc_lock);
kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE); + /* + * Set the teardown flag before flushing the work to prevent new work + * from being scheduled while we are cleaning up. + */ + spin_lock_irqsave(&gadget->state_lock, flags); + gadget->teardown = true; + spin_unlock_irqrestore(&gadget->state_lock, flags); flush_work(&gadget->work); device_unregister(&udc->dev); device_del(&gadget->dev); diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h index 11df3d5b40c6b..8bdeced70a339 100644 --- a/include/linux/usb/gadget.h +++ b/include/linux/usb/gadget.h @@ -341,6 +341,9 @@ struct usb_gadget_ops { * @max_speed: Maximal speed the UDC can handle. UDC must support this * and all slower speeds. * @state: the state we are now (attached, suspended, configured, etc) + * @state_lock: Spinlock protecting the `state` and `teardown` members. + * @teardown: True if the device is undergoing teardown, used to prevent + * new work from being scheduled during cleanup. * @name: Identifies the controller hardware type. Used in diagnostics * and sometimes configuration. * @dev: Driver model state for this abstract device. @@ -408,6 +411,8 @@ struct usb_gadget { enum usb_device_speed speed; enum usb_device_speed max_speed; enum usb_device_state state; + spinlock_t state_lock; + bool teardown; const char *name; struct device dev; unsigned isoch_delay;