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usb: gadget: udc: fix use-after-free in usb_gadget_state_work

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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 399a45e523 ("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: 5702f75375 ("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>
This commit is contained in:
Jimmy Hu
2025-10-23 05:49:45 +00:00
committed by Greg Kroah-Hartman
parent eb9ac77983
commit baeb66fbd4
2 changed files with 21 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
drivers/usb/gadget/udc/core.c
View File

@@ -1126,8 +1126,13 @@ 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);
trace_usb_gadget_set_state(gadget, 0);
}
EXPORT_SYMBOL_GPL(usb_gadget_set_state);
@@ -1361,6 +1366,8 @@ static void usb_udc_nop_release(struct device *dev)
void usb_initialize_gadget(struct device *parent, struct usb_gadget *gadget,
void (*release)(struct device *dev))
{
spin_lock_init(&gadget->state_lock);
gadget->teardown = false;
INIT_WORK(&gadget->work, usb_gadget_state_work);
gadget->dev.parent = parent;
@@ -1535,6 +1542,7 @@ EXPORT_SYMBOL_GPL(usb_add_gadget_udc);
void usb_del_gadget(struct usb_gadget *gadget)
{
struct usb_udc *udc = gadget->udc;
unsigned long flags;
if (!udc)
return;
@@ -1548,6 +1556,13 @@ void usb_del_gadget(struct usb_gadget *gadget)
kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE);
sysfs_remove_link(&udc->dev.kobj, "gadget");
device_del(&gadget->dev);
/*
* 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);
ida_free(&gadget_id_numbers, gadget->id_number);
cancel_work_sync(&udc->vbus_work);

5
include/linux/usb/gadget.h
View File

@@ -376,6 +376,9 @@ struct usb_gadget_ops {
* can handle. The UDC must support this and all slower speeds and lower
* number of lanes.
* @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.
@@ -451,6 +454,8 @@ struct usb_gadget {
enum usb_ssp_rate max_ssp_rate;
enum usb_device_state state;
spinlock_t state_lock;
bool teardown;
const char *name;
struct device dev;
unsigned isoch_delay;