FAILED: patch "[PATCH] usb: gadget: udc: fix use-after-free in usb_gadget_state_work" failed to apply to 6.12-stable tree

PATCH New [email protected] 2 participants 3 messages Dec 1, 2025 – Dec 2, 2025

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[email protected]

author maintainer

2025-12-01 17:11 UTC #0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x baeb66fbd4201d1c4325074e78b1f557dff89b5b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025120121-sift-shiny-dd51@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From baeb66fbd4201d1c4325074e78b1f557dff89b5b Mon Sep 17 00:00:00 2001
From: Jimmy Hu <[email protected]>
Date: Thu, 23 Oct 2025 05:49:45 +0000
Subject: [PATCH] usb: gadget: udc: fix use-after-free in usb_gadget_state_work

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 <[email protected]>

Signed-off-by Jimmy Hu <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Greg Kroah-Hartman <[email protected]>

drivers/usb/gadget/udc/core.c +16 -1

index 694653761c44..8dbe79bdc0f9 100644
@@ -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);

include/linux/usb/gadget.h +5 -0

index 3aaf19e77558..8285b19a25e0 100644
@@ -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;

Sasha Levin

maintainer

2025-12-02 01:52 UTC #1 lore raw

PATCH 1/2 usb: udc: Add trace event for usb_gadget_set_state

From: Kuen-Han Tsai <[email protected]>

[ Upstream commit 7bf1158514e410310aec975e630cec99d4e4092f ]

While the userspace program can be notified of gadget state changes, timing issue can lead to missed transitions when reading the state value.

Introduce a trace event for usb_gadget_set_state to reliably track state transitions.

Signed-off-by Kuen-Han Tsai <[email protected]>

Link https://lore.kernel.org/r/[email protected] open here

Signed-off-by Greg Kroah-Hartman <[email protected]>

Stable-dep-of: baeb66fbd420 ("usb: gadget: udc: fix use-after-free in usb_gadget_state_work")

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/usb/gadget/udc/core.c  | 1 +
 drivers/usb/gadget/udc/trace.h | 5 +++++
 2 files changed, 6 insertions(+)

drivers/usb/gadget/udc/core.c +1 -0

index e3d63b8fa0f4c..694653761c44c 100644
@@ -1128,6 +1128,7 @@ void usb_gadget_set_state(struct usb_gadget *gadget,
 {
 	gadget->state = state;
 	schedule_work(&gadget->work);
+	trace_usb_gadget_set_state(gadget, 0);
 }
 EXPORT_SYMBOL_GPL(usb_gadget_set_state);

drivers/usb/gadget/udc/trace.h +5 -0

index 4e334298b0e8a..fa3e6ddf0a128 100644
@@ -81,6 +81,11 @@ DECLARE_EVENT_CLASS(udc_log_gadget,
 		__entry->ret)
 );
 
+DEFINE_EVENT(udc_log_gadget, usb_gadget_set_state,
+	TP_PROTO(struct usb_gadget *g, int ret),
+	TP_ARGS(g, ret)
+);
+
 DEFINE_EVENT(udc_log_gadget, usb_gadget_frame_number,
 	TP_PROTO(struct usb_gadget *g, int ret),
 	TP_ARGS(g, ret)

Signature · 1 line

2.51.0

Sasha Levin

maintainer

2025-12-02 01:52 UTC #2 lore raw

PATCH 2/2 usb: gadget: udc: fix use-after-free in usb_gadget_state_work

From: Jimmy Hu <[email protected]>

[ 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().

Fixes 5702f75375aa9 ("usb: gadget: udc-core: move sysfs_notify() to a workqueue")

Cc stable <[email protected]>

Signed-off-by Jimmy Hu <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Greg Kroah-Hartman <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/usb/gadget/udc/core.c | 17 ++++++++++++++++-
 include/linux/usb/gadget.h    |  5 +++++
 2 files changed, 21 insertions(+), 1 deletion(-)

drivers/usb/gadget/udc/core.c +16 -1

index 694653761c44c..8dbe79bdc0f9c 100644
@@ -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);

include/linux/usb/gadget.h +5 -0

index da4309f3cea3f..b5d9a1d91e39e 100644
@@ -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;

Signature · 1 line

2.51.0