[PATCH 6.1 0581/1191] USB: make single lock for all usb dynamic id lists

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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2026-09-12 16:09:54
Also in: linux-patches, stable
Subsystem: the rest, usb serial subsystem, usb subsystem · Maintainers: Linus Torvalds, Johan Hovold, Greg Kroah-Hartman

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

[ Upstream commit 0b3144da31f855fce652303f588416a60991bdef ]

There are a number of places where we accidentally pass in a constant
structure to later cast it off to a dynamic one, and then attempt to
grab a lock on it, which is not a good idea.  To help resolve this, move
the dynamic id lock out of the dynamic id structure for the driver and
into one single lock for all USB dynamic ids.  As this lock should never
have any real contention (it's only every accessed when a device is
added or removed, which is always serialized) there should not be any
difference except for some memory savings.

Note, this just converts the existing use of the dynamic id lock to the
new static lock, there is one place that is accessing the dynamic id
list without grabbing the lock, that will be fixed up in a follow-on
change.

Cc: Johan Hovold <johan@kernel.org>
Cc: Herve Codina <herve.codina@bootlin.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Grant Grundler <redacted>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Yajun Deng <redacted>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: <redacted>
Link: https://lore.kernel.org/r/2024111322-kindly-finalist-d247@gregkh (local)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: ef8154d8b52d ("usb: fix UAF when probe runs concurrent to dyn ID removal")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/usb/common/common.c     |  3 +++
 drivers/usb/core/driver.c       | 15 +++++----------
 drivers/usb/serial/bus.c        |  4 +---
 drivers/usb/serial/usb-serial.c |  4 +---
 include/linux/usb.h             |  2 +-
 5 files changed, 11 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/common/common.c b/drivers/usb/common/common.c
index c9bdeb4ddcb57..495b8114ed8f3 100644
--- a/drivers/usb/common/common.c
+++ b/drivers/usb/common/common.c

@@ -416,6 +416,9 @@ EXPORT_SYMBOL_GPL(usb_of_get_companion_dev);
 struct dentry *usb_debug_root;
 EXPORT_SYMBOL_GPL(usb_debug_root);
 
+DEFINE_MUTEX(usb_dynids_lock);
+EXPORT_SYMBOL_GPL(usb_dynids_lock);
+
 static int __init usb_common_init(void)
 {
 	usb_debug_root = debugfs_create_dir("usb", NULL);

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 698ca073097c7..e875723ddef26 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c

@@ -95,9 +95,9 @@ ssize_t usb_store_new_id(struct usb_dynids *dynids,
 		}
 	}
 
-	spin_lock(&dynids->lock);
+	mutex_lock(&usb_dynids_lock);
 	list_add_tail(&dynid->node, &dynids->list);
-	spin_unlock(&dynids->lock);
+	mutex_unlock(&usb_dynids_lock);
 
 	retval = driver_attach(driver);

@@ -160,7 +160,7 @@ static ssize_t remove_id_store(struct device_driver *driver, const char *buf,
 	if (fields < 2)
 		return -EINVAL;
 
-	spin_lock(&usb_driver->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry_safe(dynid, n, &usb_driver->dynids.list, node) {
 		struct usb_device_id *id = &dynid->id;

@@ -171,7 +171,6 @@ static ssize_t remove_id_store(struct device_driver *driver, const char *buf,
 			break;
 		}
 	}
-	spin_unlock(&usb_driver->dynids.lock);
 	return count;
 }

@@ -220,12 +219,11 @@ static void usb_free_dynids(struct usb_driver *usb_drv)
 {
 	struct usb_dynid *dynid, *n;
 
-	spin_lock(&usb_drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry_safe(dynid, n, &usb_drv->dynids.list, node) {
 		list_del(&dynid->node);
 		kfree(dynid);
 	}
-	spin_unlock(&usb_drv->dynids.lock);
 }
 
 static const struct usb_device_id *usb_match_dynamic_id(struct usb_interface *intf,

@@ -233,14 +231,12 @@ static const struct usb_device_id *usb_match_dynamic_id(struct usb_interface *in
 {
 	struct usb_dynid *dynid;
 
-	spin_lock(&drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry(dynid, &drv->dynids.list, node) {
 		if (usb_match_one_id(intf, &dynid->id)) {
-			spin_unlock(&drv->dynids.lock);
 			return &dynid->id;
 		}
 	}
-	spin_unlock(&drv->dynids.lock);
 	return NULL;
 }

@@ -1059,7 +1055,6 @@ int usb_register_driver(struct usb_driver *new_driver, struct module *owner,
 	new_driver->driver.owner = owner;
 	new_driver->driver.mod_name = mod_name;
 	new_driver->driver.dev_groups = new_driver->dev_groups;
-	spin_lock_init(&new_driver->dynids.lock);
 	INIT_LIST_HEAD(&new_driver->dynids.list);
 
 	retval = driver_register(&new_driver->driver);

diff --git a/drivers/usb/serial/bus.c b/drivers/usb/serial/bus.c
index 2efb9244d7055..25027ee64eae4 100644
--- a/drivers/usb/serial/bus.c
+++ b/drivers/usb/serial/bus.c

@@ -136,12 +136,11 @@ static void free_dynids(struct usb_serial_driver *drv)
 {
 	struct usb_dynid *dynid, *n;
 
-	spin_lock(&drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry_safe(dynid, n, &drv->dynids.list, node) {
 		list_del(&dynid->node);
 		kfree(dynid);
 	}
-	spin_unlock(&drv->dynids.lock);
 }
 
 struct bus_type usb_serial_bus_type = {

@@ -157,7 +156,6 @@ int usb_serial_bus_register(struct usb_serial_driver *driver)
 	int retval;
 
 	driver->driver.bus = &usb_serial_bus_type;
-	spin_lock_init(&driver->dynids.lock);
 	INIT_LIST_HEAD(&driver->dynids.list);
 
 	retval = driver_register(&driver->driver);

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index adfcecccd99ca..fa01320aaf143 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c

@@ -707,14 +707,12 @@ static const struct usb_device_id *match_dynamic_id(struct usb_interface *intf,
 {
 	struct usb_dynid *dynid;
 
-	spin_lock(&drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry(dynid, &drv->dynids.list, node) {
 		if (usb_match_one_id(intf, &dynid->id)) {
-			spin_unlock(&drv->dynids.lock);
 			return &dynid->id;
 		}
 	}
-	spin_unlock(&drv->dynids.lock);
 	return NULL;
 }

diff --git a/include/linux/usb.h b/include/linux/usb.h
index 3a29ed21a9375..660a8b2c8338e 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h

@@ -1097,8 +1097,8 @@ static inline int usb_make_path(struct usb_device *dev, char *buf, size_t size)
 /* ----------------------------------------------------------------------- */
 
 /* Stuff for dynamic usb ids */
+extern struct mutex usb_dynids_lock;
 struct usb_dynids {
-	spinlock_t lock;
 	struct list_head list;
 };

-- 
2.53.0

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