linux-kernel - [PATCH v5] driver core: enforce device_lock for driver_match

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Message-ID: <20260113162843.12712-1-hanguidong02@gmail.com>
Date: Wed, 14 Jan 2026 00:28:43 +0800
From: Gui-Dong Han <hanguidong02@...il.com>
To: gregkh@...uxfoundation.org,
	rafael@...nel.org,
	dakr@...nel.org
Cc: linux-kernel@...r.kernel.org,
	baijiaju1990@...il.com,
	Gui-Dong Han <hanguidong02@...il.com>,
	Qiu-ji Chen <chenqiuji666@...il.com>
Subject: [PATCH v5] driver core: enforce device_lock for driver_match_device()

Currently, driver_match_device() is called from three sites. One site
(__device_attach_driver) holds device_lock(dev), but the other two
(bind_store and __driver_attach) do not. This inconsistency means that
bus match() callbacks are not guaranteed to be called with the lock
held.

Fix this by introducing driver_match_device_locked(), which guarantees
holding the device lock using a scoped guard. Replace the unlocked calls
in bind_store() and __driver_attach() with this new helper. Also add a
lock assertion to driver_match_device() to enforce this guarantee.

This consistency also fixes a known race condition. The driver_override
implementation relies on the device_lock, so the missing lock led to the
use-after-free (UAF) reported in Bugzilla for buses using this field.

Stress testing the two newly locked paths for 24 hours with
CONFIG_PROVE_LOCKING and CONFIG_LOCKDEP enabled showed no UAF recurrence
and no lockdep warnings.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
Suggested-by: Qiu-ji Chen <chenqiuji666@...il.com>
Signed-off-by: Gui-Dong Han <hanguidong02@...il.com>
---
v5:
* Introduce driver_match_device_locked() helper using guard(device) to
handle locking, as suggested by Rafael J. Wysocki.
v4:
* Remove the misleading comment above device_lock_assert(), and update
subject and commit message to focus on enforcing consistent locking,
as discussed with Danilo Krummrich.
v3:
* Remove redundant locking comments at call sites and add a blank line
after the lock assertion in driver_match_device(), as suggested by Greg KH.
v2:
* Add device_lock_assert() in driver_match_device() to enforce locking
requirement, as suggested by Greg KH.
v1:
* The Bugzilla entry contains full KASAN reports and two PoCs that reliably
reproduce the UAF on both unlocked paths using a standard QEMU setup
(default e1000 device at 0000:00:03.0).
---
 drivers/base/base.h | 9 +++++++++
 drivers/base/bus.c  | 2 +-
 drivers/base/dd.c   | 2 +-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 430cbefbc97f..677320881af1 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -182,9 +182,18 @@ void device_set_deferred_probe_reason(const struct device *dev, struct va_format
 static inline int driver_match_device(const struct device_driver *drv,
 				      struct device *dev)
 {
+	device_lock_assert(dev);
+
 	return drv->bus->match ? drv->bus->match(dev, drv) : 1;
 }
 
+static inline int driver_match_device_locked(const struct device_driver *drv,
+					     struct device *dev)
+{
+	guard(device)(dev);
+	return driver_match_device(drv, dev);
+}
+
 static inline void dev_sync_state(struct device *dev)
 {
 	if (dev->bus->sync_state)
diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 9eb7771706f0..331d750465e2 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -263,7 +263,7 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf,
 	int err = -ENODEV;
 
 	dev = bus_find_device_by_name(bus, NULL, buf);
-	if (dev && driver_match_device(drv, dev)) {
+	if (dev && driver_match_device_locked(drv, dev)) {
 		err = device_driver_attach(drv, dev);
 		if (!err) {
 			/* success */
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 349f31bedfa1..98feb4c77160 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -1178,7 +1178,7 @@ static int __driver_attach(struct device *dev, void *data)
 	 * is an error.
 	 */
 
-	ret = driver_match_device(drv, dev);
+	ret = driver_match_device_locked(drv, dev);
 	if (ret == 0) {
 		/* no match */
 		return 0;
-- 
2.43.0