[PATCH v4] driver core: enforce device_lock for driver_match_device()

[Gui-Dong Han <hanguidong02@gmail.com>]

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 holding device_lock(dev) around the driver_match_device()
calls in bind_store() and __driver_attach(). This ensures consistent
locking for all match() callbacks. 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@gmail.com>
Signed-off-by: Gui-Dong Han <hanguidong02@gmail.com>
---
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 |  2 ++
 drivers/base/bus.c  | 16 +++++++++++-----
 drivers/base/dd.c   |  2 ++
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 430cbefbc97f..aa701878c6e3 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -182,6 +182,8 @@ 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;
 }
 
diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 9eb7771706f0..5cbcf9f5bd6e 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -261,13 +261,19 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf,
 	const struct bus_type *bus = bus_get(drv->bus);
 	struct device *dev;
 	int err = -ENODEV;
+	int ret;
 
 	dev = bus_find_device_by_name(bus, NULL, buf);
-	if (dev && driver_match_device(drv, dev)) {
-		err = device_driver_attach(drv, dev);
-		if (!err) {
-			/* success */
-			err = count;
+	if (dev) {
+		device_lock(dev);
+		ret = driver_match_device(drv, dev);
+		device_unlock(dev);
+		if (ret) {
+			err = device_driver_attach(drv, dev);
+			if (!err) {
+				/* success */
+				err = count;
+			}
 		}
 	}
 	put_device(dev);
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 349f31bedfa1..e79c732a56e4 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -1178,7 +1178,9 @@ static int __driver_attach(struct device *dev, void *data)
 	 * is an error.
 	 */
 
+	device_lock(dev);
 	ret = driver_match_device(drv, dev);
+	device_unlock(dev);
 	if (ret == 0) {
 		/* no match */
 		return 0;
-- 
2.43.0