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[75.221.107.128]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-bd75def6314sm18969714a12.7.2025.11.26.03.30.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Nov 2025 03:30:35 -0800 (PST) From: Gui-Dong Han To: gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org Cc: linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, Gui-Dong Han , Qiu-ji Chen Subject: [PATCH] driver core: fix use-after-free of driver_override via driver_match_device() Date: Wed, 26 Nov 2025 19:30:06 +0800 Message-ID: <20251126113006.9925-1-hanguidong02@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" driver_set_override() modifies and frees dev->driver_override while holding device_lock(dev). However, driver_match_device() reads dev->driver_override when calling bus match functions. 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 allows a concurrent driver_set_override() to free the string while driver_match_device() is using it, leading to a use-after-free (UAF). This issue affects at least 11 bus types (including PCI, AMBA, Platform) that rely on driver_override for matching. Fix this by holding device_lock(dev) around the driver_match_device() calls in bind_store() and __driver_attach(). This ensures all access to dev->driver_override via driver_match_device() is protected by the device lock. Tested with the PoCs from Bugzilla that trigger this UAF. 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=3D220789 Suggested-by: Qiu-ji Chen Signed-off-by: Gui-Dong Han --- 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). I chose to fix this in the driver core for the following reasons: 1. Both racing functions are part of the driver core. 2. Fixing this per-driver/per-bus is tedious and would require careful ad-hoc locking that does not align with the existing device_lock(dev). 3. We cannot simply add device_lock(dev) inside bus match functions because one call path (__device_attach_driver) already holds this lock. Adding the lock inside the match callback would cause a deadlock on that path. --- drivers/base/bus.c | 17 ++++++++++++----- drivers/base/dd.c | 3 +++ 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/drivers/base/bus.c b/drivers/base/bus.c index 5e75e1bce551..9e62d6009058 100644 --- a/drivers/base/bus.c +++ b/drivers/base/bus.c @@ -261,13 +261,20 @@ static ssize_t bind_store(struct device_driver *drv, = const char *buf, const struct bus_type *bus =3D bus_get(drv->bus); struct device *dev; int err =3D -ENODEV; + int ret; =20 dev =3D bus_find_device_by_name(bus, NULL, buf); - if (dev && driver_match_device(drv, dev)) { - err =3D device_driver_attach(drv, dev); - if (!err) { - /* success */ - err =3D count; + if (dev) { + /* Protects against driver_set_override() races */ + device_lock(dev); + ret =3D driver_match_device(drv, dev); + device_unlock(dev); + if (ret) { + err =3D device_driver_attach(drv, dev); + if (!err) { + /* success */ + err =3D count; + } } } put_device(dev); diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 13ab98e033ea..db60b4500136 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -1170,7 +1170,10 @@ static int __driver_attach(struct device *dev, void = *data) * is an error. */ =20 + /* Protects against driver_set_override() races */ + device_lock(dev); ret =3D driver_match_device(drv, dev); + device_unlock(dev); if (ret =3D=3D 0) { /* no match */ return 0; --=20 2.43.0