bus: fsl-mc: fix use-after-free in driver_override_show()

commit 148891e95014b5dc5878acefa57f1940c281c431 upstream.

The driver_override_show() function reads the driver_override string
without holding the device_lock. However, driver_override_store() uses
driver_set_override(), which modifies and frees the string while holding
the device_lock.

This can result in a concurrent use-after-free if the string is freed
by the store function while being read by the show function.

Fix this by holding the device_lock around the read operation.

Fixes: 1f86a00c1159 ("bus/fsl-mc: add support for 'driver_override' in the mc-bus")
Cc: stable@vger.kernel.org
Signed-off-by: Gui-Dong Han <hanguidong02@gmail.com>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20251202174438.12658-1-hanguidong02@gmail.com
Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index 25845c04e5620aff54a33c26a08170f6f3a88720..a97baf2cbcdd515e4a85357b0d0083cd2397ad8c 100644 (file)
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
@@ -202,8 +202,12 @@ static ssize_t driver_override_show(struct device *dev,
                                    struct device_attribute *attr, char *buf)
 {
        struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
+       ssize_t len;
 
-       return sysfs_emit(buf, "%s\n", mc_dev->driver_override);
+       device_lock(dev);
+       len = sysfs_emit(buf, "%s\n", mc_dev->driver_override);
+       device_unlock(dev);
+       return len;
 }
 static DEVICE_ATTR_RW(driver_override);