[PATCH] driver core: fix potential null-ptr-deref in device_add()

[Yang Yingliang]

I got the following null-ptr-deref report while doing fault injection test:

BUG: kernel NULL pointer dereference, address: 0000000000000058
CPU: 2 PID: 278 Comm: 37-i2c-ds2482 Tainted: G    B   W        N 6.1.0-rc3+
RIP: 0010:klist_put+0x2d/0xd0
Call Trace:
 <TASK>
 klist_remove+0xf1/0x1c0
 device_release_driver_internal+0x196/0x210
 bus_remove_device+0x1bd/0x240
 device_add+0xd3d/0x1100
 w1_add_master_device+0x476/0x490 [wire]
 ds2482_probe+0x303/0x3e0 [ds2482]

This is how it happened:

w1_alloc_dev()
  // The dev->driver is set to w1_master_driver.
  memcpy(&dev->dev, device, sizeof(struct device));
  device_add()
    bus_add_device()
    dpm_sysfs_add() // It fails, calls bus_remove_device.

    // error path
    bus_remove_device()
      // The dev->driver is not null, but driver is not bound.
      __device_release_driver()
        klist_remove(&dev->p->knode_driver) <-- It causes null-ptr-deref.

    // normal path
    bus_probe_device() // It's not called yet.
      device_bind_driver()

If dev->driver is set, in the error path after calling bus_add_device()
in device_add(), bus_remove_device() is called, then the device will be
detached from driver. But device_bind_driver() is not called yet, so it
causes null-ptr-deref while access the 'knode_driver'. To fix this, set
dev->driver to null in the error path before calling bus_remove_device().

Fixes: 57eee3d23e88 ("Driver core: Call device_pm_add() after bus_add_device() in device_add()")
Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
---
 drivers/base/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index d02501933467..e5c15061070b 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3551,6 +3551,7 @@ int device_add(struct device *dev)
 	device_pm_remove(dev);
 	dpm_sysfs_remove(dev);
  DPMError:
+	dev->driver = NULL;
 	bus_remove_device(dev);
  BusError:
 	device_remove_attrs(dev);
-- 
2.25.1