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

In the Linux kernel, the following vulnerability has been resolved:

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

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().