net: phy: fix null-ptr-deref while probe() failed

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

net: phy: fix null-ptr-deref while probe() failed

I got a null-ptr-deref report as following when doing fault injection test:

BUG: kernel NULL pointer dereference, address: 0000000000000058

Oops: 0000 [#1] PREEMPT SMP KASAN PTI

CPU: 1 PID: 253 Comm: 507-spi-dm9051 Tainted: G B N 6.1.0-rc3+

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014

RIP: 0010:klist_put+0x2d/0xd0

Call Trace:

<TASK>

klist_remove+0xf1/0x1c0

device_release_driver_internal+0x23e/0x2d0

bus_remove_device+0x1bd/0x240

device_del+0x357/0x770

phy_device_remove+0x11/0x30

mdiobus_unregister+0xa5/0x140

release_nodes+0x6a/0xa0

devres_release_all+0xf8/0x150

device_unbind_cleanup+0x19/0xd0

//probe path:

phy_device_register()

device_add()

phy_connect

phy_attach_direct() //set device driver

probe() //it's failed, driver is not bound

device_bind_driver() // probe failed, it's not called

//remove path:

phy_device_remove()

device_del()

device_release_driver_internal()

__device_release_driver() //dev->drv is not NULL

klist_remove() <- knode_driver is not added yet, cause null-ptr-deref

In phy_attach_direct(), after setting the 'dev->driver', probe() fails,

device_bind_driver() is not called, so the knode_driver->n_klist is not

set, then it causes null-ptr-deref in __device_release_driver() while

deleting device. Fix this by setting dev->driver to NULL in the error

path in phy_attach_direct().