spi: use generic driver_override infrastructure

Overview

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

spi: use generic driver_override infrastructure

When a driver is probed through __driver_attach(), the bus' match() callback is called without the device lock held, thus accessing the driver_override field without a lock, which can cause a UAF.

Fix this by using the driver-core driver_override infrastructure taking care of proper locking internally.

Note that calling match() from __driver_attach() without the device lock held is intentional. [1]

Also note that we do not enable the driver_override feature of struct bus_type, as SPI - in contrast to most other buses - passes "" to sysfs_emit() when the driver_override pointer is NULL. Thus, printing "\n" instead of "(null)\n".

Affected

• Linux >= 5039563e7c25eccd7fec1de6706011009d1c5665 < 6e8eb467bed6aa1a563dba8f366c9fd76ba0004e
• Linux >= 5039563e7c25eccd7fec1de6706011009d1c5665 < eedf220442d13b6d97294e5b0ac8a2c38ee1a1a0
• Linux >= 5039563e7c25eccd7fec1de6706011009d1c5665 < c73a58661a760373d08a6883af4f0bb5cc991a67
• Linux >= 5039563e7c25eccd7fec1de6706011009d1c5665 < e0ae367a2de06c49aa1de6ec9b1ab6860bbb2cf0
• Linux >= 5039563e7c25eccd7fec1de6706011009d1c5665 < cc34d77dd48708d810c12bfd6f5bf03304f6c824
• Linux 4.20

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.