spi: Fix use-after-free with devm_spi_alloc_*

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

spi: Fix use-after-free with devm_spi_alloc_*

We can't rely on the contents of the devres list during

spi_unregister_controller(), as the list is already torn down at the

time we perform devres_find() for devm_spi_release_controller. This

causes devices registered with devm_spi_alloc_{master,slave}() to be

mistakenly identified as legacy, non-devm managed devices and have their

reference counters decremented below 0.

------------[ cut here ]------------

WARNING: CPU: 1 PID: 660 at lib/refcount.c:28 refcount_warn_saturate+0x108/0x174

[<b0396f04>] (refcount_warn_saturate) from [<b03c56a4>] (kobject_put+0x90/0x98)

[<b03c5614>] (kobject_put) from [<b0447b4c>] (put_device+0x20/0x24)

r4:b6700140

[<b0447b2c>] (put_device) from [<b07515e8>] (devm_spi_release_controller+0x3c/0x40)

[<b07515ac>] (devm_spi_release_controller) from [<b045343c>] (release_nodes+0x84/0xc4)

r5:b6700180 r4:b6700100

[<b04533b8>] (release_nodes) from [<b0454160>] (devres_release_all+0x5c/0x60)

r8:b1638c54 r7:b117ad94 r6:b1638c10 r5:b117ad94 r4:b163dc10

[<b0454104>] (devres_release_all) from [<b044e41c>] (__device_release_driver+0x144/0x1ec)

r5:b117ad94 r4:b163dc10

[<b044e2d8>] (__device_release_driver) from [<b044f70c>] (device_driver_detach+0x84/0xa0)

r9:00000000 r8:00000000 r7:b117ad94 r6:b163dc54 r5:b1638c10 r4:b163dc10

[<b044f688>] (device_driver_detach) from [<b044d274>] (unbind_store+0xe4/0xf8)

Instead, determine the devm allocation state as a flag on the

controller which is guaranteed to be stable during cleanup.