Ubuntu: (CVE-2021-47549): linux vulnerability

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

sata_fsl: fix UAF in sata_fsl_port_stop when rmmod sata_fsl

When the `rmmod sata_fsl.ko` command is executed in the PPC64 GNU/Linux,
a bug is reported:
==================================================================
BUG: Unable to handle kernel data access on read at 0x80000800805b502c
Oops: Kernel access of bad area, sig: 11 [#1]
NIP [c0000000000388a4] .ioread32+0x4/0x20
LR [80000000000c6034] .sata_fsl_port_stop+0x44/0xe0 [sata_fsl]
Call Trace:
.free_irq+0x1c/0x4e0 (unreliable)
.ata_host_stop+0x74/0xd0 [libata]
.release_nodes+0x330/0x3f0
.device_release_driver_internal+0x178/0x2c0
.driver_detach+0x64/0xd0
.bus_remove_driver+0x70/0xf0
.driver_unregister+0x38/0x80
.platform_driver_unregister+0x14/0x30
.fsl_sata_driver_exit+0x18/0xa20 [sata_fsl]
.__se_sys_delete_module+0x1ec/0x2d0
.system_call_exception+0xfc/0x1f0
system_call_common+0xf8/0x200
==================================================================

The triggering of the BUG is shown in the following stack:

driver_detach
device_release_driver_internal
__device_release_driver
drv->remove(dev) --> platform_drv_remove/platform_remove
drv->remove(dev) --> sata_fsl_remove
iounmap(host_priv->hcr_base); <---- unmap
kfree(host_priv); <---- free
devres_release_all
release_nodes
dr->node.release(dev, dr->data) --> ata_host_stop
ap->ops->port_stop(ap) --> sata_fsl_port_stop
ioread32(hcr_base + HCONTROL) <---- UAF
host->ops->host_stop(host)

The iounmap(host_priv->hcr_base) and kfree(host_priv) functions should
not be executed in drv->remove. These functions should be executed in
host_stop after port_stop. Therefore, we move these functions to the
new function sata_fsl_host_stop and bind the new function to host_stop.