CVE-2021-47421

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

drm/amdgpu: handle the case of pci_channel_io_frozen only in amdgpu_pci_resume

In current code, when a PCI error state pci_channel_io_normal is detectd,

it will report PCI_ERS_RESULT_CAN_RECOVER status to PCI driver, and PCI

driver will continue the execution of PCI resume callback report_resume by

pci_walk_bridge, and the callback will go into amdgpu_pci_resume

finally, where write lock is releasd unconditionally without acquiring

such lock first. In this case, a deadlock will happen when other threads

start to acquire the read lock.

To fix this, add a member in amdgpu_device strucutre to cache

pci_channel_state, and only continue the execution in amdgpu_pci_resume

when it's pci_channel_io_frozen.