CVE-2026-98894: drm/amd/ras: reset CPER ring on corrupt entry size

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

drm/amd/ras: reset CPER ring on corrupt entry size

When CPER ring overflow handling advances the read pointer, it trusts the parsed entry size from the current ring contents. Corrupt CPER data can produce an entry size that does not advance rptr after dword conversion and pointer masking.

In that case the recovery loop keeps testing the same location while holding the CPER ring mutex. This can hang the worker that is writing the next CPER record.

Detect a no-progress rptr update and reset the CPER ring to an empty state instead. This drops the corrupt contents and lets the writer leave the recovery path without spinning.