UBUNTU-CVE-2026-93228: Medium severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: svcrdma: Reject Write/Reply chunks with segcount 0 A peer can send a Write or Reply chunk whose segcount field is zero. xdrcheckwritechunk() only rejects segcount > rcmaxpages, so zero passes the range check, and xdrinlinedecode(stream, 0) returns the current (non-NULL) cursor without advancing. The function returns true and pclallocwrite() then links a struct svcrdmachunk with chsegcount == 0 onto rcwritepcl or rcreplypcl. An earlier patch in this series made pclforeachsegment() safe for chsegcount == 0, so this no longer drives the memory walk it used to. Rejecting the malformed frame at the decode boundary is still worthwhile as defense in depth: it keeps degenerate zero-segment chunks off the parsed chunk lists entirely, so any future consumer that walks chsegments directly cannot observe one, and it makes the zero-floor easy to backport to trees where the macro change is more intrusive. RFC 8166 has no meaning for a Write/Reply chunk that describes no remote buffer, so no legitimate client is affected. xdrcheckreplychunk() funnels Reply chunks through xdrcheckwritechunk() and inherits the same rejection. pclallocwrite() also links each chunk onto the parsed chunk list before filling its segment array. If a future change weakens the segcount-0 rejection, an incomplete chunk is visible to consumers during the fill loop. Reorder so that listaddtail() follows the segment fill loop, ensuring only fully-populated chunks appear on the list.