CVE-2026-98365: RDMA/rxe: Fix integer overflow in mr_check_range() leading to OOB access

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

RDMA/rxe: Fix integer overflow in mrcheckrange() leading to OOB access

mrcheckrange() validates that [iova, iova+length) falls within the registered MR range using wraparound-prone arithmetic:

if (iova < mr->ibmr.iova || iova + length > mr->ibmr.iova + mr->ibmr.length)

A remote peer can craft an RDMA-Write/Read RETH so that iova + length wraps to 0 (e.g. iova=0xfffffffffffffff8, length=8), bypassing the check. rxemriovatoindex() then computes a huge index (int idx, only guarded by WARNON) and rxemrcopyxarray() dereferences mr->pageinfo[huge], causing an out-of-bounds read/write and a kernel oops that is triggerable by an unauthenticated remote peer.

Rewrite the check in overflow-safe form; the first two clauses guarantee that the subsequent subtractions do not underflow:

if (iova < mr->ibmr.iova || length > mr->ibmr.length || iova - mr->ibmr.iova > mr->ibmr.length - length)

With the fix, mrcheckrange() returns -EINVAL for the crafted iova and the responder reports REMOTEACCESSERROR instead of triggering the OOB.