CVE-2026-98949: drm/imagination: Fix reference and vm_bo handling in remap()

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

drm/imagination: Fix reference and vmbo handling in remap()

When a map overlaps part of an existing mapping, pvrvmgpuvaremap() splits the mapping into prev/next parts covering what the request did not take, instead of creating something new. It gets two things wrong.

- A GEM reference is taken for each part but it's never needed and never dropped, so it leaks one reference per split (remap-next-in-2m in tests/imagination/pvrvmmap.c):

CRITICAL: 33558528 bytes of shmem still held after close

- The parts still belong to the original object being split, but pvrvmgpuvaremap() links them to ctx->gpuvmbo, the new object's vmbo:

prevva --obj--> BOA BOB <--obj-- vmbo (ctx->gpuvmbo) \link/ (mismatch: BOA != BOB)

drmgpuvalink() catches the mismatch:

WARNING: drivers/gpu/drm/drmgpuvm.c:2108 at drmgpuvalink+0x2ec/0x310 drmWARNON(obj != vmbo->obj) Call trace: drmgpuvalink pvrvmgpuvaremap drmgpuvmsmmap pvrvmmap pvrioctlvmmap

Link them to op->remap.unmap->va->vmbo instead.

The locking of the GPUVA lists of the other objects touched by a split is not addressed here; it is handled by switching the GPUVM to immediate mode.