drm/shmem_helper: Check VMA boundaries for PMD mappings

drm/shmem_helper: Check VMA boundaries for PMD mappings

In the ->huge_fault handler do not install a PMD huge page
mapping if the huge page exceeds the boundaries of the VMA.

All other ->huge_fault handlers have similar checks and the
resulting mapping will trigger a VM_BUG_ON_VMA() if it ever
reaches copy_pmd_range().

Cc: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: stable@vger.kernel.org
Fixes: fc3bbf34e643 ("drm/shmem-helper: Fix huge page mapping in fault handler")
Signed-off-by: Christian A. Ehrhardt <lk@c--e.de>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patch.msgid.link/20260622215718.1532689-1-lk@c--e.de
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>