patch + kernel build + install + reboot transcript (guest /usr/src, 2026-10-13):

  $ cd /usr/src && patch -N -p1 < /tmp/fix5816.diff
  Patching file sys/kern/uipc_usrreq.c using Plan A...
  Hunk #1 succeeded at 48.
  Hunk #2 succeeded at 1434.
  Hunk #3 succeeded at 1455.
  Hunk #4 succeeded at 1503.
  done
  PATCHED

  $ make -j6 nativekernel KERNCONF=X86_64_GENERIC
  KBUILD_OK

  $ make installkernel KERNCONF=X86_64_GENERIC
  KINST_OK
  (shutdown -r now)

  post-reboot:
  DragonFly dfbsd 6.5-DEVELOPMENT #1: Tue Oct 13 04:30:17 UTC 2026
      root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64

patched-kernel results (uid=1001, fix_validation.log):
  global: 0 non-NULL exported pointers, 0 outside kernel range, so_pcb==xu_unpp held for all 4 records
patched-kernel results (uid=0, functionality retained):
  global: 24 non-NULL exported pointers, 0 outside kernel range, so_pcb==xu_unpp held for all 4 records