=== Fix validation: rebuild dm.ko with combined DF-1639+DF-1640+DF-1642 patches ===
$ cd /usr/src/sys/dev/disk/dm && make obj && make
... (full module build output; compiles cleanly) ...
cc -O2 -pipe -D_KERNEL ... -c dm_ioctl.c
cc -Wl,--build-id=sha1 ... -r -o dm.ko device-mapper.o dm_dev.o dm_ioctl.o dm_pdev.o dm_table.o dm_target.o dm_target_error.o dm_target_zero.o
=== DM_BUILD_RC=0 ===
-rw-r--r--  1 root  wheel  56344 Jul 18 16:05 /usr/obj/usr/src/sys/dev/disk/dm/dm.ko
sha256(dm.ko) = c35491ad7a4ccafc402e82744c9e2e44609fe6962c62dc7452a9beaf9935c747
=== verify fix compiled in ===
$ strings dm.ko | grep -E "missing cmd_data|missing message"
%s: dm_table_load_ioctl: missing cmd_data array
%s: dm_message_ioctl: missing message string
=== MODULE LOADED + TESTED ===
kldload /usr/obj/usr/src/sys/dev/disk/dm/dm.ko  -> OK
./dm_poc 1639 -> rc=-1 errno=22 (Invalid argument)   # FIXED, no panic
./dm_poc 1640 -> rc=-1 errno=22 (Invalid argument)   # FIXED, no panic
./dm_poc 1642 -> rc=-1 errno=22 (Invalid argument)   # FIXED, no panic