kernel: dm thin: fix use-after-free crash in dm_sm_register_threshold_callback

In the Linux kernel, the following vulnerability has been resolved: dm thin: fix use-after-free crash in dmsmregisterthresholdcallback Fault inject on pool metadata device reports: BUG: KASAN: use-after-free in dmpoolregistermetadatathreshold+0x40/0x80 Read of size 8 at addr ffff8881b9d50068 by...