KVM: Destroy target device if coalesced MMIO unregistration fails

commit b1cb1fac upstream.

Destroy and free the target coalesced MMIO device if unregistering said
device fails.  As clearly noted in the code, kvm_io_bus_unregister_dev()
does not destroy the target device.

  BUG: memory leak
  unreferenced object 0xffff888112a54880 (size 64):
    comm "syz-executor.2", pid 5258, jiffies 4297861402 (age 14.129s)
    hex dump (first 32 bytes):
      38 c7 67 15 00 c9 ff ff 38 c7 67 15 00 c9 ff ff  8.g.....8.g.....
      e0 c7 e1 83 ff ff ff ff 00 30 67 15 00 c9 ff ff  .........0g.....
    backtrace:
      [<0000000006995a8a>] kmalloc include/linux/slab.h:556 [inline]
      [<0000000006995a8a>] kzalloc include/linux/slab.h:690 [inline]
      [<0000000006995a8a>] kvm_vm_ioctl_register_coalesced_mmio+0x8e/0x3d0 arch/x86/kvm/../../../virt/kvm/coalesced_mmio.c:150
      [<00000000022550c2>] kvm_vm_ioctl+0x47d/0x1600 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3323
      [<000000008a75102f>] vfs_ioctl fs/ioctl.c:46 [inline]
      [<000000008a75102f>] file_ioctl fs/ioctl.c:509 [inline]
      [<000000008a75102f>] do_vfs_ioctl+0xbab/0x1160 fs/ioctl.c:696
      [<0000000080e3f669>] ksys_ioctl+0x76/0xa0 fs/ioctl.c:713
      [<0000000059ef4888>] __do_sys_ioctl fs/ioctl.c:720 [inline]
      [<0000000059ef4888>] __se_sys_ioctl fs/ioctl.c:718 [inline]
      [<0000000059ef4888>] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:718
      [<000000006444fa05>] do_syscall_64+0x9f/0x4e0 arch/x86/entry/common.c:290
      [<000000009a4ed50b>] entry_SYSCALL_64_after_hwframe+0x49/0xbe

  BUG: leak checking failed

Fixes: 5d3c4c79 ("KVM: Stop looking for coalesced MMIO zones if the bus is destroyed")
Cc: stable@vger.kernel.org
Reported-by: 柳菁峰 <liujingfeng@qianxin.com>
Reported-by: Michal Luczaj <mhal@rbox.co>
Link: https://lore.kernel.org/r/20221219171924.67989-1-seanjc@google.com
Link: https://lore.kernel.org/all/20230118220003.1239032-1-mhal@rbox.co


Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>