[PATCH v2 1/2] scsi: leapraid: balance host references for firmware log VMAs

leapraid_fw_mmap() keeps the Scsi_Host reference obtained while
looking up the adapter for the lifetime of the initial VMA.  The VMA
close callback drops that reference.

The open callback is also invoked when a VMA is duplicated or split,
but it only increments mmap_refcnt.  Since every corresponding close
callback drops a host reference, cloning the mapping can release the
host while another VMA still refers to the adapter.

Take a host device reference for every VMA open and release the lookup
reference once the initial mapping has acquired its own reference.  Use
get_device() because a VMA can be cloned after the host enters SHOST_DEL;
an existing VMA still pins the host at that point and open cannot fail.

Fixes: 5597088c9e79 ("scsi: leapraid: Add new SCSI driver")
Signed-off-by: Linmao Li <[email protected]>
---
 drivers/scsi/leapraid/leapraid_app.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/leapraid/leapraid_app.c b/drivers/scsi/leapraid/leapraid_app.c
index 742f19c07fcbb..841027ce2501c 100644
--- a/drivers/scsi/leapraid/leapraid_app.c
+++ b/drivers/scsi/leapraid/leapraid_app.c
@@ -697,6 +697,7 @@ static void leapraid_fw_mmap_open(struct vm_area_struct *vma)
 	if (!adapter)
 		return;
 
+	get_device(&adapter->shost->shost_gendev);
 	atomic_inc(&adapter->fw_log_desc.mmap_refcnt);
 }
 
@@ -767,7 +768,6 @@ static int leapraid_fw_mmap(struct file *filp, struct vm_area_struct *vma)
 	vma->vm_private_data = adapter;
 	vma->vm_ops = &leapraid_fw_mmap_vm_ops;
 	leapraid_fw_mmap_open(vma);
-	adapter = NULL;
 
 	rc = 0;
 out_put:
-- 
2.25.1