[SCSI] fix race in scsi_target_reap

This patch (as1357) fixes a race in SCSI target allocation and
release.  Putting a target in the STARGET_DEL state isn't protected by
the host lock, so an old target structure could be reused by a new
device even though it's about to be deleted.  The cure is to change
the state while still holding the host lock.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/scsi_scan.c

@@ -492,19 +492,20 @@ void scsi_target_reap(struct scsi_target *starget)
 	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
 	unsigned long flags;
 	enum scsi_target_state state;
-	int empty;
+	int empty = 0;
 
 	spin_lock_irqsave(shost->host_lock, flags);
 	state = starget->state;
-	empty = --starget->reap_ref == 0 &&
-		list_empty(&starget->devices) ? 1 : 0;
+	if (--starget->reap_ref == 0 && list_empty(&starget->devices)) {
+		empty = 1;
+		starget->state = STARGET_DEL;
+	}
 	spin_unlock_irqrestore(shost->host_lock, flags);
 
 	if (!empty)
 		return;
 
 	BUG_ON(state == STARGET_DEL);
-	starget->state = STARGET_DEL;
 	if (state == STARGET_CREATED)
 		scsi_target_destroy(starget);
 	else