RDMA/ocrdma: Fix use after free in ocrdma_dealloc_ucontext_pd()

In ocrdma_dealloc_ucontext_pd() uctx->cntxt_pd is assigned to the variable
pd and then after uctx->cntxt_pd is freed, the variable pd is passed to
function _ocrdma_dealloc_pd() which dereferences pd directly or through
its call to ocrdma_mbx_dealloc_pd().

Reorder the free using the variable pd.

Cc: stable@vger.kernel.org
Fixes: 21a428a ("RDMA: Handle PD allocations by IB/core")
Link: https://lore.kernel.org/r/20201230024653.1516495-1-trix@redhat.com
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Author: Tom Rix

drivers/infiniband/hw/ocrdma/ocrdma_verbs.c

@@ -434,9 +434,9 @@ static void ocrdma_dealloc_ucontext_pd(struct ocrdma_ucontext *uctx)
 		pr_err("%s(%d) Freeing in use pdid=0x%x.\n",
 		       __func__, dev->id, pd->id);
 	}
-	kfree(uctx->cntxt_pd);
 	uctx->cntxt_pd = NULL;
 	_ocrdma_dealloc_pd(dev, pd);
+	kfree(pd);
 }
 
 static struct ocrdma_pd *ocrdma_get_ucontext_pd(struct ocrdma_ucontext *uctx)