IB/srpt: Don't return freed pointer from srpt_alloc_ioctx_ring()

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/ulp/srpt/ib_srpt.c

@@ -687,6 +687,7 @@ static struct srpt_ioctx **srpt_alloc_ioctx_ring(struct srpt_device *sdev,
 	while (--i >= 0)
 		srpt_free_ioctx(sdev, ring[i], dma_size, dir);
 	kfree(ring);
+	ring = NULL;
 out:
 	return ring;
 }