IB/mlx4: Check iboe netdev pointer before dereferencing it

Unlike other parts of the mlx4_ib code, the function build_mlx_header()
doesn't check if the iboe netdev of the given port is valid before
dereferencing it, which can cause a crash if the ethernet interface
has already been taken down.

Fix this by checking for a valid netdev pointer before using it to get
the port MAC address.

Signed-off-by: Kleber Sacilotto de Souza <klebers@linux.vnet.ibm.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
index a6d8ea060ea8..f585eddef4b7 100644
--- a/drivers/infiniband/hw/mlx4/qp.c
+++ b/drivers/infiniband/hw/mlx4/qp.c
@@ -1407,6 +1407,7 @@ static int build_mlx_header(struct mlx4_ib_sqp *sqp, struct ib_send_wr *wr,
         struct mlx4_wqe_mlx_seg *mlx = wqe;
         struct mlx4_wqe_inline_seg *inl = wqe + sizeof *mlx;
         struct mlx4_ib_ah *ah = to_mah(wr->wr.ud.ah);
+        struct net_device *ndev;
         union ib_gid sgid;
         u16 pkey;
         int send_size;
@@ -1483,7 +1484,10 @@ static int build_mlx_header(struct mlx4_ib_sqp *sqp, struct ib_send_wr *wr,
 
                 memcpy(sqp->ud_header.eth.dmac_h, ah->av.eth.mac, 6);
                 /* FIXME: cache smac value? */
-                smac = to_mdev(sqp->qp.ibqp.device)->iboe.netdevs[sqp->qp.port - 1]->dev_addr;
+                ndev = to_mdev(sqp->qp.ibqp.device)->iboe.netdevs[sqp->qp.port - 1];
+                if (!ndev)
+                        return -ENODEV;
+                smac = ndev->dev_addr;
                 memcpy(sqp->ud_header.eth.smac_h, smac, 6);
                 if (!memcmp(sqp->ud_header.eth.smac_h, sqp->ud_header.eth.dmac_h, 6))
                         mlx->flags |= cpu_to_be32(MLX4_WQE_CTRL_FORCE_LOOPBACK);