platform/mellanox: fix potential race in mlxbf-tmfifo driver

This commit adds memory barrier for the 'vq' update in function
mlxbf_tmfifo_virtio_find_vqs() to avoid potential race due to
out-of-order memory write. It also adds barrier for the 'is_ready'
flag to make sure the initializations are visible before this flag
is checked.

Signed-off-by: Liming Sun <limings@nvidia.com>
Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
Link: https://lore.kernel.org/r/b98c0ab61d644ba38fa9b3fd1607b138b0dd820b.1682518748.git.limings@nvidia.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c
index 91a077c35b8b86426d380446bb9d80a77152463e..a79318e90a13917ab090c363de3cb6c038a57bb0 100644 (file)
--- a/drivers/platform/mellanox/mlxbf-tmfifo.c
+++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
@@ -784,7 +784,7 @@ static void mlxbf_tmfifo_rxtx(struct mlxbf_tmfifo_vring *vring, bool is_rx)
        fifo = vring->fifo;
 
        /* Return if vdev is not ready. */
-       if (!fifo->vdev[devid])
+       if (!fifo || !fifo->vdev[devid])
                return;
 
        /* Return if another vring is running. */
@@ -980,9 +980,13 @@ static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
 
                vq->num_max = vring->num;
 
+               vq->priv = vring;
+
+               /* Make vq update visible before using it. */
+               virtio_mb(false);
+
                vqs[i] = vq;
                vring->vq = vq;
-               vq->priv = vring;
        }
 
        return 0;
@@ -1302,6 +1306,9 @@ static int mlxbf_tmfifo_probe(struct platform_device *pdev)
 
        mod_timer(&fifo->timer, jiffies + MLXBF_TMFIFO_TIMER_INTERVAL);
 
+       /* Make all updates visible before setting the 'is_ready' flag. */
+       virtio_mb(false);
+
        fifo->is_ready = true;
        return 0;