[1/2,net-next] net/mlx5e: TC: Fix IS_ERR() vs NULL checks

The mlx5_tc_ct_init() function doesn't return error pointers it returns
NULL.  Also we need to set the error codes on this path.

Fixes: aedd133d17bc ("net/mlx5e: Support CT offload for tc nic flows")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_tc.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

On Sep 28, 2020, at 13:42, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> 
> The mlx5_tc_ct_init() function doesn't return error pointers it returns
> NULL.  Also we need to set the error codes on this path.
> 
> Fixes: aedd133d17bc ("net/mlx5e: Support CT offload for tc nic flows")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> drivers/net/ethernet/mellanox/mlx5/core/en_tc.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> index 104b1c339de0..438fbcf478d1 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> @@ -5224,8 +5224,10 @@ int mlx5e_tc_nic_init(struct mlx5e_priv *priv)
> 
>    tc->ct = mlx5_tc_ct_init(priv, tc->chains, &priv->fs.tc.mod_hdr,
>                 MLX5_FLOW_NAMESPACE_KERNEL);
> -    if (IS_ERR(tc->ct))
> +    if (!tc->ct) {
> +        err = -ENOMEM;
>        goto err_ct;
> +    }

Hi Dan,
That was implement like that on purpose. If mlx5_tc_init_ct returns NULL it means the device doesn’t support CT offload which can happen with older devices or old FW on the devices.
However, in this case we want to continue with the rest of the Tc initialization because we can still support other TC offloads. No need to fail the entire TC init in this case. Only if mlx5_tc_init_ct return err_ptr that means the tc init failed not because of lack of support but due to a real error and only then we want to fail the rest of the tc init.

Your change will break compatibility for devices/FW versions that don’t have CT offload support.

Ariel

> 
>    tc->netdevice_nb.notifier_call = mlx5e_tc_netdev_event;
>    err = register_netdevice_notifier_dev_net(priv->netdev,
> @@ -5300,8 +5300,10 @@ int mlx5e_tc_esw_init(struct rhashtable *tc_ht)
>                           esw_chains(esw),
>                           &esw->offloads.mod_hdr,
>                           MLX5_FLOW_NAMESPACE_FDB);
> -    if (IS_ERR(uplink_priv->ct_priv))
> +    if (!uplink_priv->ct_priv) {
> +        err = -ENOMEM;
>        goto err_ct;
> +    }
> 
>    mapping = mapping_create(sizeof(struct tunnel_match_key),
>                 TUNNEL_INFO_BITS_MASK, true);
> -- 
> 2.28.0
>

On Mon, Sep 28, 2020 at 06:31:04PM +0000, Ariel Levkovich wrote:
> On Sep 28, 2020, at 13:42, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> > 
> > The mlx5_tc_ct_init() function doesn't return error pointers it returns
> > NULL.  Also we need to set the error codes on this path.
> > 
> > Fixes: aedd133d17bc ("net/mlx5e: Support CT offload for tc nic flows")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> > drivers/net/ethernet/mellanox/mlx5/core/en_tc.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> > index 104b1c339de0..438fbcf478d1 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> > @@ -5224,8 +5224,10 @@ int mlx5e_tc_nic_init(struct mlx5e_priv *priv)
> > 
> >    tc->ct = mlx5_tc_ct_init(priv, tc->chains, &priv->fs.tc.mod_hdr,
> >                 MLX5_FLOW_NAMESPACE_KERNEL);
> > -    if (IS_ERR(tc->ct))
> > +    if (!tc->ct) {
> > +        err = -ENOMEM;
> >        goto err_ct;
> > +    }
> 
> Hi Dan,
> That was implement like that on purpose. If mlx5_tc_init_ct returns
> NULL it means the device doesn’t support CT offload which can happen
> with older devices or old FW on the devices.
> However, in this case we want to continue with the rest of the Tc
> initialization because we can still support other TC offloads. No
> need to fail the entire TC init in this case. Only if mlx5_tc_init_ct
> return err_ptr that means the tc init failed not because of lack of
> support but due to a real error and only then we want to fail the rest
> of the tc init.
> 
> Your change will break compatibility for devices/FW versions that
> don’t have CT offload support.
> 

I should have looked at this more closely.  It seems the bug is in
mlx5_tc_ct_init().

drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c
  1897  struct mlx5_tc_ct_priv *
  1898  mlx5_tc_ct_init(struct mlx5e_priv *priv, struct mlx5_fs_chains *chains,
  1899                  struct mod_hdr_tbl *mod_hdr,
  1900                  enum mlx5_flow_namespace_type ns_type)
  1901  {
  1902          struct mlx5_tc_ct_priv *ct_priv;
  1903          struct mlx5_core_dev *dev;
  1904          const char *msg;
  1905          int err;
  1906  
  1907          dev = priv->mdev;
  1908          err = mlx5_tc_ct_init_check_support(priv, ns_type, &msg);
  1909          if (err) {
  1910                  mlx5_core_warn(dev,
  1911                                 "tc ct offload not supported, %s\n",
  1912                                 msg);
  1913                  goto err_support;

This should probably return NULL and it does.

  1914          }
  1915  
  1916          ct_priv = kzalloc(sizeof(*ct_priv), GFP_KERNEL);
  1917          if (!ct_priv)
  1918                  goto err_alloc;

This should probably return an ERR_PTR(-ENOMEM) but it instead returns
NULL.

  1919  
  1920          ct_priv->zone_mapping = mapping_create(sizeof(u16), 0, true);
  1921          if (IS_ERR(ct_priv->zone_mapping)) {
  1922                  err = PTR_ERR(ct_priv->zone_mapping);
  1923                  goto err_mapping_zone;
                        ^^^^^^^^^^^^^^^^^^^^^^
This sets "err" but it still returns NULL.

Then in the caller if the mlx5_tc_ct_init() call returns an error
pointer, it should set the error code.  (NULL is a special case of
success etc).

Can you fix this and give me a reported-by tag?  I think my new analysis
is correct...

regards,
dan carpenter