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SubjectRe: net/mlx5: Refactor tc flow attributes structure
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On Mon, 2020-09-28 at 17:06 +0100, Colin Ian King wrote:
> Hi,
>
> static analysis with Coverity has found a null pointer dereference
> issue
> with the following commit:
>
> commit c620b772152b8274031083bdb2e11c963e596c5c
> Author: Ariel Levkovich <lariel@mellanox.com>
> Date: Thu Apr 30 05:54:08 2020 +0300
>
> net/mlx5: Refactor tc flow attributes structure
>
> The analysis is as follows:
>
> 1240 slow_attr =
> mlx5_alloc_flow_attr(MLX5_FLOW_NAMESPACE_FDB);
>
> 1. Condition !slow_attr, taking true branch.
> 2. var_compare_op: Comparing slow_attr to null implies that
> slow_attr might be null.
>
> 1241 if (!slow_attr)
> 1242 mlx5_core_warn(flow->priv->mdev, "Unable to
> unoffload slow path rule\n");
> 1243
> 1244 memcpy(slow_attr, flow->attr, ESW_FLOW_ATTR_SZ);
>
> Dereference after null check (FORWARD_NULL)
> 3. var_deref_op: Dereferencing null pointer slow_attr.
>
> 1245 slow_attr->action = MLX5_FLOW_CONTEXT_ACTION_FWD_DEST;
> 1246 slow_attr->esw_attr->split_count = 0;
> 1247 slow_attr->flags |= MLX5_ESW_ATTR_FLAG_SLOW_PATH;
> 1248 mlx5e_tc_unoffload_fdb_rules(esw, flow, slow_attr);
> 1249 flow_flag_clear(flow, SLOW);
> 1250 kfree(slow_attr);
>
> there is a !slow_attr check but if it slow_attr is null the code then
> dereferences it multiple times afterwards.
>
> Colin

Thanks Colin for the Report,

Ariel is handling this internally and we will be posting the patch
soon.



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