Re: [PATCH] net/mlx5e/core/en_fs: fix pointer dereference after free in mlx5e_execute_l2_action

From: Saeed Mahameed
Date: Sun Nov 05 2017 - 00:43:46 EST


On Sat, Nov 4, 2017 at 8:54 PM, Gustavo A. R. Silva
<garsilva@xxxxxxxxxxxxxx> wrote:
> hn is being kfree'd in mlx5e_del_l2_from_hash and then dereferenced
> by accessing hn->ai.addr
>
> Fix this by copying the MAC address into a local variable for its safe use
> in all possible execution paths within function mlx5e_execute_l2_action.
>
> Addresses-Coverity-ID: 1417789
> Fixes: eeb66cdb6826 ("net/mlx5: Separate between E-Switch and MPFS")
> Signed-off-by: Gustavo A. R. Silva <garsilva@xxxxxxxxxxxxxx>

Acked-by: Saeed Mahameed <saeedm@xxxxxxxxxxxx>

Looks good.
Thank you Gustavo.

> ---
> drivers/net/ethernet/mellanox/mlx5/core/en_fs.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_fs.c b/drivers/net/ethernet/mellanox/mlx5/core/en_fs.c
> index 850cdc9..4837045 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_fs.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_fs.c
> @@ -365,21 +365,24 @@ static void mlx5e_execute_l2_action(struct mlx5e_priv *priv,
> struct mlx5e_l2_hash_node *hn)
> {
> u8 action = hn->action;
> + u8 mac_addr[ETH_ALEN];
> int l2_err = 0;
>
> + ether_addr_copy(mac_addr, hn->ai.addr);
> +
> switch (action) {
> case MLX5E_ACTION_ADD:
> mlx5e_add_l2_flow_rule(priv, &hn->ai, MLX5E_FULLMATCH);
> - if (!is_multicast_ether_addr(hn->ai.addr)) {
> - l2_err = mlx5_mpfs_add_mac(priv->mdev, hn->ai.addr);
> + if (!is_multicast_ether_addr(mac_addr)) {
> + l2_err = mlx5_mpfs_add_mac(priv->mdev, mac_addr);
> hn->mpfs = !l2_err;
> }
> hn->action = MLX5E_ACTION_NONE;
> break;
>
> case MLX5E_ACTION_DEL:
> - if (!is_multicast_ether_addr(hn->ai.addr) && hn->mpfs)
> - l2_err = mlx5_mpfs_del_mac(priv->mdev, hn->ai.addr);
> + if (!is_multicast_ether_addr(mac_addr) && hn->mpfs)
> + l2_err = mlx5_mpfs_del_mac(priv->mdev, mac_addr);
> mlx5e_del_l2_flow_rule(priv, &hn->ai);
> mlx5e_del_l2_from_hash(hn);
> break;
> @@ -387,7 +390,7 @@ static void mlx5e_execute_l2_action(struct mlx5e_priv *priv,
>
> if (l2_err)
> netdev_warn(priv->netdev, "MPFS, failed to %s mac %pM, err(%d)\n",
> - action == MLX5E_ACTION_ADD ? "add" : "del", hn->ai.addr, l2_err);
> + action == MLX5E_ACTION_ADD ? "add" : "del", mac_addr, l2_err);
> }
>
> static void mlx5e_sync_netdev_addr(struct mlx5e_priv *priv)
> --
> 2.7.4
>
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