linux-kernel - Re: [PATCH net-next] net/mlx5e: Do not use err uninitialized in mlx5e_rep_add_meta_tunnel

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Date:   Thu, 25 Aug 2022 11:19:47 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Tom Rix <trix@...hat.com>,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        patches@...ts.linux.dev
Subject: Re: [PATCH net-next] net/mlx5e: Do not use err uninitialized in mlx5e_rep_add_meta_tunnel_rule()

On Thu, Aug 25, 2022 at 11:06 AM Nathan Chancellor <nathan@...nel.org> wrote:
>
> Clang warns:
>
>   drivers/net/ethernet/mellanox/mlx5/core/en_rep.c:481:6: error: variable 'err' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>           if (IS_ERR(flow_rule)) {
>               ^~~~~~~~~~~~~~~~~
>   drivers/net/ethernet/mellanox/mlx5/core/en_rep.c:489:9: note: uninitialized use occurs here
>           return err;
>                 ^~~
>   drivers/net/ethernet/mellanox/mlx5/core/en_rep.c:481:2: note: remove the 'if' if its condition is always true
>           if (IS_ERR(flow_rule)) {
>           ^~~~~~~~~~~~~~~~~~~~~~~
>   drivers/net/ethernet/mellanox/mlx5/core/en_rep.c:474:9: note: initialize the variable 'err' to silence this warning
>           int err;
>                 ^
>                   = 0
>   1 error generated.
>
> There is little reason to have the 'goto + error variable' construct in
> this function. Get rid of it and just return the PTR_ERR value in the if
> statement and 0 at the end.
>
> Fixes: 430e2d5e2a98 ("net/mlx5: E-Switch, Move send to vport meta rule creation")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1695
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>

Thanks for the fix!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en_rep.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
> index c8617a62e542..a977804137a8 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
> @@ -471,22 +471,18 @@ mlx5e_rep_add_meta_tunnel_rule(struct mlx5e_priv *priv)
>         struct mlx5_eswitch_rep *rep = rpriv->rep;
>         struct mlx5_flow_handle *flow_rule;
>         struct mlx5_flow_group *g;
> -       int err;
>
>         g = esw->fdb_table.offloads.send_to_vport_meta_grp;
>         if (!g)
>                 return 0;
>
>         flow_rule = mlx5_eswitch_add_send_to_vport_meta_rule(esw, rep->vport);
> -       if (IS_ERR(flow_rule)) {
> -               err = PTR_ERR(flow_rule);
> -               goto out;
> -       }
> +       if (IS_ERR(flow_rule))
> +               return PTR_ERR(flow_rule);
>
>         rpriv->send_to_vport_meta_rule = flow_rule;
>
> -out:
> -       return err;
> +       return 0;
>  }
>
>  static void
>
> base-commit: c19d893fbf3f2f8fa864ae39652c7fee939edde2
> --
> 2.37.2
>


-- 
Thanks,
~Nick Desaulniers