linux-kernel - Re: [PATCH net-next] mlx5: Restore err assignment in mlx5_mdev

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Date:   Sun, 31 May 2020 12:58:10 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, Parav Pandit <parav@...lanox.com>,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH net-next] mlx5: Restore err assignment in mlx5_mdev_init

On Fri, May 29, 2020 at 10:54:48PM -0700, Nathan Chancellor wrote:
> Clang warns:
>
> drivers/net/ethernet/mellanox/mlx5/core/main.c:1278:6: warning: variable
> 'err' is used uninitialized whenever 'if' condition is true
> [-Wsometimes-uninitialized]
>         if (!priv->dbg_root) {
>             ^~~~~~~~~~~~~~~
> drivers/net/ethernet/mellanox/mlx5/core/main.c:1303:9: note:
> uninitialized use occurs here
>         return err;
>                ^~~
> drivers/net/ethernet/mellanox/mlx5/core/main.c:1278:2: note: remove the
> 'if' if its condition is always false
>         if (!priv->dbg_root) {
>         ^~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/mellanox/mlx5/core/main.c:1259:9: note: initialize
> the variable 'err' to silence this warning
>         int err;
>                ^
>                 = 0
> 1 warning generated.
>
> This path previously returned -ENOMEM, restore that error code so that
> it is not uninitialized.
>
> Fixes: 810cbb25549b ("net/mlx5: Add missing mutex destroy")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1042
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/main.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c b/drivers/net/ethernet/mellanox/mlx5/core/main.c
> index df46b1fce3a7..ac68445fde2d 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
> @@ -1277,6 +1277,7 @@ static int mlx5_mdev_init(struct mlx5_core_dev *dev, int profile_idx)
>  					    mlx5_debugfs_root);
>  	if (!priv->dbg_root) {
>  		dev_err(dev->device, "mlx5_core: error, Cannot create debugfs dir, aborting\n");
> +		err = -ENOMEM;
>  		goto err_dbg_root;
                ^^^^^^^^^^^^^^^^^^ this is wrong.
Failure to create debugfs should never fail the driver.

>  	}
>
>
> base-commit: c0cc73b79123e67b212bd537a7af88e52c9fbeac
> --
> 2.27.0.rc0
>