Re: [PATCH net-next] net/mlx5e: Ensure macsec_rule is always initiailized in macsec_fs_{r,t}x_add_rule()

[Tom Rix]

On 9/8/22 8:32 AM, Nathan Chancellor wrote:
> Clang warns:
>
>    drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:539:6: error: variable 'macsec_rule' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>            if (err)
>                ^~~
>    drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:598:9: note: uninitialized use occurs here
>            return macsec_rule;
>                  ^~~~~~~~~~~
>    drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:539:2: note: remove the 'if' if its condition is always false
>            if (err)
>            ^~~~~~~~
>    drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:523:38: note: initialize the variable 'macsec_rule' to silence this warning
>            union mlx5e_macsec_rule *macsec_rule;
>                                                ^
>                                                = NULL
>    drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:1131:6: error: variable 'macsec_rule' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>            if (err)
>                ^~~
>    drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:1215:9: note: uninitialized use occurs here
>            return macsec_rule;
>                  ^~~~~~~~~~~
>    drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:1131:2: note: remove the 'if' if its condition is always false
>            if (err)
>            ^~~~~~~~
>    drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:1118:38: note: initialize the variable 'macsec_rule' to silence this warning
>            union mlx5e_macsec_rule *macsec_rule;
>                                                ^
>                                                = NULL
>    2 errors generated.
>
> If macsec_fs_{r,t}x_ft_get() fail, macsec_rule will be uninitialized.
> Use the existing initialization to NULL in the existing error path to
> ensure macsec_rule is always initialized.
>
> Fixes: e467b283ffd5 ("net/mlx5e: Add MACsec TX steering rules")
> Fixes: 3b20949cb21b ("net/mlx5e: Add MACsec RX steering rules")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1706
> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Reviewed-by: Tom Rix <trix@xxxxxxxxxx>
> ---
>
> The other fix I considered was shuffling the two if statements so that
> the allocation of macsec_rule came before the call to
> macsec_fs_{r,t}x_ft_get() but I was not sure what the implications of
> that change were.
>
> Also, I thought netdev was doing testing with clang so that new warnings
> do not show up. Did something break or stop working since this is the
> second time in two weeks that new warnings have appeared in -next?
>
>   .../net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c    | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c
> index 608fbbaa5a58..4467e88d7e7f 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c
> @@ -537,7 +537,7 @@ macsec_fs_tx_add_rule(struct mlx5e_macsec_fs *macsec_fs,
>   
>   	err = macsec_fs_tx_ft_get(macsec_fs);
>   	if (err)
> -		goto out_spec;
> +		goto out_spec_no_rule;
>   
>   	macsec_rule = kzalloc(sizeof(*macsec_rule), GFP_KERNEL);
>   	if (!macsec_rule) {
> @@ -591,6 +591,7 @@ macsec_fs_tx_add_rule(struct mlx5e_macsec_fs *macsec_fs,
>   
>   err:
>   	macsec_fs_tx_del_rule(macsec_fs, tx_rule);
> +out_spec_no_rule:
>   	macsec_rule = NULL;
>   out_spec:
>   	kvfree(spec);
> @@ -1129,7 +1130,7 @@ macsec_fs_rx_add_rule(struct mlx5e_macsec_fs *macsec_fs,
>   
>   	err = macsec_fs_rx_ft_get(macsec_fs);
>   	if (err)
> -		goto out_spec;
> +		goto out_spec_no_rule;
>   
>   	macsec_rule = kzalloc(sizeof(*macsec_rule), GFP_KERNEL);
>   	if (!macsec_rule) {
> @@ -1209,6 +1210,7 @@ macsec_fs_rx_add_rule(struct mlx5e_macsec_fs *macsec_fs,
>   
>   err:
>   	macsec_fs_rx_del_rule(macsec_fs, rx_rule);
> +out_spec_no_rule:
>   	macsec_rule = NULL;
>   out_spec:
>   	kvfree(spec);
>
> base-commit: 75554fe00f941c3c3d9344e88708093a14d2b4b8