Re: [PATCH v2 net] net/mlx5: DR, prevent potential error pointer dereference

[Tariq Toukan <ttoukan.linux@gmail.com>]

On 03/12/2024 11:45, Dan Carpenter wrote:
> The dr_domain_add_vport_cap() function generally returns NULL on error
> but sometimes we want it to return ERR_PTR(-EBUSY) so the caller can
> retry.  The problem here is that "ret" can be either -EBUSY or -ENOMEM
> and if it's and -ENOMEM then the error pointer is propogated back and
> eventually dereferenced in dr_ste_v0_build_src_gvmi_qpn_tag().
> 
> Fixes: 11a45def2e19 ("net/mlx5: DR, Add support for SF vports")
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> Reviewed-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
> ---
> v2: Fix a typo in the commit message.  "generally".
> 
>   .../net/ethernet/mellanox/mlx5/core/steering/sws/dr_domain.c    | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/steering/sws/dr_domain.c b/drivers/net/ethernet/mellanox/mlx5/core/steering/sws/dr_domain.c
> index 3d74109f8230..a379e8358f82 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/steering/sws/dr_domain.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/steering/sws/dr_domain.c
> @@ -297,6 +297,8 @@ dr_domain_add_vport_cap(struct mlx5dr_domain *dmn, u16 vport)
>   	if (ret) {
>   		mlx5dr_dbg(dmn, "Couldn't insert new vport into xarray (%d)\n", ret);
>   		kvfree(vport_caps);
> +		if (ret != -EBUSY)
> +			return NULL;
>   		return ERR_PTR(ret);
>   	}
>   

Thanks for your patch.

It would be clearer to the reader if you test against -EBUSY and return 
ERR_PTR(-EBUSY).
Otherwise, return NULL.

Or at least modify ERR_PTR(ret) to be ERR_PTR(-EBUSY).

Keeping "return ERR_PTR(ret);" does not make it clear that we have only 
2 possible return values here.