Re: [PATCH mlx5-next] net/mlx5: Check device memory pointer before usage

[Michal Swiatkowski <michal.swiatkowski@linux.intel.com>]

On Mon, Jun 30, 2025 at 01:35:53PM +0300, Leon Romanovsky wrote:
> From: Stav Aviram <saviram@nvidia.com>
> 
> Add a NULL check before accessing device memory to prevent a crash if
> dev->dm allocation in mlx5_init_once() fails.
> 
> Fixes: c9b9dcb430b3 ("net/mlx5: Move device memory management to mlx5_core")
> Signed-off-by: Stav Aviram <saviram@nvidia.com>
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> ---
>  drivers/infiniband/hw/mlx5/dm.c                  | 2 +-
>  drivers/net/ethernet/mellanox/mlx5/core/lib/dm.c | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/mlx5/dm.c b/drivers/infiniband/hw/mlx5/dm.c
> index b4c97fb62abf..9ded2b7c1e31 100644
> --- a/drivers/infiniband/hw/mlx5/dm.c
> +++ b/drivers/infiniband/hw/mlx5/dm.c
> @@ -282,7 +282,7 @@ static struct ib_dm *handle_alloc_dm_memic(struct ib_ucontext *ctx,
>  	int err;
>  	u64 address;
>  
> -	if (!MLX5_CAP_DEV_MEM(dm_db->dev, memic))
> +	if (!dm_db || !MLX5_CAP_DEV_MEM(dm_db->dev, memic))
>  		return ERR_PTR(-EOPNOTSUPP);
>  
>  	dm = kzalloc(sizeof(*dm), GFP_KERNEL);
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/dm.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/dm.c
> index 7c5516b0a844..8115071c34a4 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/lib/dm.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/dm.c
> @@ -30,7 +30,7 @@ struct mlx5_dm *mlx5_dm_create(struct mlx5_core_dev *dev)
>  
>  	dm = kzalloc(sizeof(*dm), GFP_KERNEL);
>  	if (!dm)
> -		return ERR_PTR(-ENOMEM);
> +		return NULL;
>  
>  	spin_lock_init(&dm->lock);
>  
> @@ -96,7 +96,7 @@ struct mlx5_dm *mlx5_dm_create(struct mlx5_core_dev *dev)
>  err_steering:
>  	kfree(dm);
>  
> -	return ERR_PTR(-ENOMEM);
> +	return NULL;

In mlx5_init_once() IS_ERR is used (still). It should be consistent.
Looks like you can use IS_ERR() instead of checking just dm_db, however,
mlx5_dm_create() returns also NULL. I am not sure if it is fine (will
not cause an error in mlx5_init_once()).

Maybe the best is to change a check in mlx5_init_once() from IS_ERROR()
to just !dm.

Thanks

>  }
>  
>  void mlx5_dm_cleanup(struct mlx5_core_dev *dev)
> -- 
> 2.50.0