net/mlx5: Check device memory pointer before usage

Add a NULL check before accessing device memory to prevent a crash if
dev->dm allocation in mlx5_init_once() fails.

Fixes: c9b9dcb ("net/mlx5: Move device memory management to mlx5_core")
Signed-off-by: Stav Aviram <saviram@nvidia.com>
Link: https://patch.msgid.link/c88711327f4d74d5cebc730dc629607e989ca187.1751370035.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>

Author: saviramnvidia

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);

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;
 }
 
 void mlx5_dm_cleanup(struct mlx5_core_dev *dev)

drivers/net/ethernet/mellanox/mlx5/core/main.c

@@ -1102,9 +1102,6 @@ static int mlx5_init_once(struct mlx5_core_dev *dev)
 	}
 
 	dev->dm = mlx5_dm_create(dev);
-	if (IS_ERR(dev->dm))
-		mlx5_core_warn(dev, "Failed to init device memory %ld\n", PTR_ERR(dev->dm));
-
 	dev->tracer = mlx5_fw_tracer_create(dev);
 	dev->hv_vhca = mlx5_hv_vhca_create(dev);
 	dev->rsc_dump = mlx5_rsc_dump_create(dev);