Re: [PATCH] net/mlx5: fix potential null dereference when enable shared FDB

[Tariq Toukan]

On 03/04/2025 12:52, Charles Han(韩春超) wrote:
> -ENXIO indicates "No such device or address". I've found that in mlx5/core, if mlx5_get_flow_namespace() returns null, it basically returns -EOPNOTSUPP.

Please do not top-post.

+1.
If namespace is not found it's due to lack of support.


> -----邮件原件-----
> 发件人: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx>
> 发送时间: 2025年4月2日 19:02
> 收件人: Charles Han(韩春超) <hanchunchao@xxxxxxxxxx>
> 抄送: netdev@xxxxxxxxxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; saeedm@xxxxxxxxxx; leon@xxxxxxxxxx; tariqt@xxxxxxxxxx; andrew+netdev@xxxxxxx; davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; markzhang@xxxxxxxxxx; mbloch@xxxxxxxxxx
> 主题: Re: [PATCH] net/mlx5: fix potential null dereference when enable shared FDB
>
> On 4/2/25 11:43, Charles Han wrote:
> > mlx5_get_flow_namespace() may return a NULL pointer, dereferencing it
> > without NULL check may lead to NULL dereference.
> > Add a NULL check for ns.
> >
> > Fixes: db202995f503 ("net/mlx5: E-Switch, add logic to enable shared
> > FDB")
> > Signed-off-by: Charles Han <hanchunchao@xxxxxxxxxx>

Acked-by: Tariq Toukan <tariqt@xxxxxxxxxx>

> > ---
> >    .../net/ethernet/mellanox/mlx5/core/eswitch_offloads.c | 10 ++++++++++
> >    drivers/net/ethernet/mellanox/mlx5/core/fs_cmd.c       |  5 +++++
> >    2 files changed, 15 insertions(+)
> >
> > diff --git
> > a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> > b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> > index a6a8eea5980c..dc58e4c2d786 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> > @@ -2667,6 +2667,11 @@ static int esw_set_slave_root_fdb(struct mlx5_core_dev *master,
> >    	if (master) {
> >    		ns = mlx5_get_flow_namespace(master,
> >    					     MLX5_FLOW_NAMESPACE_FDB);
> > +		if (!ns) {
> > +			mlx5_core_warn(master, "Failed to get flow namespace\n");
> > +			return -EOPNOTSUPP;
>
> I would return -ENXIO in such cases, you were searching and not found that.
>
> IOW it is obvious that dereferencing a null ptr is not supported.
>
> If you agree, please apply the same comment for your other patch:
> https://lore.kernel.org/netdev/20250402093221.3253-1-hanchunchao@xxxxxxxxxx/T/#u
>
> > +		}
> > +
> >    		root = find_root(&ns->node);
> >    		mutex_lock(&root->chain_lock);
> >    		MLX5_SET(set_flow_table_root_in, in, @@ -2679,6 +2684,11 @@ static
> > int esw_set_slave_root_fdb(struct mlx5_core_dev *master,
> >    	} else {
> >    		ns = mlx5_get_flow_namespace(slave,
> >    					     MLX5_FLOW_NAMESPACE_FDB);
> > +		if (!ns) {
> > +			mlx5_core_warn(slave, "Failed to get flow namespace\n");
> > +			return -EOPNOTSUPP;
> > +		}
> > +
> >    		root = find_root(&ns->node);
> >    		mutex_lock(&root->chain_lock);
> >    		MLX5_SET(set_flow_table_root_in, in, table_id, diff --git
> > a/drivers/net/ethernet/mellanox/mlx5/core/fs_cmd.c
> > b/drivers/net/ethernet/mellanox/mlx5/core/fs_cmd.c
> > index a47c29571f64..18e59f6a0f2d 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/fs_cmd.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/fs_cmd.c
> > @@ -186,6 +186,11 @@ static int mlx5_cmd_set_slave_root_fdb(struct mlx5_core_dev *master,
> >    	} else {
> >    		ns = mlx5_get_flow_namespace(slave,
> >    					     MLX5_FLOW_NAMESPACE_FDB);
> > +		if (!ns) {
> > +			mlx5_core_warn(slave, "Failed to get flow namespace\n");
> > +			return -EOPNOTSUPP;
> > +		}
> > +
> >    		root = find_root(&ns->node);
> >    		MLX5_SET(set_flow_table_root_in, in, table_id,
> >    			 root->root_ft->id);