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

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Message-ID: <20250701113318.GB6278@unreal>
Date: Tue, 1 Jul 2025 14:33:18 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
Cc: Jason Gunthorpe <jgg@...dia.com>, Stav Aviram <saviram@...dia.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, linux-rdma@...r.kernel.org,
	Mark Bloch <markb@...lanox.com>, netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>, Saeed Mahameed <saeedm@...dia.com>,
	Tariq Toukan <tariqt@...dia.com>
Subject: Re: [PATCH mlx5-next] net/mlx5: Check device memory pointer before
 usage

On Mon, Jun 30, 2025 at 12:56:46PM +0200, Michal Swiatkowski wrote:
> On Mon, Jun 30, 2025 at 01:35:53PM +0300, Leon Romanovsky wrote:
> > From: Stav Aviram <saviram@...dia.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@...dia.com>
> > Signed-off-by: Leon Romanovsky <leonro@...dia.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.

We need to remove IS_ERR() check from all places.

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