Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates
 216.228.112.34 as permitted sender) receiver=protection.outlook.com;
 client-ip=216.228.112.34; helo=mail.nvidia.com;
Date:   Sun, 30 May 2021 11:17:21 +0300
From:   Eli Cohen <elic@nvidia.com>
To:     "Michael S. Tsirkin" <mst@redhat.com>
CC:     <jasowang@redhat.com>, <virtualization@lists.linux-foundation.org>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] vdpa/mlx5: Fix possible failure in umem size
 calculation
Message-ID: <20210530081721.GB119906@mtl-vdi-166.wap.labs.mlnx>
References: <20210530063214.183335-1-elic@nvidia.com>
 <20210530040523-mutt-send-email-mst@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20210530040523-mutt-send-email-mst@kernel.org>
User-Agent: Mutt/1.9.5 (bf161cf53efb) (2018-04-13)
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 May 2021 08:17:26.6380
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: bcebba7a-1e75-48c2-8ce5-08d923435c50
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com]
X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT023.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN8PR12MB3057
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Sun, May 30, 2021 at 04:05:57AM -0400, Michael S. Tsirkin wrote:
> On Sun, May 30, 2021 at 09:32:14AM +0300, Eli Cohen wrote:
> > umem size is a 32 bit unsigned value so assigning it to an int could
> > cause false failures. Set the calculated value inside the function and
> > modify function name to reflect the fact it updates the size.
> > 
> > Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
> > Signed-off-by: Eli Cohen <elic@nvidia.com>
> 
> could you clarify the impact of the bug please?
> 

This was found by code revew. I did not see it causing trouble becuase
umem sizes are small enough to fit in int. Nevertheless it's a bug that
deserves a fix.

> 
> > ---
> >  drivers/vdpa/mlx5/net/mlx5_vnet.c | 15 +++++----------
> >  1 file changed, 5 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > index 53312f0460ad..fdf3e74bffbd 100644
> > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > @@ -610,8 +610,8 @@ static void cq_destroy(struct mlx5_vdpa_net *ndev, u16 idx)
> >  	mlx5_db_free(ndev->mvdev.mdev, &vcq->db);
> >  }
> >  
> > -static int umem_size(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq, int num,
> > -		     struct mlx5_vdpa_umem **umemp)
> > +static void set_umem_size(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq, int num,
> > +			  struct mlx5_vdpa_umem **umemp)
> >  {
> >  	struct mlx5_core_dev *mdev = ndev->mvdev.mdev;
> >  	int p_a;
> > @@ -634,7 +634,7 @@ static int umem_size(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq
> >  		*umemp = &mvq->umem3;
> >  		break;
> >  	}
> > -	return p_a * mvq->num_ent + p_b;
> > +	(*umemp)->size = p_a * mvq->num_ent + p_b;
> >  }
> >  
> >  static void umem_frag_buf_free(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_umem *umem)
> > @@ -650,15 +650,10 @@ static int create_umem(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *m
> >  	void *in;
> >  	int err;
> >  	__be64 *pas;
> > -	int size;
> >  	struct mlx5_vdpa_umem *umem;
> >  
> > -	size = umem_size(ndev, mvq, num, &umem);
> > -	if (size < 0)
> > -		return size;
> > -
> > -	umem->size = size;
> > -	err = umem_frag_buf_alloc(ndev, umem, size);
> > +	set_umem_size(ndev, mvq, num, &umem);
> > +	err = umem_frag_buf_alloc(ndev, umem, umem->size);
> >  	if (err)
> >  		return err;
> >  
> > -- 
> > 2.31.1
>