Re: [PATCH net v5] net: systemport: Add error pointer checks in bcm_sysport_map_queues() and bcm_sysport_unmap_queues()

[Vladimir Oltean <vladimir.oltean@nxp.com>]

On Fri, Sep 27, 2024 at 12:02:36PM +0100, Simon Horman wrote:
> + Vladimir

Thanks for adding me, Simon.

> On Thu, Sep 26, 2024 at 04:05:12PM +0000, Dipendra Khadka wrote:
> > Add error pointer checks in bcm_sysport_map_queues() and
> > bcm_sysport_unmap_queues() after calling dsa_port_from_netdev().
> > 
> > Fixes: 1593cd40d785 ("net: systemport: use standard netdevice notifier to detect DSA presence")
> > Signed-off-by: Dipendra Khadka <kdipendra88@gmail.com>
> 
> Reviewed-by: Simon Horman <horms@kernel.org>
> 
> > ---
> > v5: 
> >  -Removed extra parentheses
> > v4: https://lore.kernel.org/all/20240925152927.4579-1-kdipendra88@gmail.com/
> >  - Removed wrong and used correct Fixes: tag
> > v3: https://lore.kernel.org/all/20240924185634.2358-1-kdipendra88@gmail.com/
> >  - Updated patch subject
> >  - Updated patch description
> >  - Added Fixes: tags
> >  - Fixed typo from PRT_ERR to PTR_ERR
> >  - Error is checked just after  assignment
> > v2: https://lore.kernel.org/all/20240923053900.1310-1-kdipendra88@gmail.com/
> >  - Change the subject of the patch to net
> > v1: https://lore.kernel.org/all/20240922181739.50056-1-kdipendra88@gmail.com/
> >  drivers/net/ethernet/broadcom/bcmsysport.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/broadcom/bcmsysport.c b/drivers/net/ethernet/broadcom/bcmsysport.c
> > index c9faa8540859..a7ad829f11d4 100644
> > --- a/drivers/net/ethernet/broadcom/bcmsysport.c
> > +++ b/drivers/net/ethernet/broadcom/bcmsysport.c
> > @@ -2331,11 +2331,15 @@ static const struct net_device_ops bcm_sysport_netdev_ops = {
> >  static int bcm_sysport_map_queues(struct net_device *dev,
> >  				  struct net_device *slave_dev)
> >  {
> > -	struct dsa_port *dp = dsa_port_from_netdev(slave_dev);
> >  	struct bcm_sysport_priv *priv = netdev_priv(dev);
> >  	struct bcm_sysport_tx_ring *ring;
> >  	unsigned int num_tx_queues;
> >  	unsigned int q, qp, port;
> > +	struct dsa_port *dp;
> > +
> > +	dp = dsa_port_from_netdev(slave_dev);
> > +	if (IS_ERR(dp))
> > +		return PTR_ERR(dp);
> >  
> >  	/* We can't be setting up queue inspection for non directly attached
> >  	 * switches
> > @@ -2386,11 +2390,15 @@ static int bcm_sysport_map_queues(struct net_device *dev,
> >  static int bcm_sysport_unmap_queues(struct net_device *dev,
> >  				    struct net_device *slave_dev)
> >  {
> > -	struct dsa_port *dp = dsa_port_from_netdev(slave_dev);
> >  	struct bcm_sysport_priv *priv = netdev_priv(dev);
> >  	struct bcm_sysport_tx_ring *ring;
> >  	unsigned int num_tx_queues;
> >  	unsigned int q, qp, port;
> > +	struct dsa_port *dp;
> > +
> > +	dp = dsa_port_from_netdev(slave_dev);
> > +	if (IS_ERR(dp))
> > +		return PTR_ERR(dp);

I don't see an explanation anywhere as for why dsa_port_from_netdev()
could ever return a pointer-encoded error here? hmm? Did you follow the
call path and found a problem?