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

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

[Dipendra Khadka]

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>
---
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);
 
 	port = dp->index;
 
-- 
2.43.0

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

[Simon Horman]

+ Vladimir

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);
>  
>  	port = dp->index;
>  
> -- 
> 2.43.0
> 

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

[Vladimir Oltean]

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?

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

[Vladimir Oltean]

On Fri, Sep 27, 2024 at 02:29:58PM +0300, Vladimir Oltean wrote:
> > > +	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?

To make my point even clearer. As the code goes:

bool dsa_user_dev_check(const struct net_device *dev)
{
	// This dereferences "dev" without a NULL pointer check.
	// If the kernel did not crash, it means that "dev" is not null.
	return dev->netdev_ops == &dsa_user_netdev_ops;
}

static int bcm_sysport_netdevice_event(struct notifier_block *nb,
				       unsigned long event, void *ptr)
{
	...
	switch (event) {
	case NETDEV_CHANGEUPPER:
		...
		if (!dsa_user_dev_check(info->upper_dev))
			return NOTIFY_DONE;

		// we know here that dsa_user_dev_check() is true, and
		// no one changes dev->netdev_ops at runtime, to suspect
		// it could become false after it just returned true.
		// Even if it did, we are under rtnl_lock(), and whoever
		// did that better also acquired rtnl_lock(). Thus,
		// there is enough guarantee that this also remains true
		// below.
		if (info->linking)
			ret = bcm_sysport_map_queues(dev, info->upper_dev);
		else
			ret = bcm_sysport_unmap_queues(dev, info->upper_dev);
	}
	...
}

struct dsa_port *dsa_port_from_netdev(struct net_device *netdev)
{
	if (!netdev || !dsa_user_dev_check(netdev))
		return ERR_PTR(-ENODEV);

	return dsa_user_to_port(netdev);
}

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);
	...
}

So, if both conditions for dsa_port_from_netdev() to return ERR_PTR(-ENODEV)
can only be false, why would we add an error check? Is it to appease a
static analysis tool which doesn't analyze things very far? Or is there
an actual problem?

And why does this have a Fixes: tag and the expectation to be included
as a bug fix to stable kernels?

And why is the author of the blamed patch even CCed only at v5?!

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

[Dipendra Khadka]

Hi Vladimir,

On Fri, 27 Sept 2024 at 17:45, Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
>
> On Fri, Sep 27, 2024 at 02:29:58PM +0300, Vladimir Oltean wrote:
> > > > + 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?
>

Yeah, you are right. I ran smatch to find this and saw there is no
validation. I did not see any problem as you said. I thought it would
be better to include this change. If you say there is no point for
this change, then that's also fine for me. I got the chance to learn
new things.

> To make my point even clearer. As the code goes:
>
> bool dsa_user_dev_check(const struct net_device *dev)
> {
>         // This dereferences "dev" without a NULL pointer check.
>         // If the kernel did not crash, it means that "dev" is not null.
>         return dev->netdev_ops == &dsa_user_netdev_ops;
> }
>
> static int bcm_sysport_netdevice_event(struct notifier_block *nb,
>                                        unsigned long event, void *ptr)
> {
>         ...
>         switch (event) {
>         case NETDEV_CHANGEUPPER:
>                 ...
>                 if (!dsa_user_dev_check(info->upper_dev))
>                         return NOTIFY_DONE;
>
>                 // we know here that dsa_user_dev_check() is true, and
>                 // no one changes dev->netdev_ops at runtime, to suspect
>                 // it could become false after it just returned true.
>                 // Even if it did, we are under rtnl_lock(), and whoever
>                 // did that better also acquired rtnl_lock(). Thus,
>                 // there is enough guarantee that this also remains true
>                 // below.
>                 if (info->linking)
>                         ret = bcm_sysport_map_queues(dev, info->upper_dev);
>                 else
>                         ret = bcm_sysport_unmap_queues(dev, info->upper_dev);
>         }
>         ...
> }
>
> struct dsa_port *dsa_port_from_netdev(struct net_device *netdev)
> {
>         if (!netdev || !dsa_user_dev_check(netdev))
>                 return ERR_PTR(-ENODEV);
>
>         return dsa_user_to_port(netdev);
> }
>
> 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);
>         ...
> }
>
> So, if both conditions for dsa_port_from_netdev() to return ERR_PTR(-ENODEV)
> can only be false, why would we add an error check? Is it to appease a
> static analysis tool which doesn't analyze things very far? Or is there
> an actual problem?
>
> And why does this have a Fixes: tag and the expectation to be included
> as a bug fix to stable kernels?
>
> And why is the author of the blamed patch even CCed only at v5?!

Sorry to know this, I ran the script and there I did not find your name.

./scripts/get_maintainer.pl drivers/net/ethernet/broadcom/bcmsysport.c
Florian Fainelli <florian.fainelli@broadcom.com> (supporter:BROADCOM
SYSTEMPORT ETHERNET DRIVER)
Broadcom internal kernel review list
<bcm-kernel-feedback-list@broadcom.com> (reviewer:BROADCOM SYSTEMPORT
ETHERNET DRIVER)
"David S. Miller" <davem@davemloft.net> (maintainer:NETWORKING DRIVERS)
Eric Dumazet <edumazet@google.com> (maintainer:NETWORKING DRIVERS)
Jakub Kicinski <kuba@kernel.org> (maintainer:NETWORKING DRIVERS)
Paolo Abeni <pabeni@redhat.com> (maintainer:NETWORKING DRIVERS)
netdev@vger.kernel.org (open list:BROADCOM SYSTEMPORT ETHERNET DRIVER)
linux-kernel@vger.kernel.org (open list)

Thank you so much for your time and effort , special thanks to Simon
for everything ,thanks Vladimir for the way you explained. and thanks
Florian for your help.

Best regards,
Dipendra Khadka

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

[Vladimir Oltean]

On Mon, Sep 30, 2024 at 11:52:45PM +0545, Dipendra Khadka wrote:
> > And why is the author of the blamed patch even CCed only at v5?!
> 
> Sorry to know this, I ran the script and there I did not find your name.
> 
> ./scripts/get_maintainer.pl drivers/net/ethernet/broadcom/bcmsysport.c
> Florian Fainelli <florian.fainelli@broadcom.com> (supporter:BROADCOM SYSTEMPORT ETHERNET DRIVER)
> Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com> (reviewer:BROADCOM SYSTEMPORT ETHERNET DRIVER)
> "David S. Miller" <davem@davemloft.net> (maintainer:NETWORKING DRIVERS)
> Eric Dumazet <edumazet@google.com> (maintainer:NETWORKING DRIVERS)
> Jakub Kicinski <kuba@kernel.org> (maintainer:NETWORKING DRIVERS)
> Paolo Abeni <pabeni@redhat.com> (maintainer:NETWORKING DRIVERS)
> netdev@vger.kernel.org (open list:BROADCOM SYSTEMPORT ETHERNET DRIVER)
> linux-kernel@vger.kernel.org (open list)

It's in the question you ask. Am I a maintainer of bcmsysport? No, and
I haven't made significant contributions on it either. But if you run
get_maintainer.pl on the _patch_ file that you will run through git
send-email, my name will be listed (the "--fixes" option defaults to 1).

The netdev CI also runs get_maintainers.pl on the actual patch, and that
triggers one of its red flags: "1 blamed authors not CCed: vladimir.oltean@nxp.com"
https://patchwork.kernel.org/project/netdevbpf/patch/20240926160513.7252-1-kdipendra88@gmail.com/

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

[Dipendra Khadka]

Hi,
On Tue, 1 Oct 2024 at 02:17, Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
>
> On Mon, Sep 30, 2024 at 11:52:45PM +0545, Dipendra Khadka wrote:
> > > And why is the author of the blamed patch even CCed only at v5?!
> >
> > Sorry to know this, I ran the script and there I did not find your name.
> >
> > ./scripts/get_maintainer.pl drivers/net/ethernet/broadcom/bcmsysport.c
> > Florian Fainelli <florian.fainelli@broadcom.com> (supporter:BROADCOM SYSTEMPORT ETHERNET DRIVER)
> > Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com> (reviewer:BROADCOM SYSTEMPORT ETHERNET DRIVER)
> > "David S. Miller" <davem@davemloft.net> (maintainer:NETWORKING DRIVERS)
> > Eric Dumazet <edumazet@google.com> (maintainer:NETWORKING DRIVERS)
> > Jakub Kicinski <kuba@kernel.org> (maintainer:NETWORKING DRIVERS)
> > Paolo Abeni <pabeni@redhat.com> (maintainer:NETWORKING DRIVERS)
> > netdev@vger.kernel.org (open list:BROADCOM SYSTEMPORT ETHERNET DRIVER)
> > linux-kernel@vger.kernel.org (open list)
>
> It's in the question you ask. Am I a maintainer of bcmsysport? No, and
> I haven't made significant contributions on it either. But if you run
> get_maintainer.pl on the _patch_ file that you will run through git
> send-email, my name will be listed (the "--fixes" option defaults to 1).
>

Oh, thank you for this. I only used to run get_maintainers.pl on the
file which got changed. I will run on the patch file as well from now.

> The netdev CI also runs get_maintainers.pl on the actual patch, and that
> triggers one of its red flags: "1 blamed authors not CCed: vladimir.oltean@nxp.com"
> https://patchwork.kernel.org/project/netdevbpf/patch/20240926160513.7252-1-kdipendra88@gmail.com/

Best regards,
Dipendra Khadka