[PATCH] net: bridge: add missing NULL checks

[PATCH] net: bridge: add missing NULL checks

[Laszlo Toth]

br_port_get_rtnl() can return NULL

Signed-off-by: Laszlo Toth <laszlth@gmail.com>
---
 net/bridge/br_netlink.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 015f465c..cbec11f 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -939,14 +939,17 @@ static int br_port_slave_changelink(struct net_device *brdev,
 				    struct nlattr *data[],
 				    struct netlink_ext_ack *extack)
 {
+	struct net_bridge_port *port = br_port_get_rtnl(dev);
 	struct net_bridge *br = netdev_priv(brdev);
 	int ret;
 
 	if (!data)
 		return 0;
+	if (!port)
+		return -EINVAL;
 
 	spin_lock_bh(&br->lock);
-	ret = br_setport(br_port_get_rtnl(dev), data);
+	ret = br_setport(port, data);
 	spin_unlock_bh(&br->lock);
 
 	return ret;
@@ -956,7 +959,12 @@ static int br_port_fill_slave_info(struct sk_buff *skb,
 				   const struct net_device *brdev,
 				   const struct net_device *dev)
 {
-	return br_port_fill_attrs(skb, br_port_get_rtnl(dev));
+	struct net_bridge_port *port = br_port_get_rtnl(dev);
+
+	if (!port)
+		return -EINVAL;
+
+	return br_port_fill_attrs(skb, port);
 }
 
 static size_t br_port_get_slave_size(const struct net_device *brdev,
-- 
2.7.4

Re: [PATCH] net: bridge: add missing NULL checks

[Nikolay Aleksandrov]

On 08/04/18 20:49, Laszlo Toth wrote:
> br_port_get_rtnl() can return NULL
> 
> Signed-off-by: Laszlo Toth <laszlth@gmail.com>
> ---
>   net/bridge/br_netlink.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 

Nacked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
More below.

> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> index 015f465c..cbec11f 100644
> --- a/net/bridge/br_netlink.c
> +++ b/net/bridge/br_netlink.c
> @@ -939,14 +939,17 @@ static int br_port_slave_changelink(struct net_device *brdev,
>   				    struct nlattr *data[],
>   				    struct netlink_ext_ack *extack)
>   {
> +	struct net_bridge_port *port = br_port_get_rtnl(dev);
>   	struct net_bridge *br = netdev_priv(brdev);
>   	int ret;
>   
>   	if (!data)
>   		return 0;
> +	if (!port)
> +		return -EINVAL;
>   

If we're here, it means the master device of dev is a bridge => dev is a bridge port,
since we're running with RTNL that cannot change, so this check is unnecessary.

Have you actually hit a bug with this code ?

>   	spin_lock_bh(&br->lock);
> -	ret = br_setport(br_port_get_rtnl(dev), data);
> +	ret = br_setport(port, data);
>   	spin_unlock_bh(&br->lock);
>   
>   	return ret;
> @@ -956,7 +959,12 @@ static int br_port_fill_slave_info(struct sk_buff *skb,
>   				   const struct net_device *brdev,
>   				   const struct net_device *dev)
>   {
> -	return br_port_fill_attrs(skb, br_port_get_rtnl(dev));
> +	struct net_bridge_port *port = br_port_get_rtnl(dev);
> +
> +	if (!port)
> +		return -EINVAL;
> +
> +	return br_port_fill_attrs(skb, port);

Same rationale here, fill_slave_info is called via a master device's ops
under RTNL, which means dev is a bridge port and that also cannot change.

If you have hit a bug with this code, can we see the trace ?
The problem might be elsewhere.

Thanks,
  Nik

>   }
>   
>   static size_t br_port_get_slave_size(const struct net_device *brdev,
> 

Re: [PATCH] net: bridge: add missing NULL checks

[Laszlo Toth]

On Mon, Apr 09, 2018 at 01:25:41AM +0300, Nikolay Aleksandrov wrote:
> On 08/04/18 20:49, Laszlo Toth wrote:
> >br_port_get_rtnl() can return NULL
> >
> >Signed-off-by: Laszlo Toth <laszlth@gmail.com>
> >---
> >  net/bridge/br_netlink.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> >
> 
> Nacked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
> More below.
> 
> >diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> >index 015f465c..cbec11f 100644
> >--- a/net/bridge/br_netlink.c
> >+++ b/net/bridge/br_netlink.c
> >@@ -939,14 +939,17 @@ static int br_port_slave_changelink(struct net_device *brdev,
> >  				    struct nlattr *data[],
> >  				    struct netlink_ext_ack *extack)
> >  {
> >+	struct net_bridge_port *port = br_port_get_rtnl(dev);
> >  	struct net_bridge *br = netdev_priv(brdev);
> >  	int ret;
> >  	if (!data)
> >  		return 0;
> >+	if (!port)
> >+		return -EINVAL;
> 
> If we're here, it means the master device of dev is a bridge => dev is a bridge port,
> since we're running with RTNL that cannot change, so this check is unnecessary.
> 
> Have you actually hit a bug with this code ?
> 
> >  	spin_lock_bh(&br->lock);
> >-	ret = br_setport(br_port_get_rtnl(dev), data);
> >+	ret = br_setport(port, data);
> >  	spin_unlock_bh(&br->lock);
> >  	return ret;
> >@@ -956,7 +959,12 @@ static int br_port_fill_slave_info(struct sk_buff *skb,
> >  				   const struct net_device *brdev,
> >  				   const struct net_device *dev)
> >  {
> >-	return br_port_fill_attrs(skb, br_port_get_rtnl(dev));
> >+	struct net_bridge_port *port = br_port_get_rtnl(dev);
> >+
> >+	if (!port)
> >+		return -EINVAL;
> >+
> >+	return br_port_fill_attrs(skb, port);
> 
> Same rationale here, fill_slave_info is called via a master device's ops
> under RTNL, which means dev is a bridge port and that also cannot change.
> 
> If you have hit a bug with this code, can we see the trace ?
> The problem might be elsewhere.

There was a NULL dereference in br_port_fill_attrs(), but on a much
older release w/ a probably buggy and custom driver,
so there is no real problem to trace.
Anyway I thought I'd make a quick patch from it, but you're right,
it's pointless to validate twice. 

Please just ignore the patch.

Laszlo

> 
> Thanks,
>  Nik
> 
> >  }
> >  static size_t br_port_get_slave_size(const struct net_device *brdev,
> >
>