If a port joins a bridge that it can't offload, it will fallback to
standalone mode and software bridging. In this case, we never want to
offload any FDB entries to hardware either.

Previously, for host addresses, we would eventually end up in
dsa_port_bridge_host_fdb_add, which would unconditionally dereference
dp->bridge and cause a segfault.

Fixes: c26933639b54 ("net: dsa: request drivers to perform FDB isolation")
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
---
 net/dsa/slave.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index f9cecda791d5..d24b6bf845c1 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -2847,6 +2847,9 @@ static int dsa_slave_fdb_event(struct net_device *dev,
 	if (ctx && ctx != dp)
 		return 0;
 
+	if (!dp->bridge)
+		return 0;
+
 	if (switchdev_fdb_is_dynamically_learned(fdb_info)) {
 		if (dsa_port_offloads_bridge_port(dp, orig_dev))
 			return 0;
-- 
2.25.1

On Wed, Mar 16, 2022 at 12:30:33AM +0100, Tobias Waldekranz wrote:
> If a port joins a bridge that it can't offload, it will fallback to
> standalone mode and software bridging. In this case, we never want to
> offload any FDB entries to hardware either.
> 
> Previously, for host addresses, we would eventually end up in
> dsa_port_bridge_host_fdb_add, which would unconditionally dereference
> dp->bridge and cause a segfault.
> 
> Fixes: c26933639b54 ("net: dsa: request drivers to perform FDB isolation")
> Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
> ---

Reviewed-by: Vladimir Oltean <olteanv@gmail.com>

>  net/dsa/slave.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index f9cecda791d5..d24b6bf845c1 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -2847,6 +2847,9 @@ static int dsa_slave_fdb_event(struct net_device *dev,
>  	if (ctx && ctx != dp)
>  		return 0;
>  
> +	if (!dp->bridge)
> +		return 0;
> +
>  	if (switchdev_fdb_is_dynamically_learned(fdb_info)) {
>  		if (dsa_port_offloads_bridge_port(dp, orig_dev))
>  			return 0;
> -- 
> 2.25.1
>

On 3/15/22 4:30 PM, Tobias Waldekranz wrote:
> If a port joins a bridge that it can't offload, it will fallback to
> standalone mode and software bridging. In this case, we never want to
> offload any FDB entries to hardware either.
> 
> Previously, for host addresses, we would eventually end up in
> dsa_port_bridge_host_fdb_add, which would unconditionally dereference
> dp->bridge and cause a segfault.
> 
> Fixes: c26933639b54 ("net: dsa: request drivers to perform FDB isolation")
> Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 16 Mar 2022 00:30:33 +0100 you wrote:
> If a port joins a bridge that it can't offload, it will fallback to
> standalone mode and software bridging. In this case, we never want to
> offload any FDB entries to hardware either.
> 
> Previously, for host addresses, we would eventually end up in
> dsa_port_bridge_host_fdb_add, which would unconditionally dereference
> dp->bridge and cause a segfault.
> 
> [...]

Here is the summary with links:
  - [v2,net-next] net: dsa: Never offload FDB entries on standalone ports
    https://git.kernel.org/netdev/net-next/c/a860352e9dd0

You are awesome, thank you!
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