[PATCH net] net: dsa: don't leak tagger-owned storage on switch driver unbind

[PATCH net] net: dsa: don't leak tagger-owned storage on switch driver unbind

[Vladimir Oltean]

In the initial commit dc452a471dba ("net: dsa: introduce tagger-owned
storage for private and shared data"), we had a call to
tag_ops->disconnect(dst) issued from dsa_tree_free(), which is called at
tree teardown time.

There were problems with connecting to a switch tree as a whole, so this
got reworked to connecting to individual switches within the tree. In
this process, tag_ops->disconnect(ds) was made to be called only from
switch.c (cross-chip notifiers emitted as a result of dynamic tag proto
changes), but the normal driver teardown code path wasn't replaced with
anything.

Solve this problem by adding a function that does the opposite of
dsa_switch_setup_tag_protocol(), which is called from the equivalent
spot in dsa_switch_teardown(). The positioning here also ensures that we
won't have any use-after-free in tagging protocol (*rcv) ops, since the
teardown sequence is as follows:

dsa_tree_teardown
-> dsa_tree_teardown_master
   -> dsa_master_teardown
      -> unsets master->dsa_ptr, making no further packets match the
         ETH_P_XDSA packet type handler
-> dsa_tree_teardown_ports
   -> dsa_port_teardown
      -> dsa_slave_destroy
         -> unregisters DSA net devices, there is even a synchronize_net()
            in unregister_netdevice_many()
-> dsa_tree_teardown_switches
   -> dsa_switch_teardown
      -> dsa_switch_teardown_tag_protocol
         -> finally frees the tagger-owned storage

Fixes: 7f2973149c22 ("net: dsa: make tagging protocols connect to individual switches from a tree")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 net/dsa/dsa2.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index b80dbd02e154..12145c852902 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -855,6 +855,14 @@ static int dsa_switch_setup_tag_protocol(struct dsa_switch *ds)
 	return err;
 }
 
+static void dsa_switch_teardown_tag_protocol(struct dsa_switch *ds)
+{
+	const struct dsa_device_ops *tag_ops = ds->dst->tag_ops;
+
+	if (tag_ops->disconnect)
+		tag_ops->disconnect(ds);
+}
+
 static int dsa_switch_setup(struct dsa_switch *ds)
 {
 	struct dsa_devlink_priv *dl_priv;
@@ -944,6 +952,8 @@ static void dsa_switch_teardown(struct dsa_switch *ds)
 		ds->slave_mii_bus = NULL;
 	}
 
+	dsa_switch_teardown_tag_protocol(ds);
+
 	if (ds->ops->teardown)
 		ds->ops->teardown(ds);
 
-- 
2.34.1

Re: [PATCH net] net: dsa: don't leak tagger-owned storage on switch driver unbind

[Saeed Mahameed]

On 14 Nov 16:35, Vladimir Oltean wrote:
>In the initial commit dc452a471dba ("net: dsa: introduce tagger-owned
>storage for private and shared data"), we had a call to
>tag_ops->disconnect(dst) issued from dsa_tree_free(), which is called at
>tree teardown time.
>
>There were problems with connecting to a switch tree as a whole, so this
>got reworked to connecting to individual switches within the tree. In
>this process, tag_ops->disconnect(ds) was made to be called only from
>switch.c (cross-chip notifiers emitted as a result of dynamic tag proto
>changes), but the normal driver teardown code path wasn't replaced with
>anything.
>
>Solve this problem by adding a function that does the opposite of
>dsa_switch_setup_tag_protocol(), which is called from the equivalent
>spot in dsa_switch_teardown(). The positioning here also ensures that we
>won't have any use-after-free in tagging protocol (*rcv) ops, since the
>teardown sequence is as follows:
>
>dsa_tree_teardown
>-> dsa_tree_teardown_master
>   -> dsa_master_teardown
>      -> unsets master->dsa_ptr, making no further packets match the
>         ETH_P_XDSA packet type handler
>-> dsa_tree_teardown_ports
>   -> dsa_port_teardown
>      -> dsa_slave_destroy
>         -> unregisters DSA net devices, there is even a synchronize_net()
>            in unregister_netdevice_many()
>-> dsa_tree_teardown_switches
>   -> dsa_switch_teardown
>      -> dsa_switch_teardown_tag_protocol
>         -> finally frees the tagger-owned storage
>
>Fixes: 7f2973149c22 ("net: dsa: make tagging protocols connect to individual switches from a tree")
>Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Saeed Mahameed <saeed@kernel.org>

Re: [PATCH net] net: dsa: don't leak tagger-owned storage on switch driver unbind

[Florian Fainelli]

On 11/14/22 06:35, Vladimir Oltean wrote:
> In the initial commit dc452a471dba ("net: dsa: introduce tagger-owned
> storage for private and shared data"), we had a call to
> tag_ops->disconnect(dst) issued from dsa_tree_free(), which is called at
> tree teardown time.
> 
> There were problems with connecting to a switch tree as a whole, so this
> got reworked to connecting to individual switches within the tree. In
> this process, tag_ops->disconnect(ds) was made to be called only from
> switch.c (cross-chip notifiers emitted as a result of dynamic tag proto
> changes), but the normal driver teardown code path wasn't replaced with
> anything.
> 
> Solve this problem by adding a function that does the opposite of
> dsa_switch_setup_tag_protocol(), which is called from the equivalent
> spot in dsa_switch_teardown(). The positioning here also ensures that we
> won't have any use-after-free in tagging protocol (*rcv) ops, since the
> teardown sequence is as follows:
> 
> dsa_tree_teardown
> -> dsa_tree_teardown_master
>     -> dsa_master_teardown
>        -> unsets master->dsa_ptr, making no further packets match the
>           ETH_P_XDSA packet type handler
> -> dsa_tree_teardown_ports
>     -> dsa_port_teardown
>        -> dsa_slave_destroy
>           -> unregisters DSA net devices, there is even a synchronize_net()
>              in unregister_netdevice_many()
> -> dsa_tree_teardown_switches
>     -> dsa_switch_teardown
>        -> dsa_switch_teardown_tag_protocol
>           -> finally frees the tagger-owned storage
> 
> Fixes: 7f2973149c22 ("net: dsa: make tagging protocols connect to individual switches from a tree")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

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

Re: [PATCH net] net: dsa: don't leak tagger-owned storage on switch driver unbind

[patchwork-bot+netdevbpf]

Hello:

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

On Mon, 14 Nov 2022 16:35:51 +0200 you wrote:
> In the initial commit dc452a471dba ("net: dsa: introduce tagger-owned
> storage for private and shared data"), we had a call to
> tag_ops->disconnect(dst) issued from dsa_tree_free(), which is called at
> tree teardown time.
> 
> There were problems with connecting to a switch tree as a whole, so this
> got reworked to connecting to individual switches within the tree. In
> this process, tag_ops->disconnect(ds) was made to be called only from
> switch.c (cross-chip notifiers emitted as a result of dynamic tag proto
> changes), but the normal driver teardown code path wasn't replaced with
> anything.
> 
> [...]

Here is the summary with links:
  - [net] net: dsa: don't leak tagger-owned storage on switch driver unbind
    https://git.kernel.org/netdev/net/c/4e0c19fcb8b5

You are awesome, thank you!
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