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

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Date:   Tue, 15 Nov 2022 14:52:51 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <vladimir.oltean@....com>, netdev@...r.kernel.org
Cc:     Andrew Lunn <andrew@...n.ch>, Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net] net: dsa: don't leak tagger-owned storage on switch
 driver unbind

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@....com>

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