linux-kernel - Re: [PATCH net v3] net: dsa: Check existence of .port_mdb

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Date:   Sun, 11 Aug 2019 21:37:40 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     wens@...nel.org
Cc:     andrew@...n.ch, vivien.didelot@...il.com, f.fainelli@...il.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3] net: dsa: Check existence of .port_mdb_add
 callback before calling it

From: Chen-Yu Tsai <wens@...nel.org>
Date: Sun, 11 Aug 2019 22:18:25 +0800

> From: Chen-Yu Tsai <wens@...e.org>
> 
> The dsa framework has optional .port_mdb_{prepare,add,del} callback fields
> for drivers to handle multicast database entries. When adding an entry, the
> framework goes through a prepare phase, then a commit phase. Drivers not
> providing these callbacks should be detected in the prepare phase.
> 
> DSA core may still bypass the bridge layer and call the dsa_port_mdb_add
> function directly with no prepare phase or no switchdev trans object,
> and the framework ends up calling an undefined .port_mdb_add callback.
> This results in a NULL pointer dereference, as shown in the log below.
> 
> The other functions seem to be properly guarded. Do the same for
> .port_mdb_add in dsa_switch_mdb_add_bitmap() as well.
 ...
> Fixes: e6db98db8a95 ("net: dsa: add switch mdb bitmap functions")
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>

Applied and queued up for -stable, thanks.