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Message-ID: <905b0b48-5184-3b11-2f78-e99834dbc38a@oracle.com>
Date: Tue, 5 May 2020 11:37:12 +0530
From: Allen <allen.pais@...cle.com>
To: Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Cc: Andrew Lunn <andrew@...n.ch>,
Vivien Didelot <vivien.didelot@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: dsa: Do not leave DSA master with NULL
netdev_ops
> When ndo_get_phys_port_name() for the CPU port was added we introduced
> an early check for when the DSA master network device in
> dsa_master_ndo_setup() already implements ndo_get_phys_port_name(). When
> we perform the teardown operation in dsa_master_ndo_teardown() we would
> not be checking that cpu_dp->orig_ndo_ops was successfully allocated and
> non-NULL initialized.
>
> With network device drivers such as virtio_net, this leads to a NPD as
> soon as the DSA switch hanging off of it gets torn down because we are
> now assigning the virtio_net device's netdev_ops a NULL pointer.
>
> Fixes: da7b9e9b00d4 ("net: dsa: Add ndo_get_phys_port_name() for CPU port")
> Reported-by: Allen Pais <allen.pais@...cle.com>
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
Tested-by: Allen Pais <allen.pais@...cle.com>
Thank you Florain.
> ---
> net/dsa/master.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/dsa/master.c b/net/dsa/master.c
> index b5c535af63a3..a621367c6e8c 100644
> --- a/net/dsa/master.c
> +++ b/net/dsa/master.c
> @@ -289,7 +289,8 @@ static void dsa_master_ndo_teardown(struct net_device *dev)
> {
> struct dsa_port *cpu_dp = dev->dsa_ptr;
>
> - dev->netdev_ops = cpu_dp->orig_ndo_ops;
> + if (cpu_dp->orig_ndo_ops)
> + dev->netdev_ops = cpu_dp->orig_ndo_ops;
> cpu_dp->orig_ndo_ops = NULL;
> }
>
>
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