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Subject: Re: [PATCH] net: macb: fix NULL dereference due to no pcs_config
 method
To:     Parshuram Thombare <pthombar@cadence.com>, <kuba@kernel.org>,
        <linux-arm-kernel@lists.infradead.org>, <netdev@vger.kernel.org>,
        <linux@armlinux.org.uk>
CC:     <Claudiu.Beznea@microchip.com>, <Santiago.Esteban@microchip.com>,
        <andrew@lunn.ch>, <davem@davemloft.net>,
        <linux-kernel@vger.kernel.org>, <harini.katakam@xilinx.com>,
        <michal.simek@xilinx.com>
References: <1604587039-5646-1-git-send-email-pthombar@cadence.com>
From:   Nicolas Ferre <nicolas.ferre@microchip.com>
Organization: microchip
Message-ID: <6873cf12-456b-c121-037b-d2c5a6138cb3@microchip.com>
Date:   Thu, 5 Nov 2020 16:22:18 +0100
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On 05/11/2020 at 15:37, Parshuram Thombare wrote:
> This patch fixes NULL pointer dereference due to NULL pcs_config
> in pcs_ops.
> 
> Fixes: e4e143e26ce8 ("net: macb: add support for high speed interface")

What is this tag? In linux-next? As patch is not yet in Linus' tree, you 
cannot refer to it like this.

> Reported-by: Nicolas Ferre <Nicolas.Ferre@microchip.com>
> Link: https://lkml.org/lkml/2020/11/4/482

You might need to change this to a "lore" link:
https://lore.kernel.org/netdev/2db854c7-9ffb-328a-f346-f68982723d29@microchip.com/

> Signed-off-by: Parshuram Thombare <pthombar@cadence.com>

This fix looks a bit weird to me. What about proposing a patch to 
Russell like the chunk that you already identified in function 
phylink_major_config()?


> ---
>   drivers/net/ethernet/cadence/macb_main.c | 17 +++++++++++++++--
>   1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index b7bc160..130a5af 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -633,6 +633,15 @@ static void macb_pcs_an_restart(struct phylink_pcs *pcs)
>          /* Not supported */
>   }
> 
> +static int macb_pcs_config(struct phylink_pcs *pcs,
> +                          unsigned int mode,
> +                          phy_interface_t interface,
> +                          const unsigned long *advertising,
> +                          bool permit_pause_to_mac)
> +{
> +       return 0;
> +}

Russell, is the requirement for this void function intended?

> +
>   static const struct phylink_pcs_ops macb_phylink_usx_pcs_ops = {
>          .pcs_get_state = macb_usx_pcs_get_state,
>          .pcs_config = macb_usx_pcs_config,
> @@ -642,6 +651,7 @@ static const struct phylink_pcs_ops macb_phylink_usx_pcs_ops = {
>   static const struct phylink_pcs_ops macb_phylink_pcs_ops = {
>          .pcs_get_state = macb_pcs_get_state,
>          .pcs_an_restart = macb_pcs_an_restart,
> +       .pcs_config = macb_pcs_config,
>   };
> 
>   static void macb_mac_config(struct phylink_config *config, unsigned int mode,
> @@ -776,10 +786,13 @@ static int macb_mac_prepare(struct phylink_config *config, unsigned int mode,
> 
>          if (interface == PHY_INTERFACE_MODE_10GBASER)
>                  bp->phylink_pcs.ops = &macb_phylink_usx_pcs_ops;
> -       else
> +       else if (interface == PHY_INTERFACE_MODE_SGMII)
>                  bp->phylink_pcs.ops = &macb_phylink_pcs_ops;

Do you confirm that all SGMII type interfaces need phylink_pcs.ops?

> +       else
> +               bp->phylink_pcs.ops = NULL;
> 
> -       phylink_set_pcs(bp->phylink, &bp->phylink_pcs);
> +       if (bp->phylink_pcs.ops)
> +               phylink_set_pcs(bp->phylink, &bp->phylink_pcs);
> 
>          return 0;
>   }

Regards,
   Nicolas

-- 
Nicolas Ferre