[PATCH net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll_start

[PATCH net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll_start

[Vladimir Oltean]

The current link mode of the phylink instance may not require an
attached PCS. However, phylink_major_config() unconditionally
dereferences this potentially NULL pointer when restarting the link poll
timer, which will panic the kernel.

Fix the problem by checking whether a PCS exists in phylink_pcs_poll_start(),
otherwise do nothing. The code prior to the blamed patch also only
looked at pcs->poll within an "if (pcs)" block.

Fixes: bfac8c490d60 ("net: phylink: disable PCS polling over major configuration")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 drivers/net/phy/phylink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 1a7550f5fdf5..48f0b9b39491 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -766,7 +766,7 @@ static void phylink_pcs_poll_stop(struct phylink *pl)
 
 static void phylink_pcs_poll_start(struct phylink *pl)
 {
-	if (pl->pcs->poll && pl->cfg_link_an_mode == MLO_AN_INBAND)
+	if (pl->pcs && pl->pcs->poll && pl->cfg_link_an_mode == MLO_AN_INBAND)
 		mod_timer(&pl->link_poll, jiffies + HZ);
 }
 
-- 
2.25.1

Re: [PATCH net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll_start

[Russell King (Oracle)]

On Wed, Jun 29, 2022 at 10:33:58PM +0300, Vladimir Oltean wrote:
> The current link mode of the phylink instance may not require an
> attached PCS. However, phylink_major_config() unconditionally
> dereferences this potentially NULL pointer when restarting the link poll
> timer, which will panic the kernel.
> 
> Fix the problem by checking whether a PCS exists in phylink_pcs_poll_start(),
> otherwise do nothing. The code prior to the blamed patch also only
> looked at pcs->poll within an "if (pcs)" block.
> 
> Fixes: bfac8c490d60 ("net: phylink: disable PCS polling over major configuration")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Thanks.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

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Re: [PATCH net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll_start

[Gerhard Engleder]

On 29.06.22 21:42, Russell King (Oracle) wrote:
> On Wed, Jun 29, 2022 at 10:33:58PM +0300, Vladimir Oltean wrote:
>> The current link mode of the phylink instance may not require an
>> attached PCS. However, phylink_major_config() unconditionally
>> dereferences this potentially NULL pointer when restarting the link poll
>> timer, which will panic the kernel.
>>
>> Fix the problem by checking whether a PCS exists in phylink_pcs_poll_start(),
>> otherwise do nothing. The code prior to the blamed patch also only
>> looked at pcs->poll within an "if (pcs)" block.
>>
>> Fixes: bfac8c490d60 ("net: phylink: disable PCS polling over major configuration")
>> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> Thanks.
>
> Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
>
Fixes the problem on my side.

Tested-by: Gerhard Engleder <gerhard@engleder-embedded.com>

Re: [PATCH net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll_start

[Michael Walle]

> The current link mode of the phylink instance may not require an
> attached PCS. However, phylink_major_config() unconditionally
> dereferences this potentially NULL pointer when restarting the link poll
> timer, which will panic the kernel.
> 
> Fix the problem by checking whether a PCS exists in phylink_pcs_poll_start(),
> otherwise do nothing. The code prior to the blamed patch also only
> looked at pcs->poll within an "if (pcs)" block.
> 
> Fixes: bfac8c490d60 ("net: phylink: disable PCS polling over major configuration")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Tested-by: Michael Walle <michael@walle.cc> # on kontron-kbox-a-230-ls

-michael

Re: [PATCH net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll_start

[Nicolas Ferre]

Vladimir, Russell,

On 29/06/2022 at 21:33, Vladimir Oltean wrote:
> The current link mode of the phylink instance may not require an
> attached PCS. However, phylink_major_config() unconditionally
> dereferences this potentially NULL pointer when restarting the link poll
> timer, which will panic the kernel.
> 
> Fix the problem by checking whether a PCS exists in phylink_pcs_poll_start(),
> otherwise do nothing. The code prior to the blamed patch also only
> looked at pcs->poll within an "if (pcs)" block.
> 
> Fixes: bfac8c490d60 ("net: phylink: disable PCS polling over major configuration")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
>   drivers/net/phy/phylink.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> index 1a7550f5fdf5..48f0b9b39491 100644
> --- a/drivers/net/phy/phylink.c
> +++ b/drivers/net/phy/phylink.c
> @@ -766,7 +766,7 @@ static void phylink_pcs_poll_stop(struct phylink *pl)
>   
>   static void phylink_pcs_poll_start(struct phylink *pl)
>   {
> -	if (pl->pcs->poll && pl->cfg_link_an_mode == MLO_AN_INBAND)
> +	if (pl->pcs && pl->pcs->poll && pl->cfg_link_an_mode == MLO_AN_INBAND)
>   		mod_timer(&pl->link_poll, jiffies + HZ);
>   }
>   

Fixes the NULL pointer on my boards:
Tested-by: Nicolas Ferre <nicolas.ferre@microchip.com> # on sam9x60ek

Best regards,
   Nicolas


-- 
Nicolas Ferre

Re: [PATCH net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll_start

[Russell King (Oracle)]

On Thu, Jun 30, 2022 at 03:46:54PM +0200, Nicolas Ferre wrote:
> Vladimir, Russell,
> 
> On 29/06/2022 at 21:33, Vladimir Oltean wrote:
> > The current link mode of the phylink instance may not require an
> > attached PCS. However, phylink_major_config() unconditionally
> > dereferences this potentially NULL pointer when restarting the link poll
> > timer, which will panic the kernel.
> > 
> > Fix the problem by checking whether a PCS exists in phylink_pcs_poll_start(),
> > otherwise do nothing. The code prior to the blamed patch also only
> > looked at pcs->poll within an "if (pcs)" block.
> > 
> > Fixes: bfac8c490d60 ("net: phylink: disable PCS polling over major configuration")
> > Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> > ---
> >   drivers/net/phy/phylink.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> > index 1a7550f5fdf5..48f0b9b39491 100644
> > --- a/drivers/net/phy/phylink.c
> > +++ b/drivers/net/phy/phylink.c
> > @@ -766,7 +766,7 @@ static void phylink_pcs_poll_stop(struct phylink *pl)
> >   static void phylink_pcs_poll_start(struct phylink *pl)
> >   {
> > -	if (pl->pcs->poll && pl->cfg_link_an_mode == MLO_AN_INBAND)
> > +	if (pl->pcs && pl->pcs->poll && pl->cfg_link_an_mode == MLO_AN_INBAND)
> >   		mod_timer(&pl->link_poll, jiffies + HZ);
> >   }
> 
> Fixes the NULL pointer on my boards:
> Tested-by: Nicolas Ferre <nicolas.ferre@microchip.com> # on sam9x60ek

Thanks all, hopefully it'll get applied to net-next soon.

Sadly, this slipped through my testing, as the only platform I have
access to at the moment always supplies a PCS (mvneta based) so there's
no way my testing would ever have caught this. Sorry for the problems.

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Re: [PATCH net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll_start

[patchwork-bot+netdevbpf]

Hello:

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

On Wed, 29 Jun 2022 22:33:58 +0300 you wrote:
> The current link mode of the phylink instance may not require an
> attached PCS. However, phylink_major_config() unconditionally
> dereferences this potentially NULL pointer when restarting the link poll
> timer, which will panic the kernel.
> 
> Fix the problem by checking whether a PCS exists in phylink_pcs_poll_start(),
> otherwise do nothing. The code prior to the blamed patch also only
> looked at pcs->poll within an "if (pcs)" block.
> 
> [...]

Here is the summary with links:
  - [net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll_start
    https://git.kernel.org/netdev/net-next/c/b7d78b46d5e8

You are awesome, thank you!
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