linux-kernel - Re: [PATCH net v2] broadcom: b44: prevent uninitialized value usage

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Message-ID: <CAOiHx=kSaA--VuQtTuWyUxx6PE5z-xu-H1wiUxXbMYM_e9+qJQ@mail.gmail.com>
Date: Fri, 5 Dec 2025 09:00:59 +0100
From: Jonas Gorski <jonas.gorski@...il.com>
To: Alexey Simakov <bigalex934@...il.com>
Cc: Michael Chan <michael.chan@...adcom.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	"John W. Linville" <linville@...driver.com>, Michael Buesch <mb@...sch.de>, linux-kernel@...r.kernel.org, 
	lvc-project@...uxtesting.org
Subject: Re: [PATCH net v2] broadcom: b44: prevent uninitialized value usage

On Fri, Dec 5, 2025 at 8:18 AM Alexey Simakov <bigalex934@...il.com> wrote:
>
> On execution path with raised B44_FLAG_EXTERNAL_PHY, b44_readphy()
> leaves bmcr value uninitialized and it is used later in the code.
>
> Add check of this flag at the beginning of the b44_nway_reset() and
> exit early of the function with restarting autonegotiation if an
> external PHY is used.
>
> Found by Linux Verification Center (linuxtesting.org) with Svace.
>
> Fixes: 753f492093da ("[B44]: port to native ssb support")
> Signed-off-by: Alexey Simakov <bigalex934@...il.com>
> ---
>
> v2 - add restarting of autonegotiations by phy_ethtool_nway_reset(),
> instead of returning with 0 code (suggested by Jonas Gorski).
>
> link to v1: https://lore.kernel.org/all/20251204052243.5824-1-bigalex934@gmail.com/
>
>  drivers/net/ethernet/broadcom/b44.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c
> index 0353359c3fe9..073d7d490d4b 100644
> --- a/drivers/net/ethernet/broadcom/b44.c
> +++ b/drivers/net/ethernet/broadcom/b44.c
> @@ -1789,6 +1789,9 @@ static int b44_nway_reset(struct net_device *dev)
>         u32 bmcr;
>         int r;
>
> +       if (bp->flags & B44_FLAG_EXTERNAL_PHY)
> +               return phy_ethtool_nway_reset(dev);

Thanks for double checking and not blindly copying my suggestion lol.
(phy_ethtool_nway_reset() takes a net_device *, not a phy_device *
...).

In that sense,

Reviewed-by: Jonas Gorski <jonas.gorski@...il.com>

Best regards,
Jonas