linux-kernel - Re: [PATCH] net: phy: fix phy_read_poll_timeout argument type in genphy

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Date: Wed, 13 Mar 2024 19:12:59 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Nikita Kiryushin <kiryushin@...ud.ru>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Oleksij Rempel <o.rempel@...gutronix.de>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: phy: fix phy_read_poll_timeout argument type in
 genphy_loopback

On Wed, Mar 13, 2024 at 09:13:23PM +0300, Nikita Kiryushin wrote:
> read_poll_timeout inside phy_read_poll_timeout can set val negative
> in some cases (for example, __mdiobus_read inside phy_read can return
> -EOPNOTSUPP).
> 
> Supposedly, commit 4ec732951702 ("net: phylib: fix
> phy_read*_poll_timeout()")
> should fix problems with wrong-signed vals, but I do not see how
> as val is sent to phy_read as is and __val = phy_read (not val)
> is checked for sign.
> 
> Change val type for signed to allow better error handling as done in other
> phy_read_poll_timeout callers. This will not fix any error handling
> by itself, but allows, for example, to modify cond with appropriate
> sign check or check resulting val separately.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 014068dcb5b1 ("net: phy: genphy_loopback: add link speed
> configuration")

Fixes lines must not be wrapped.

> Signed-off-by: Nikita Kiryushin <kiryushin@...ud.ru>
> ---
>  drivers/net/phy/phy_device.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 8297ef681bf5..6c6ec9475709 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -2831,8 +2831,8 @@ EXPORT_SYMBOL(genphy_resume);
>  int genphy_loopback(struct phy_device *phydev, bool enable)
>  {
>  	if (enable) {
> -		u16 val, ctl = BMCR_LOOPBACK;
> -		int ret;
> +		u16 ctl = BMCR_LOOPBACK;
> +		int ret, val;
>   		ctl |= mii_bmcr_encode_fixed(phydev->speed, phydev->duplex);
>  -- 2.34.1

The patch seems broken - blank lines appear to be missing.

I think the change itself is correct however - "val" passed into
phy_read_poll_timeout() must be signed.

Lastly, as you need to indicate which tree your patch is targetting,
which is done via the subject line prefix. As this is in mainline, then
[PATCH net] would be the correct prefix.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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