netdev - Re: [PATCH net-next v14 12/13] net: ethtool: strset: Allow querying phy stats by index

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Message-ID: <20240703201851.GT598357@kernel.org>
Date: Wed, 3 Jul 2024 21:18:51 +0100
From: Simon Horman <horms@...nel.org>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
	Andrew Lunn <andrew@...n.ch>, Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Russell King <linux@...linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Herve Codina <herve.codina@...tlin.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Köry Maincent <kory.maincent@...tlin.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Marek Behún <kabel@...nel.org>,
	Piergiorgio Beruto <piergiorgio.beruto@...il.com>,
	Oleksij Rempel <o.rempel@...gutronix.de>,
	Nicolò Veronese <nicveronese@...il.com>,
	mwojtas@...omium.org, Nathan Chancellor <nathan@...nel.org>,
	Antoine Tenart <atenart@...nel.org>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: Re: [PATCH net-next v14 12/13] net: ethtool: strset: Allow querying
 phy stats by index

On Wed, Jul 03, 2024 at 08:55:15AM +0200, Maxime Chevallier wrote:
> Hello Simon,
> 
> On Tue, 2 Jul 2024 11:54:11 +0100
> Simon Horman <horms@...nel.org> wrote:
> 
> > On Mon, Jul 01, 2024 at 03:17:58PM +0200, Maxime Chevallier wrote:
> > > The ETH_SS_PHY_STATS command gets PHY statistics. Use the phydev pointer
> > > from the ethnl request to allow query phy stats from each PHY on the
> > > link.
> > > 
> > > Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
> > > ---
> > >  net/ethtool/strset.c | 24 +++++++++++++++++-------
> > >  1 file changed, 17 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/net/ethtool/strset.c b/net/ethtool/strset.c  
> > 
> > ...
> > 
> > > @@ -279,6 +280,8 @@ static int strset_prepare_data(const struct ethnl_req_info *req_base,
> > >  	const struct strset_req_info *req_info = STRSET_REQINFO(req_base);
> > >  	struct strset_reply_data *data = STRSET_REPDATA(reply_base);
> > >  	struct net_device *dev = reply_base->dev;
> > > +	struct nlattr **tb = info->attrs;  
> > 
> > Hi Maxime,
> > 
> > Elsewhere in this function it is assumed that info may be NULL.
> > But here it is dereferenced unconditionally.
> 
> Hmm in almst all netlink commands we do dereference the genl_info *info
> pointer without checks.
> 
> I've looked into net/netlink/genetlink.c to backtrack call-sites and it
> looks to be that indeed info can't be NULL (either populated from
> genl_start() or genl_family_rcv_msg_doit(). Maybe Jakub can confirm
> this ?
> 
> If what I say above is correct, I can include a small patch to remove
> the un-necessary check that makes smatch think the genl_info pointer can
> be NULL.

Thanks for following up.
Assuming that is true (I did not check yet) then I agree.
And I don't think such a change needs to block this patchset.