linux-kernel - Re: [PATCH 1/7] phy: brcmstb-sata: add missing of_node

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20151117183036.GF8456@google.com>
Date:	Tue, 17 Nov 2015 10:30:36 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	Kishon Vijay Abraham I <kishon@...com>,
	kernel-janitors@...r.kernel.org,
	Gregory Fong <gregory.0xf0@...il.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Andrew Lunn <andrew@...n.ch>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jason Cooper <jason@...edaemon.net>
Subject: Re: [PATCH 1/7] phy: brcmstb-sata: add missing of_node_put

On Tue, Nov 17, 2015 at 06:48:39PM +0100, Julia Lawall wrote:
> On Tue, 17 Nov 2015, Brian Norris wrote:
> > On Tue, Nov 17, 2015 at 07:12:22AM +0100, Julia Lawall wrote:
> > > On Mon, 16 Nov 2015, Brian Norris wrote:
> > > > diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
> > > > index fc48fac003a6..8df29caeeef9 100644
> > > > --- a/drivers/phy/phy-core.c
> > > > +++ b/drivers/phy/phy-core.c
> > > > @@ -697,6 +697,7 @@ struct phy *phy_create(struct device *dev, struct device_node *node,
> > > >  	phy->dev.class = phy_class;
> > > >  	phy->dev.parent = dev;
> > > >  	phy->dev.of_node = node ?: dev->of_node;
> > > > +	of_node_get(phy->dev.of_node);
> > >
> > > Why not put of_node_get around dev->of_node?
> >
> > Like this?
> >
> > 	phy->dev.of_node = node ?: of_node_get(dev->of_node);
> >
> > Or this?
> >
> > 	phy->dev.of_node = of_node_get(node ?: dev->of_node);
> >
> > The former wouldn't do what I proposed; if this PHY device is created
> > with a sub-node of 'dev' rather than dev->of_node, then the caller will
> > pass it in as the 2nd argument to phy_create (i.e., 'node'), and then I
> > expect it's the PHY core's responsibility to refcount it.
> >
> > I'd be fine with the latter. Looks a little better, I suppose.
> 
> I proposed it because I was worried that the of_node field could end up
> containing something that had been freed.  But probably this is not
> possible?

AIUI, the caller of phy_create() should already have a refcount on both
'dev->of_node' and 'node' (if applicable), so nobody should be freeing
it from underneath us right here. But *after* phy_create() returns,
there's no guarantee the caller will hold a reference for us.

So even if it's ever possible, I'd consider it a bug in the caller, not
in phy_create().

> If it is not possible, then the ?: in the function argument is
> probably a bit ugly...

OK, then I'll go with my first proposal.

> Is this something that should be checked for elsewhere?

I expect the same sort of problem shows up plenty of other places. I
don't think many people use CONFIG_OF_DYNAMIC, so the effects of these
failures probably aren't felt by many.

Brian
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/