linux-kernel - Re: [PATCH] regulator: of: Add of_node

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Message-ID: <20190726104547.GA4902@sirena.org.uk>
Date:   Fri, 26 Jul 2019 11:45:47 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Nishka Dasgupta <nishkadg.linux@...il.com>
Cc:     lgirdwood@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regulator: of: Add of_node_put() before return in
 function

On Fri, Jul 26, 2019 at 01:02:52PM +0530, Nishka Dasgupta wrote:
> On 24/07/19 9:17 PM, Mark Brown wrote:
> > On Wed, Jul 24, 2019 at 02:02:31PM +0530, Nishka Dasgupta wrote:

> > > The local variable search in regulator_of_get_init_node takes the value
> > > returned by either of_get_child_by_name or of_node_get, both of which
> > > get a node. If this node is not put before returning, it could cause a
> > > memory leak. Hence put search before a mid-loop return statement.
> > > Issue found with Coccinelle.

> > > -		if (!strcmp(desc->of_match, name))
> > > +		if (!strcmp(desc->of_match, name)) {
> > > +			of_node_put(search);
> > >   			return of_node_get(child);
> > > +		}

> > Why not just remove the extra of_node_get() and a comment explaining why
> > it's not needed?

> I'm sorry, I don't think I understand. I'm putting search in this patch; the
> program was already getting child. Should I also return child directly
> instead of getting it again, and continue to put search?

Your new code is dropping a reference then immediately reacquiring one
to return it (introducing a race condition along the way).  Why not just
return the already held reference and not call any functions at all?

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