linux-kernel - RE: question about drivers/phy/renesas/phy-rcar-gen2.c

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Date:   Tue, 26 Feb 2019 10:01:04 +0100 (CET)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
cc:     Julia Lawall <julia.lawall@...6.fr>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        "Sergei Shtylyov (sergei.shtylyov@...entembedded.com)" 
        <sergei.shtylyov@...entembedded.com>
Subject: RE: question about drivers/phy/renesas/phy-rcar-gen2.c



On Tue, 26 Feb 2019, Yoshihiro Shimoda wrote:

> Hello,
> (Sergei made this code, so I added his email as CC)
>
> I'm sorry for the delayed response.
>
> > From: Julia Lawall, Sent: Sunday, February 3, 2019 4:03 PM
> >
> > Hello,
> >
> > I was wondering whether phy-rcar-gen2.c would use dynamically allocated
> > device nodes?
>
> I'm sorry, but what is "dynamically allocated device nodes"?

Device nodes for which there will be a meor leak if one doesn't put
of_node_put.

julia

>
> Best regards,
> Yoshihiro Shimoda
>
> >  If so, it looks like the following code could cause a
> > use-after-free, due to not incrementing th reference count:
> >
> > 	for_each_child_of_node(dev->of_node, np) {
> > 		struct rcar_gen2_channel *channel = drv->channels + i;
> > 		u32 channel_num;
> > 		int error, n;
> >
> > 		channel->of_node = np;
> > 		...
> > 	}
> >
> > On the other hand, if the reference cound it incrememnted, preventing
> > memory leaks in the case where the probe function fails would entail some
> > complex rewriting of the code, so I thought it would be better to ask
> > first.
> >
> > thanks,
> > julia
>