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

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Date:   Tue, 26 Feb 2019 08:54:21 +0000
From:   Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
To:     Julia Lawall <julia.lawall@...6.fr>
CC:     "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

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"?

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