linux-kernel - Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node

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Date:   Wed, 20 Sep 2017 21:39:05 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Rob Herring <robh@...nel.org>, abdul <abdhalee@...ux.vnet.ibm.com>
Cc:     linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Paul Mackerras <paulus@...ba.org>,
        sachinp <sachinp@...ux.vnet.ibm.com>
Subject: Re: [mainline][DLPAR][Oops] OF: ERROR: Bad of_node_put() on /cpus

Rob Herring <robh@...nel.org> writes:

> On Fri, Sep 15, 2017 at 6:04 AM, abdul <abdhalee@...ux.vnet.ibm.com> wrote:
>> Hi,
>>
>> Mainline kernel panics during DLPAR CPU add/remove operation.
>>
>> Machine Type: Power8 PowerVM LPAR
>> kernel 4.13.0
>
> Did 4.12 work or when was it last working? I'm not seeing anything
> recent in the DT code that looks suspicious.

I'm pretty sure it's:

int dlpar_attach_node(struct device_node *dn, struct device_node *parent)
{
	int rc;

	dn->parent = parent;

	rc = of_attach_node(dn);
	if (rc) {
		printk(KERN_ERR "Failed to add device node %pOF\n", dn);
		return rc;
	}

	of_node_put(dn->parent);
HERE    ^^^^^^^^^^

	return 0;
}


Prior to 215ee763f8cb ("powerpc: pseries: remove dlpar_attach_node
dependency on full path"), we re-looked up the parent, and got another
reference on it. That meant the put before the return there was correct.
But now it's not because the caller has a reference to parent but it's
not ours to drop.

Testing a fix, will report back.

cheers