linux-kernel - Re: [PATCH v2] PCI: keystone: fix interrupt-controller-node lookup

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Message-ID: <20171212172537.GB53955@bhelgaas-glaptop.roam.corp.google.com>
Date:   Tue, 12 Dec 2017 11:25:37 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     Johan Hovold <johan@...nel.org>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>,
        Murali Karicheri <m-karicheri2@...com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] PCI: keystone: fix interrupt-controller-node lookup

On Mon, Dec 11, 2017 at 10:42:33AM +0000, Lorenzo Pieralisi wrote:
> On Mon, Dec 11, 2017 at 11:29:55AM +0100, Johan Hovold wrote:
> > On Fri, Nov 17, 2017 at 02:38:31PM +0100, Johan Hovold wrote:
> > > Fix child-node lookup during initialisation which was using the wrong
> > > OF-helper and ended up searching the whole device tree depth-first
> > > starting at the parent rather than just matching on its children.
> > > 
> > > To make things worse, the parent pci node could end up being prematurely
> > > freed as of_find_node_by_name() drops a reference to its first argument.
> > > Any matching child interrupt-controller node was also leaked.
> > > 
> > > Fixes: 0c4ffcfe1fbc ("PCI: keystone: Add TI Keystone PCIe driver")
> > > Cc: stable <stable@...r.kernel.org>     # 3.18
> > > Acked-by: Murali Karicheri <m-karicheri2@...com>
> > > Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> > > Signed-off-by: Johan Hovold <johan@...nel.org>
> > > ---
> > > 
> > > v2
> > >  - amend commit message and mention explicitly that of_find_node_by_name()
> > >    drops a reference to the start node
> > >  - add Murali's and Lorenzo's acks
> > 
> > This one hasn't shown up in linux-next, so sending a reminder to make
> > sure it doesn't fall between the cracks.
> 
> Hi Johan,
> 
> yes it is in the list of fixes to be sent upstream - I was about to
> ask Bjorn to apply it.

Is this something that needs to be merged for v4.15?  If so, I need to
be able to defend it to Linus as being a critical fix.  If the issue
been around for 3 years (v3.18 was tagged Dec 7 2014), that requires
pretty "clear and present danger."

>From the commit log, I see a sub-optimal search (not critical), a
possible use-after-free (could conceivably be critical if people are
tripping over this, but would need more specifics about that), and a
leak (not critical).

Given what I can see now, my inclination would be for Lorenzo to queue
it for v4.16, which would still get in linux-next soonish.

Bjorn