linux-kernel - Re: [PATCH v2 0/9] of: fix compatible-child-node lookups

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Date:   Tue, 23 Oct 2018 13:32:56 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        CK Hu <ck.hu@...iatek.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Clark <robdclark@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Josh Wu <rainyfeeling@...look.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Doug Berger <opendmb@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        Giuseppe CAVALLARO <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        joabreu@...opsys.com, Samuel Ortiz <sameo@...ux.intel.com>,
        Sebastian Reichel <sre@...nel.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH v2 0/9] of: fix compatible-child-node lookups

On Tue, Oct 23, 2018 at 4:21 AM Johan Hovold <johan@...nel.org> wrote:
>
> Hi Rob,
>
> On Tue, Sep 04, 2018 at 03:05:57PM +0200, Johan Hovold wrote:
> > Hi all,
> >
> > On Mon, Aug 27, 2018 at 10:21:44AM +0200, Johan Hovold wrote:
> > > Several drivers currently use of_find_compatible_node() to lookup child
> > > nodes while failing to notice that the of_find_ functions search the
> > > entire tree depth-first (from a given start node) and therefore can
> > > match unrelated nodes.
> > >
> > > The fact that these functions also drop a reference to the node they
> > > start searching from (e.g. the parent node) is typically also
> > > overlooked, something which can lead to use-after-free bugs (e.g. after
> > > probe deferrals).
> > >
> > > This series adds a new helper, similar to of_get_child_by_name(),
> > > that can be used to lookup compatible child nodes, and uses the new
> > > helper to fix child-node lookups throughout the tree.
> > >
> > > This is related to the fixes I posted about a year ago, which addressed
> > > a similar anti-pattern when looking up child nodes by name. Since it
> > > took me more than a year to get all those fixes into Linus' tree (one
> > > fix is still pending), and as these fixes depend on the new helper, I'm
> > > suggesting that these all go in through Rob's or Greg's trees.
> > >
> > > Alternatively, the helper could go into to -rc2, and I'll be pinging
> > > submaintainers for the coming year as well. ;)
> >
> > Rob has gotten the helper into -rc2 now:
> >
> >         36156f9241cb of: add helper to lookup compatible child node
> >
> > so feel free to pick these fixes up directly for 4.19-rc or -next,
> > whichever you prefer. I've been able to trigger crashes after probe
> > deferrals due to the use-after-free, but this seems unlikely to be
> > exploitable.
> >
> > I think Rob will be picking up any patches that remain by the end of the
> > release cycle for 4.20.
>
> So far only Ulf has picked up the mmc patch below directly, so if you
> could take the rest through your tree for -rc1 that would be great.

Thanks for the reminder, though before the merge window opened would
have been better. I've applied all but the mtd patch.

Rob