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

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Date:   Tue, 23 Oct 2018 11:19:51 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Frank Rowand <frowand.list@...il.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.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 S. Miller" <davem@...emloft.net>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <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

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,
Johan
 
> > Johan Hovold (9):
> >   of: add helper to lookup compatible child node
> >   drm/mediatek: fix OF sibling-node lookup
> >   drm/msm: fix OF child-node lookup
> >   mmc: meson-mx-sdio: fix OF child-node lookup
> >   mtd: nand: atmel: fix OF child-node lookup
> >   net: bcmgenet: fix OF child-node lookup
> >   net: stmmac: dwmac-sun8i: fix OF child-node lookup
> >   NFC: nfcmrvl_uart: fix OF child-node lookup
> >   power: supply: twl4030-charger: fix OF sibling-node lookup
> > 
> >  drivers/gpu/drm/mediatek/mtk_hdmi.c           |  5 ++--
> >  drivers/gpu/drm/msm/adreno/adreno_gpu.c       |  5 ++--
> >  drivers/mmc/host/meson-mx-sdio.c              |  8 ++++--
> >  drivers/mtd/nand/raw/atmel/nand-controller.c  | 11 +++++---
> >  drivers/net/ethernet/broadcom/genet/bcmmii.c  |  2 +-
> >  .../net/ethernet/stmicro/stmmac/dwmac-sun8i.c | 12 +++++++--
> >  drivers/nfc/nfcmrvl/uart.c                    |  5 ++--
> >  drivers/of/base.c                             | 25 +++++++++++++++++++
> >  drivers/power/supply/twl4030_charger.c        |  5 ++--
> >  include/linux/of.h                            |  8 ++++++
> >  10 files changed, 68 insertions(+), 18 deletions(-)