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

[Johan Hovold]

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.

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(-)