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    Subject[PATCH 3/9] drm/msm: fix OF child-node lookup
    Date
    Use the new of_get_compatible_child() helper to lookup the legacy
    pwrlevels child node instead of using of_find_compatible_node(), which
    searches the entire tree and thus can return an unrelated (i.e.
    non-child) node.

    This also addresses a potential use-after-free (e.g. after probe
    deferral) as the tree-wide helper drops a reference to its first
    argument (i.e. the probed device's node).

    While at it, also fix the related child-node reference leak.

    Fixes: e2af8b6b0ca1 ("drm/msm: gpu: Use OPP tables if we can")
    Cc: stable <stable@vger.kernel.org> # 4.12
    Cc: Jordan Crouse <jcrouse@codeaurora.org>
    Cc: Rob Clark <robdclark@gmail.com>
    Cc: David Airlie <airlied@linux.ie>
    Signed-off-by: Johan Hovold <johan@kernel.org>
    ---
    drivers/gpu/drm/msm/adreno/adreno_gpu.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
    index da1363a0c54d..93d70f4a2154 100644
    --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
    +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
    @@ -633,8 +633,7 @@ static int adreno_get_legacy_pwrlevels(struct device *dev)
    struct device_node *child, *node;
    int ret;

    - node = of_find_compatible_node(dev->of_node, NULL,
    - "qcom,gpu-pwrlevels");
    + node = of_get_compatible_child(dev->of_node, "qcom,gpu-pwrlevels");
    if (!node) {
    dev_err(dev, "Could not find the GPU powerlevels\n");
    return -ENXIO;
    @@ -655,6 +654,8 @@ static int adreno_get_legacy_pwrlevels(struct device *dev)
    dev_pm_opp_add(dev, val, 0);
    }

    + of_node_put(node);
    +
    return 0;
    }

    --
    2.18.0
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