Re: [PATCH] spmi: hisi-spmi-controller: manage the OF node reference in device initialization and cleanup

[Joe Hattori]

Thank you for your review.

On 12/17/24 19:55, Krzysztof Kozlowski wrote:
> On 17/12/2024 05:26, Joe Hattori wrote:
> > spmi_controller_probe() increments the refcount of an OF node, but does
> > not release it. Instead, call of_node_get() in spmi_controller_alloc()
> > and release it in spmi_ctrl_release() to avoid the reference leak.
> >
> > This bug was found by an experimental static analysis tool that I am
> > developing.
> >
> > Fixes: e562cf3aea3e ("spmi: hisi-spmi-controller: move driver from staging")
> > Signed-off-by: Joe Hattori <joe@xxxxxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/spmi/hisi-spmi-controller.c | 1 -
> >   drivers/spmi/spmi.c                 | 3 ++-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/spmi/hisi-spmi-controller.c b/drivers/spmi/hisi-spmi-controller.c
> > index 3cafdf22c909..dd21c5d1ca83 100644
> > --- a/drivers/spmi/hisi-spmi-controller.c
> > +++ b/drivers/spmi/hisi-spmi-controller.c
> > @@ -301,7 +301,6 @@ static int spmi_controller_probe(struct platform_device *pdev)
> >   	spin_lock_init(&spmi_controller->lock);
> >   
> >   	ctrl->dev.parent = pdev->dev.parent;
> > -	ctrl->dev.of_node = of_node_get(pdev->dev.of_node);
> >   
> >   	/* Callbacks */
> >   	ctrl->read_cmd = spmi_read_cmd;
> > diff --git a/drivers/spmi/spmi.c b/drivers/spmi/spmi.c
> > index fb0101da1485..e662a7a78df2 100644
> > --- a/drivers/spmi/spmi.c
> > +++ b/drivers/spmi/spmi.c
> > @@ -36,6 +36,7 @@ static void spmi_ctrl_release(struct device *dev)
> >   	struct spmi_controller *ctrl = to_spmi_controller(dev);
> >   
> >   	ida_free(&ctrl_ida, ctrl->nr);
> > +	of_node_put(dev->of_node);
>
>
> Aren't other drivers like PMIC arbiter overwriting this with different
> value, thus basically you are dropping reference which was not obtained
> and causing actual use-after-free?

Should have caught this one. It is actually storing the same OF node 
pointer so it doesn't cause UAF, but is very confusing anyway. Addressed 
in the v2 patch.

> Best regards,
> Krzysztof

Best,
Joe