linux-kernel - Re: [PATCH] usb: ulpi: Add missing of_node_get() in ulpi_of

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Date:   Sat, 11 Nov 2017 16:25:16 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-usb@...r.kernel.org, Rob Clark <robdclark@...il.com>,
        Peter Robinson <pbrobinson@...il.com>
Subject: Re: [PATCH] usb: ulpi: Add missing of_node_get() in
 ulpi_of_register()

On Fri, Nov 10, 2017 at 05:43:00PM -0800, Stephen Boyd wrote:
> In ulpi_of_register() we call of_find_node_by_name() which
> unconditionally calls of_node_put() on the 'from' argument. We
> haven't called of_node_get() though, so we've put the node once
> without getting it first. Add the of_node_get() call so that
> things are properly balanced.
> 
> Fixes: ef6a7bcfb01c ("usb: ulpi: Support device discovery via DT")
> Reported-by: Peter Robinson <pbrobinson@...il.com>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> ---
>  drivers/usb/common/ulpi.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
> index 4aa5195db8ea..59e05eff76f9 100644
> --- a/drivers/usb/common/ulpi.c
> +++ b/drivers/usb/common/ulpi.c
> @@ -182,9 +182,9 @@ static int ulpi_of_register(struct ulpi *ulpi)
>  
>  	/* Find a ulpi bus underneath the parent or the grandparent */
>  	parent = ulpi->dev.parent;
> -	if (parent->of_node)
> +	if (of_node_get(parent->of_node))
>  		np = of_find_node_by_name(parent->of_node, "ulpi");
> -	else if (parent->parent && parent->parent->of_node)
> +	else if (parent->parent && of_node_get(parent->parent->of_node))
>  		np = of_find_node_by_name(parent->parent->of_node, "ulpi");

I'm afraid this isn't the right fix; the code shouldn't have been using
of_find_node_by_name() in the first place as that function searches the
whole device tree depth-first starting at the parent (or grand parent),
which could end up matching an unrelated node.

of_get_child_by_name() is the helper to use for such lookups instead.

Turns out we have a few other driver with similar bugs. I've started
fixing a few of them that'll be sending out per subsystem.

I'll post a fix for this one as follow up to this mail meanwhile.

Thanks,
Johan