linux-kernel - [PATCH 1/2] clk: Do not register provider with a NULL dev->of

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Date:   Fri, 23 Apr 2021 20:13:33 +0300
From:   Tudor Ambarus <tudor.ambarus@...rochip.com>
To:     <mturquette@...libre.com>, <sboyd@...nel.org>, <nsaenz@...nel.org>,
        <maxime@...no.tech>, <gregkh@...uxfoundation.org>,
        <rafael@...nel.org>, <khilman@...nel.org>,
        <ulf.hansson@...aro.org>, <len.brown@...el.com>, <pavel@....cz>,
        <robh+dt@...nel.org>, <frowand.list@...il.com>, <maz@...nel.org>,
        <tglx@...utronix.de>, <saravanak@...gle.com>,
        <geert@...ux-m68k.org>, <nsaenzjulienne@...e.de>,
        <linux@...ck-us.net>, <guillaume.tucker@...labora.com>
CC:     <linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <corbet@....net>, <nicolas.ferre@...rochip.com>,
        <claudiu.beznea@...rochip.com>, <linux-doc@...r.kernel.org>,
        <linux-pm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-acpi@...r.kernel.org>, <kernel-team@...roid.com>,
        <linux-rpi-kernel@...ts.infradead.org>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: [PATCH 1/2] clk: Do not register provider with a NULL dev->of_node

commit 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
revealed that clk/bcm/clk-raspberrypi.c driver calls
devm_of_clk_add_hw_provider(), with a NULL dev->of_node.

devm_of_clk_add_hw_provider() should not register the provider with
a NULL dev->of_node, as there is no of_node. Apart of the NULL pointer
dereference that will result when calling fwnode_dev_initialized() in
of_clk_add_hw_provider(), another problem is that when two drivers calling
of_clk_add_hw_provider() with np = NULL, their unregistration order is not
guaranteed to be correct. Avoid all the problems and just return -ENODEV
when the callers of devm_of_clk_add_hw_provider() use a NULL dev->of_node,
which seems the natural way to do.

Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Fixes: 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
---
 drivers/clk/clk.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index e2ec1b745243..8b5077cc5e67 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -4634,11 +4634,10 @@ static struct device_node *get_clk_provider_node(struct device *dev)
  * @get: callback for decoding clk_hw
  * @data: context pointer for @get callback
  *
- * Registers clock provider for given device's node. If the device has no DT
- * node or if the device node lacks of clock provider information (#clock-cells)
- * then the parent device's node is scanned for this information. If parent node
- * has the #clock-cells then it is used in registration. Provider is
- * automatically released at device exit.
+ * Registers clock provider for given device's node. If the device node lacks
+ * of clock provider information (#clock-cells) then the parent device's node is
+ * scanned for this information. If parent node has the #clock-cells then it is
+ * used in registration. Provider is automatically released at device exit.
  *
  * Return: 0 on success or an errno on failure.
  */
@@ -4650,6 +4649,9 @@ int devm_of_clk_add_hw_provider(struct device *dev,
 	struct device_node **ptr, *np;
 	int ret;
 
+	if (!dev->of_node)
+		return -ENODEV;
+
 	ptr = devres_alloc(devm_of_clk_release_provider, sizeof(*ptr),
 			   GFP_KERNEL);
 	if (!ptr)
-- 
2.25.1