linux-kernel - [PATCH v2] clk: Skip clk provider registration when np is NULL

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Date:   Mon, 26 Apr 2021 09:56:18 +0300
From:   Tudor Ambarus <tudor.ambarus@...rochip.com>
To:     <gregkh@...uxfoundation.org>, <rafael@...nel.org>,
        <mturquette@...libre.com>, <sboyd@...nel.org>, <nsaenz@...nel.org>,
        <maxime@...no.tech>, <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 v2] clk: Skip clk provider registration when np is NULL

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, which resulted in a
NULL pointer dereference in of_clk_add_hw_provider() when calling
fwnode_dev_initialized().

Returning 0 is reducing the if conditions in driver code and is being
consistent with the CONFIG_OF=n inline stub that returns 0 when CONFIG_OF
is disabled. The downside is that drivers will maybe register clkdev lookups
when they don't need to and waste some memory.

Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Fixes: 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
Fixes: 3c9ea42802a1 ("clk: Mark fwnodes when their clock provider is added/removed")
Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
Reviewed-by: Stephen Boyd <sboyd@...nel.org>
---
v2:
- s/return 0;/return; in void of_clk_del_provider()
- add second fixes tag and Stephen's R-b tag
The opinions on whether to return an error or zero were split. Returning 0
and skipping the logic was considered safer as we don't know for sure if
other drivers are affected. See:
https://lore.kernel.org/lkml/d24bebc5-0f78-021f-293f-e58defa32531@samsung.com/
https://lore.kernel.org/lkml/20210423171335.262316-1-tudor.ambarus@microchip.com/

 drivers/clk/clk.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index a3b30f7de2ef..b47460b40d14 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -4552,6 +4552,9 @@ int of_clk_add_provider(struct device_node *np,
 	struct of_clk_provider *cp;
 	int ret;
 
+	if (!np)
+		return 0;
+
 	cp = kzalloc(sizeof(*cp), GFP_KERNEL);
 	if (!cp)
 		return -ENOMEM;
@@ -4591,6 +4594,9 @@ int of_clk_add_hw_provider(struct device_node *np,
 	struct of_clk_provider *cp;
 	int ret;
 
+	if (!np)
+		return 0;
+
 	cp = kzalloc(sizeof(*cp), GFP_KERNEL);
 	if (!cp)
 		return -ENOMEM;
@@ -4688,6 +4694,9 @@ void of_clk_del_provider(struct device_node *np)
 {
 	struct of_clk_provider *cp;
 
+	if (!np)
+		return;
+
 	mutex_lock(&of_clk_mutex);
 	list_for_each_entry(cp, &of_clk_providers, link) {
 		if (cp->node == np) {
-- 
2.25.1