linux-kernel - [PATCH 1/3] ARM: hisi: fix error handling and missing of_node

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Date:   Sat, 13 Apr 2019 09:14:15 +0200
From:   Nicholas Mc Guire <hofrat@...dl.org>
To:     Russell King <linux@...linux.org.uk>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Tony Lindgren <tony@...mide.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Janusz Krzysztofik <jmkrzyszt@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Nicholas Mc Guire <hofrat@...dl.org>
Subject: [PATCH 1/3] ARM: hisi: fix error handling and missing of_node_put

of_iomap() can return NULL which seems critical here and thus should be
explicitly flagged so that the cause of system halting can be understood.
As of_find_compatible_node() is returning a device node with refcount
incremented it must be explicitly decremented here.

Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
Fixes: commit 7fda91e73155 ("ARM: hisi: enable smp for HiP01")
---

Problem located by experimental coccinelle script

Patch was compile tested with: hisi_defconfig (implies CONFIG_SMP=y)

There are two change related checkpatch warnings about
"WARNING: Avoid crashing the kernel - try using WARN_ON"
but here the BUG_ON() seems adequate.

Patch is against 4.18-rc3 (localversion-next is next-20180712)

 arch/arm/mach-hisi/hotplug.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/mach-hisi/hotplug.c b/arch/arm/mach-hisi/hotplug.c
index a129aae..3b0d1c6 100644
--- a/arch/arm/mach-hisi/hotplug.c
+++ b/arch/arm/mach-hisi/hotplug.c
@@ -219,10 +219,10 @@ void hip01_set_cpu(int cpu, bool enable)
 
 	if (!ctrl_base) {
 		np = of_find_compatible_node(NULL, NULL, "hisilicon,hip01-sysctrl");
-		if (np)
-			ctrl_base = of_iomap(np, 0);
-		else
-			BUG();
+		BUG_ON(!np);
+		ctrl_base = of_iomap(np, 0);
+		of_node_put(np);
+		BUG_ON(!ctrl_base);
 	}
 
 	if (enable) {
-- 
2.1.4