[1/9] of: add helper to lookup compatible child node
diff mbox series

Message ID 20180822105547.9634-2-johan@kernel.org
State Superseded
Headers show
Series
  • of: fix compatible-child-node lookups
Related show

Commit Message

Johan Hovold Aug. 22, 2018, 10:55 a.m. UTC
Add of_get_compatible_child() helper that can be used to lookup
compatible child nodes.

Several drivers currently use of_find_compatible_node() to lookup child
nodes while failing to notice that the of_find_ functions search the
entire tree depth-first and therefore can match unrelated (non-child)
nodes. The fact that these functions also drop a reference to the node
they start searching from (e.g. the parent node) is typically also
overlooked, something which can lead to use-after-free bugs.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/of/base.c  | 25 +++++++++++++++++++++++++
 include/linux/of.h |  8 ++++++++
 2 files changed, 33 insertions(+)

Comments

kbuild test robot Aug. 23, 2018, 3:17 a.m. UTC | #1
Hi Johan,

I love your patch! Yet something to improve:

[auto build test ERROR on robh/for-next]
[also build test ERROR on v4.18 next-20180822]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Johan-Hovold/of-fix-compatible-child-node-lookups/20180823-074211
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
config: mips-decstation_defconfig (attached as .config)
compiler: mipsel-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=mips 

All errors (new ones prefixed by >>):

   In file included from include/linux/irqdomain.h:35:0,
                    from arch/mips/include/asm/irq.h:14,
                    from include/linux/irq.h:23,
                    from include/asm-generic/hardirq.h:13,
                    from arch/mips/include/asm/hardirq.h:16,
                    from include/linux/hardirq.h:9,
                    from include/linux/interrupt.h:11,
                    from arch/mips/dec/ecc-berr.c:16:
>> include/linux/of.h:637:28: error: 'of_get_compatible_child' defined but not used [-Werror=unused-function]
    static struct device_node *of_get_compatible_child(const struct device_node *parent,
                               ^~~~~~~~~~~~~~~~~~~~~~~
   cc1: all warnings being treated as errors

vim +/of_get_compatible_child +637 include/linux/of.h

   636	
 > 637	static struct device_node *of_get_compatible_child(const struct device_node *parent,
   638						const char *compatible)
   639	{
   640		return NULL;
   641	}
   642	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Johan Hovold Aug. 23, 2018, 7:39 a.m. UTC | #2
On Thu, Aug 23, 2018 at 11:17:26AM +0800, kbuild test robot wrote:
> Hi Johan,
> 
> I love your patch! Yet something to improve:
> 
> [auto build test ERROR on robh/for-next]
> [also build test ERROR on v4.18 next-20180822]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Johan-Hovold/of-fix-compatible-child-node-lookups/20180823-074211
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
> config: mips-decstation_defconfig (attached as .config)
> compiler: mipsel-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.2.0 make.cross ARCH=mips 
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from include/linux/irqdomain.h:35:0,
>                     from arch/mips/include/asm/irq.h:14,
>                     from include/linux/irq.h:23,
>                     from include/asm-generic/hardirq.h:13,
>                     from arch/mips/include/asm/hardirq.h:16,
>                     from include/linux/hardirq.h:9,
>                     from include/linux/interrupt.h:11,
>                     from arch/mips/dec/ecc-berr.c:16:
> >> include/linux/of.h:637:28: error: 'of_get_compatible_child' defined but not used [-Werror=unused-function]
>     static struct device_node *of_get_compatible_child(const struct device_node *parent,
>                                ^~~~~~~~~~~~~~~~~~~~~~~
>    cc1: all warnings being treated as errors

Bah, I forgot the inline keyword. I'll fix this in a v2, and I can amend
the commit message and mention the start node while at it.

Johan

Patch
diff mbox series

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 466e3c8582f0..bc420d2aa5f5 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -719,6 +719,31 @@  struct device_node *of_get_next_available_child(const struct device_node *node,
 }
 EXPORT_SYMBOL(of_get_next_available_child);
 
+/**
+ * of_get_compatible_child - Find compatible child node
+ * @parent:	parent node
+ * @compatible:	compatible string
+ *
+ * Lookup child node whose compatible property contains the given compatible
+ * string.
+ *
+ * Returns a node pointer with refcount incremented, use of_node_put() on it
+ * when done; or NULL if not found.
+ */
+struct device_node *of_get_compatible_child(const struct device_node *parent,
+				const char *compatible)
+{
+	struct device_node *child;
+
+	for_each_child_of_node(parent, child) {
+		if (of_device_is_compatible(child, compatible))
+			break;
+	}
+
+	return child;
+}
+EXPORT_SYMBOL(of_get_compatible_child);
+
 /**
  *	of_get_child_by_name - Find the child node by name for a given parent
  *	@node:	parent node
diff --git a/include/linux/of.h b/include/linux/of.h
index 4d25e4f952d9..c22982fc1bff 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -290,6 +290,8 @@  extern struct device_node *of_get_next_child(const struct device_node *node,
 extern struct device_node *of_get_next_available_child(
 	const struct device_node *node, struct device_node *prev);
 
+extern struct device_node *of_get_compatible_child(const struct device_node *parent,
+					const char *compatible);
 extern struct device_node *of_get_child_by_name(const struct device_node *node,
 					const char *name);
 
@@ -632,6 +634,12 @@  static inline bool of_have_populated_dt(void)
 	return false;
 }
 
+static struct device_node *of_get_compatible_child(const struct device_node *parent,
+					const char *compatible)
+{
+	return NULL;
+}
+
 static inline struct device_node *of_get_child_by_name(
 					const struct device_node *node,
 					const char *name)