linux-kernel - [PATCH 4.7 037/184] powerpc/powernv : Drop reference added by kset_find

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Message-Id: <20160922174050.297154415@linuxfoundation.org>
Date:   Thu, 22 Sep 2016 19:39:31 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mukesh Ojha <mukesh02@...ux.vnet.ibm.com>,
        Vasant Hegde <hegdevasant@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: [PATCH 4.7 037/184] powerpc/powernv : Drop reference added by kset_find_obj()

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mukesh Ojha <mukesh02@...ux.vnet.ibm.com>

commit a9cbf0b2195b695cbeeeecaa4e2770948c212e9a upstream.

In a situation, where Linux kernel gets notified about duplicate error log
from OPAL, it is been observed that kernel fails to remove sysfs entries
(/sys/firmware/opal/elog/0xXXXXXXXX) of such error logs. This is because,
we currently search the error log/dump kobject in the kset list via
'kset_find_obj()' routine. Which eventually increment the reference count
by one, once it founds the kobject.

So, unless we decrement the reference count by one after it found the kobject,
we would not be able to release the kobject properly later.

This patch adds the 'kobject_put()' which was missing earlier.

Signed-off-by: Mukesh Ojha <mukesh02@...ux.vnet.ibm.com>
Reviewed-by: Vasant Hegde <hegdevasant@...ux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/platforms/powernv/opal-dump.c |    7 ++++++-
 arch/powerpc/platforms/powernv/opal-elog.c |    7 ++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

--- a/arch/powerpc/platforms/powernv/opal-dump.c
+++ b/arch/powerpc/platforms/powernv/opal-dump.c
@@ -370,6 +370,7 @@ static irqreturn_t process_dump(int irq,
 	uint32_t dump_id, dump_size, dump_type;
 	struct dump_obj *dump;
 	char name[22];
+	struct kobject *kobj;
 
 	rc = dump_read_info(&dump_id, &dump_size, &dump_type);
 	if (rc != OPAL_SUCCESS)
@@ -381,8 +382,12 @@ static irqreturn_t process_dump(int irq,
 	 * that gracefully and not create two conflicting
 	 * entries.
 	 */
-	if (kset_find_obj(dump_kset, name))
+	kobj = kset_find_obj(dump_kset, name);
+	if (kobj) {
+		/* Drop reference added by kset_find_obj() */
+		kobject_put(kobj);
 		return 0;
+	}
 
 	dump = create_dump_obj(dump_id, dump_size, dump_type);
 	if (!dump)
--- a/arch/powerpc/platforms/powernv/opal-elog.c
+++ b/arch/powerpc/platforms/powernv/opal-elog.c
@@ -247,6 +247,7 @@ static irqreturn_t elog_event(int irq, v
 	uint64_t elog_type;
 	int rc;
 	char name[2+16+1];
+	struct kobject *kobj;
 
 	rc = opal_get_elog_size(&id, &size, &type);
 	if (rc != OPAL_SUCCESS) {
@@ -269,8 +270,12 @@ static irqreturn_t elog_event(int irq, v
 	 * that gracefully and not create two conflicting
 	 * entries.
 	 */
-	if (kset_find_obj(elog_kset, name))
+	kobj = kset_find_obj(elog_kset, name);
+	if (kobj) {
+		/* Drop reference added by kset_find_obj() */
+		kobject_put(kobj);
 		return IRQ_HANDLED;
+	}
 
 	create_elog_obj(log_id, elog_size, elog_type);