linux-kernel - [PATCH 3.16 230/346] powerpc/powernv : Drop reference added by kset_find

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Date:   Mon, 14 Nov 2016 00:14:20 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Mukesh Ojha" <mukesh02@...ux.vnet.ibm.com>,
        "Vasant Hegde" <hegdevasant@...ux.vnet.ibm.com>,
        "Benjamin Herrenschmidt" <benh@...nel.crashing.org>
Subject: [PATCH 3.16 230/346] powerpc/powernv : Drop reference added by
 kset_find_obj()

3.16.39-rc1 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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -365,6 +365,7 @@ static int process_dump(void)
 	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)
@@ -376,8 +377,12 @@ static int process_dump(void)
 	 * 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
@@ -246,6 +246,7 @@ static void elog_work_fn(struct work_str
 	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) {
@@ -268,8 +269,12 @@ static void elog_work_fn(struct work_str
 	 * 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;
+	}
 
 	create_elog_obj(log_id, elog_size, elog_type);
 }