[PATCH] powerpc/powernv : Drop reference added by kset_find_obj()

[PATCH] powerpc/powernv : Drop reference added by kset_find_obj()

[Mukesh Ojha]

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@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
---
 arch/powerpc/platforms/powernv/opal-dump.c | 7 ++++++-
 arch/powerpc/platforms/powernv/opal-elog.c | 7 ++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal-dump.c b/arch/powerpc/platforms/powernv/opal-dump.c
index 2ee9643..4c82782 100644
--- 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, void *data)
 	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, void *data)
 	 * 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)
diff --git a/arch/powerpc/platforms/powernv/opal-elog.c b/arch/powerpc/platforms/powernv/opal-elog.c
index 37f959b..f2344cb 100644
--- 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, void *data)
 	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, void *data)
 	 * 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);
 
-- 
2.7.4

Re: [PATCH] powerpc/powernv : Drop reference added by kset_find_obj()

[Vasant Hegde]

On 08/22/2016 12:17 PM, Mukesh Ojha wrote:
> 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@linux.vnet.ibm.com>


I've reviewed and tested this patch. Looks good to me.

Reviewed-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>

-Vasant


> Cc: stable@vger.kernel.org
> ---
>   arch/powerpc/platforms/powernv/opal-dump.c | 7 ++++++-
>   arch/powerpc/platforms/powernv/opal-elog.c | 7 ++++++-
>   2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/opal-dump.c b/arch/powerpc/platforms/powernv/opal-dump.c
> index 2ee9643..4c82782 100644
> --- 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, void *data)
>   	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, void *data)
>   	 * 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)
> diff --git a/arch/powerpc/platforms/powernv/opal-elog.c b/arch/powerpc/platforms/powernv/opal-elog.c
> index 37f959b..f2344cb 100644
> --- 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, void *data)
>   	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, void *data)
>   	 * 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);
>