[PATCH] elevator: fix double release for elevator module

[PATCH] elevator: fix double release for elevator module

[Chao Yu]

Our issue is descripted in below call path:
->elevator_init
 ->elevator_init_fn
  ->{cfq,deadline,noop}_init_queue
   ->elevator_alloc
    ->kzalloc_node
   fail to call kzalloc_node and then put module in elevator_alloc;
fail to call elevator_init_fn and then put module again in elevator_init.

Remove elevator_put invoking in error path of elevator_alloc to avoid
double release issue.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
---
 block/elevator.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/block/elevator.c b/block/elevator.c
index d146a5e..8985038 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -157,7 +157,7 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
 
 	eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
 	if (unlikely(!eq))
-		goto err;
+		return NULL;
 
 	eq->type = e;
 	kobject_init(&eq->kobj, &elv_ktype);
@@ -165,9 +165,6 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
 	hash_init(eq->hash);
 
 	return eq;
-err:
-	elevator_put(e);
-	return NULL;
 }
 EXPORT_SYMBOL(elevator_alloc);
 
-- 
2.3.3

Re: [PATCH] elevator: fix double release for elevator module

[Jeff Moyer]

Chao Yu <chao2.yu@samsung.com> writes:

> Our issue is descripted in below call path:
> ->elevator_init
>  ->elevator_init_fn
>   ->{cfq,deadline,noop}_init_queue
>    ->elevator_alloc
>     ->kzalloc_node
>    fail to call kzalloc_node and then put module in elevator_alloc;
> fail to call elevator_init_fn and then put module again in elevator_init.
>
> Remove elevator_put invoking in error path of elevator_alloc to avoid
> double release issue.
>
> Signed-off-by: Chao Yu <chao2.yu@samsung.com>
> ---
>  block/elevator.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/block/elevator.c b/block/elevator.c
> index d146a5e..8985038 100644
> --- a/block/elevator.c
> +++ b/block/elevator.c
> @@ -157,7 +157,7 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
>  
>  	eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
>  	if (unlikely(!eq))
> -		goto err;
> +		return NULL;
>  
>  	eq->type = e;
>  	kobject_init(&eq->kobj, &elv_ktype);
> @@ -165,9 +165,6 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
>  	hash_init(eq->hash);
>  
>  	return eq;
> -err:
> -	elevator_put(e);
> -	return NULL;
>  }
>  EXPORT_SYMBOL(elevator_alloc);

You could have posted the two patches together, as they are related.
Anyway, looks good to me.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>

Re: [PATCH] elevator: fix double release for elevator module

[Jens Axboe]

On 04/23/2015 08:59 AM, Jeff Moyer wrote:
> Chao Yu <chao2.yu@samsung.com> writes:
>
>> Our issue is descripted in below call path:
>> ->elevator_init
>>   ->elevator_init_fn
>>    ->{cfq,deadline,noop}_init_queue
>>     ->elevator_alloc
>>      ->kzalloc_node
>>     fail to call kzalloc_node and then put module in elevator_alloc;
>> fail to call elevator_init_fn and then put module again in elevator_init.
>>
>> Remove elevator_put invoking in error path of elevator_alloc to avoid
>> double release issue.
>>
>> Signed-off-by: Chao Yu <chao2.yu@samsung.com>
>> ---
>>   block/elevator.c | 5 +----
>>   1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/block/elevator.c b/block/elevator.c
>> index d146a5e..8985038 100644
>> --- a/block/elevator.c
>> +++ b/block/elevator.c
>> @@ -157,7 +157,7 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
>>
>>   	eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
>>   	if (unlikely(!eq))
>> -		goto err;
>> +		return NULL;
>>
>>   	eq->type = e;
>>   	kobject_init(&eq->kobj, &elv_ktype);
>> @@ -165,9 +165,6 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
>>   	hash_init(eq->hash);
>>
>>   	return eq;
>> -err:
>> -	elevator_put(e);
>> -	return NULL;
>>   }
>>   EXPORT_SYMBOL(elevator_alloc);
>
> You could have posted the two patches together, as they are related.
> Anyway, looks good to me.
>
> Reviewed-by: Jeff Moyer <jmoyer@redhat.com>

Agree, it should be one patch. I've combined them, and applied the fix 
for 4.1. Thanks.

-- 
Jens Axboe

RE: [PATCH] elevator: fix double release for elevator module

[Chao Yu]

Hi Jens and Jeff,

Thanks for your review and help! :)

Regards,

> -----Original Message-----
> From: Jens Axboe [mailto:axboe@kernel.dk]
> Sent: Friday, April 24, 2015 12:49 AM
> To: Jeff Moyer; Chao Yu
> Cc: linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] elevator: fix double release for elevator module
> 
> On 04/23/2015 08:59 AM, Jeff Moyer wrote:
> > Chao Yu <chao2.yu@samsung.com> writes:
> >
> >> Our issue is descripted in below call path:
> >> ->elevator_init
> >>   ->elevator_init_fn
> >>    ->{cfq,deadline,noop}_init_queue
> >>     ->elevator_alloc
> >>      ->kzalloc_node
> >>     fail to call kzalloc_node and then put module in elevator_alloc;
> >> fail to call elevator_init_fn and then put module again in elevator_init.
> >>
> >> Remove elevator_put invoking in error path of elevator_alloc to avoid
> >> double release issue.
> >>
> >> Signed-off-by: Chao Yu <chao2.yu@samsung.com>
> >> ---
> >>   block/elevator.c | 5 +----
> >>   1 file changed, 1 insertion(+), 4 deletions(-)
> >>
> >> diff --git a/block/elevator.c b/block/elevator.c
> >> index d146a5e..8985038 100644
> >> --- a/block/elevator.c
> >> +++ b/block/elevator.c
> >> @@ -157,7 +157,7 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
> >>
> >>   	eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
> >>   	if (unlikely(!eq))
> >> -		goto err;
> >> +		return NULL;
> >>
> >>   	eq->type = e;
> >>   	kobject_init(&eq->kobj, &elv_ktype);
> >> @@ -165,9 +165,6 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
> >>   	hash_init(eq->hash);
> >>
> >>   	return eq;
> >> -err:
> >> -	elevator_put(e);
> >> -	return NULL;
> >>   }
> >>   EXPORT_SYMBOL(elevator_alloc);
> >
> > You could have posted the two patches together, as they are related.
> > Anyway, looks good to me.
> >
> > Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
> 
> Agree, it should be one patch. I've combined them, and applied the fix
> for 4.1. Thanks.
> 
> --
> Jens Axboe