linux-kernel - Re: [PATCH] elevator: fix double release for elevator module

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Message-ID: <x49mw1yx54m.fsf@segfault.boston.devel.redhat.com>
Date:	Thu, 23 Apr 2015 10:59:21 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Chao Yu <chao2.yu@...sung.com>
Cc:	axboe@...nel.dk, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] elevator: fix double release for elevator module

Chao Yu <chao2.yu@...sung.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@...sung.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@...hat.com>
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