linux-kernel - Re: [PATCH 1/1] z3fold: fix memory leak

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Date:   Wed, 4 Apr 2018 15:20:39 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Xidong Wang <wangxidong_97@....com>
Cc:     Vitaly Wool <vitalywool@...il.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] z3fold: fix memory leak

On Wed,  4 Apr 2018 08:51:51 +0800 Xidong Wang <wangxidong_97@....com> wrote:

> In function z3fold_create_pool(), the memory allocated by
> __alloc_percpu() is not released on the error path that pool->compact_wq
> , which holds the return value of create_singlethread_workqueue(), is NULL.
> This will result in a memory leak bug.
>
> ...
>
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -490,6 +490,7 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
>  out_wq:
>  	destroy_workqueue(pool->compact_wq);
>  out:
> +	free_percpu(pool->unbuddied);
>  	kfree(pool);
>  	return NULL;
>  }

That isn't right.  If the initial kzallc fails we'll goto out with
pool==NULL.

Please check:

--- a/mm/z3fold.c~z3fold-fix-memory-leak-fix
+++ a/mm/z3fold.c
@@ -479,7 +479,7 @@ static struct z3fold_pool *z3fold_create
 	pool->name = name;
 	pool->compact_wq = create_singlethread_workqueue(pool->name);
 	if (!pool->compact_wq)
-		goto out;
+		goto out_unbuddied;
 	pool->release_wq = create_singlethread_workqueue(pool->name);
 	if (!pool->release_wq)
 		goto out_wq;
@@ -489,9 +489,10 @@ static struct z3fold_pool *z3fold_create
 
 out_wq:
 	destroy_workqueue(pool->compact_wq);
-out:
+out_unbuddied:
 	free_percpu(pool->unbuddied);
 	kfree(pool);
+out:
 	return NULL;
 }
 
_