netdev - Re: [PATCH 2/2] net: Fix potential memory leak

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Date:	Mon, 26 Sep 2011 08:09:13 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Huajun Li <huajun.li.lee@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/2] net: Fix potential memory leak

Le samedi 24 septembre 2011 à 23:57 +0800, Huajun Li a écrit :
> While preparing flow caches, once fail may cause potential memory leak , fix it.
> 
> Signed-off-by: Huajun Li <huajun.li.lee@...il.com>
> ---
>  net/core/flow.c |   19 ++++++++++++++++++-
>  1 files changed, 18 insertions(+), 1 deletions(-)
> 
> diff --git a/net/core/flow.c b/net/core/flow.c
> index ba3e617..2dcaa03 100644
> --- a/net/core/flow.c
> +++ b/net/core/flow.c
> @@ -420,7 +420,7 @@ static int __init flow_cache_init(struct flow_cache *fc)
> 
>  	for_each_online_cpu(i) {
>  		if (flow_cache_cpu_prepare(fc, i))
> -			return -ENOMEM;
> +			goto err;
>  	}
>  	fc->hotcpu_notifier = (struct notifier_block){
>  		.notifier_call = flow_cache_cpu,
> @@ -433,6 +433,23 @@ static int __init flow_cache_init(struct flow_cache *fc)
>  	add_timer(&fc->rnd_timer);
> 
>  	return 0;
> +err:
> +	if (fc->percpu) {
> +		free_percpu(fc->percpu);
> +		fc->percpu = NULL;
> +	}
> +
> +	/*
> +	 * Check each possible CPUs rather than online ones because they may be
> +	 * offline before the notifier is registered.
> +	 */

Please remove this comment.


> +	for_each_possible_cpu(i) {
> +		struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, i);
> +		kfree(fcp->hash_table);
> +		fcp->hash_table = NULL;
> +	}

You access fc->percpu after freeing it...

> +
> +	return -ENOMEM;
>  }
> 
>  static int __init flow_cache_init_global(void)

Previous to 2.6.37 (commit 83b6b1f5d134), a memory allocation at this
stage was panicing the box, so no worry about mem leak :)

Now I wonder if a proper patch would not print a nice message in
flow_cache_init_global() if flow_cache_init() returns an error, instead
of silently panicing or something worse...

Before submitting a new patch, could you test this case (injecting a
memalloc error in flow_cache_cpu_prepare() for example.



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