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

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Date:	Tue, 27 Sep 2011 17:58:59 +0800
From:	Huajun Li <huajun.li.lee@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Huajun Li <huajun.li.lee@...il.com>
Subject: Re: [PATCH 2/2] net: Fix potential memory leak

2011/9/26 Eric Dumazet <eric.dumazet@...il.com>:
> 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 :)
>

To emulate memory allocation fail case, I added code to return
'-ENOMEM' from flow_cache_cpu_prepare(...) even if it could allocate
memory correctly, but did not find panic on my box, maybe the latest
code changed greatly than 2.6.37. :)
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