netdev - Re: [PATCH 1/2] ip_gre: fix potential memory leak in erspan

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Date:   Fri, 15 Dec 2017 09:16:59 +0800
From:   严海双 <yanhaishuang@...s.chinamobile.com>
To:     William Tu <u9012063@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        linux-kernel@...r.kernel.org,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH 1/2] ip_gre: fix potential memory leak in erspan_rcv



> On 2017年12月15日, at 上午2:47, William Tu <u9012063@...il.com> wrote:
> 
> On Thu, Dec 14, 2017 at 7:15 AM, Haishuang Yan
> <yanhaishuang@...s.chinamobile.com> wrote:
>> If md is NULL, tun_dst must be freed, otherwise it will cause memory
>> leak.
>> 
>> Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN")
>> Cc: William Tu <u9012063@...il.com>
>> Signed-off-by: Haishuang Yan <yanhaishuang@...s.chinamobile.com>
>> ---
>> net/ipv4/ip_gre.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
>> index d828821..9253d6f 100644
>> --- a/net/ipv4/ip_gre.c
>> +++ b/net/ipv4/ip_gre.c
>> @@ -304,8 +304,10 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi,
>>                                return PACKET_REJECT;
>> 
>>                        md = ip_tunnel_info_opts(&tun_dst->u.tun_info);
>> -                       if (!md)
>> +                       if (!md) {
>> +                               dst_release((struct dst_entry *)tun_dst);
>>                                return PACKET_REJECT;
>> +                       }
> I'm not sure about this. Maybe we don't even need to check "if (!md)"
> since ip_tun_rx_dst does the memory allocation.
> William
> 


Hi, William

I think we need to check “if (!md)”, if md is okay, ip_tunnel_rcv will be responsible to free
tun_dst:

 448 drop:
 449     if (tun_dst)
 450         dst_release((struct dst_entry *)tun_dst);

Thanks.