netdev - Re: [PATCH net] net/flow: fix fc->percpu NULL pointer dereference

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Message-ID: <CADvbK_dn9QMd8_yRsBMZnjstxjy_L-Pc_UPkyNbyZ=0OORu85A@mail.gmail.com>
Date:   Fri, 9 Jun 2017 16:43:59 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>
Cc:     Hangbin Liu <liuhangbin@...il.com>,
        David Miller <davem@...emloft.net>,
        network dev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] net/flow: fix fc->percpu NULL pointer dereference

On Fri, Jun 9, 2017 at 4:32 PM, Steffen Klassert
<steffen.klassert@...unet.com> wrote:
> On Fri, Jun 09, 2017 at 04:23:01PM +0800, Hangbin Liu wrote:
>> Hi Steffen,
>>
>> BTW, If we put the check in xfrm_policy_flush(), we can prevent it earlier.
>> But If we put the check in flow_cache_percpu_empty(), we can prevent
>> other functions set fc->percpu to NULL, although not much possible : )
>>
>> So I'm not quite sure whether we should put the check in
>> flow_cache_percpu_empty() or in xfrm_policy_flush().
>
> Can't we just call xfrm_policy_fini() first and then flow_cache_fini()?
>
That would be a better fix. seems safe as what flow_cache_fini does
is only to free fcp->hash_table and stop timer, I didn't see  it has
any dependence on xfrm_policy stuff.