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SubjectRe: [PATCH] netfilter: nf_ct_helper: Fix possible panic when nf_conntrack_helper_unregister is used in an unloadable module
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On 2019/3/1 16:43, Sergei Shtylyov wrote:
> Hello!
>
> On 01.03.2019 8:56, Su Yanjun wrote:
>
>> From: Su Yanjun <suyj.fnst@cn.fujitsu.com>
>>
>> Because nf_conntrack_helper_unregister maybe used in an unloadable
>> module,
>> it uses 'synchronize_rcu' which may cause kernel panic.
>>
>> According to the artical:
>
>    Article?
>
I got it.
>> RCU and Unloadable Modules
>> https://lwn.net/Articles/217484/
>>
>> When we have a heavy rcu callback load, then some of the callbacks
>> might be
>> deferred in order to allow other processing to proceed.
>> sychnorize_rcu does
>> not wait rcu callback complete and module may be unloaded before
>> callback
>> done.
>>
>> This patch uses rcu_barrier instead of synchronize_rcu will prevent this
>                                                         ^ that/which
> missed?
>
Yes.
>> situation.
>>
>> Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
> [...]
>
> MBR, Sergei
>
>
Thanks.

Su




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