linux-kernel - Re: [PATCH] once: Fix panic when module unload

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Message-ID: <09551b30-f73a-f248-5030-5c57c8457547@huawei.com>
Date:   Wed, 4 Aug 2021 09:49:51 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Hannes Frederic Sowa <hannes@...essinduktion.org>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>
CC:     Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Minmin chen <chenmingmin@...wei.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] once: Fix panic when module unload


On 2021/8/3 17:59, Hannes Frederic Sowa wrote:
> Hello,
>
> On Tue, Aug 3, 2021, at 04:11, Kefeng Wang wrote:
>> Hi ALL, I don't know who maintain the lib/once.c, add Greg and Andrew too,
>>
>> Hi David, I check the history, the lib/once.c is from net/core/utils.c
>> since
>>
>> commit 46234253b9363894a254844a6550b4cc5f3edfe8
>> Author: Hannes Frederic Sowa <hannes@...essinduktion.org>
>> Date:   Thu Oct 8 01:20:35 2015 +0200
>>
>>       net: move net_get_random_once to lib
>>
>> This bug is found in our product test, we want to make sure that whether
>> this solution
>>
>> is correct or not, so could David or any others help to review this patch.
>>
>> Many thinks.
> Thanks for the patch.
>
> I see that it got marked as not applicable for the net trees:
> <https://patchwork.kernel.org/project/netdevbpf/patch/20210622022138.23048-1-wangkefeng.wang@huawei.com/>
>
> Back then I added this code via the net/ tree thus I think it should get
> picked up nonetheless hopefully.
>
> Regarding your patch, I think it mostly looks fine:
>
> It might be worthwhile to increment the reference counter inside the
> preempt disabled bracket in find_module_by_key (and thus also rename
> that function to make this fact more clear).
>
> The other option would be to use the macro DO_ONCE and always pass in
> THIS_MODULE from there, increment its ref counter in once_disable_jump.
> This might be more canonical.

Thanks for your replay.

Yes, that was my first thought, add THIS_MODULE to __do_once_done(),

I will change to this way to fix the issue.


>
> Thanks and sorry for the delay,
> Hannes
> .
>