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Subject: Re: [PATCH v2 1/4] md/raid10: fix null-ptr-deref of mreplace in
 raid10_sync_request
To:     Song Liu <song@kernel.org>, linan666@huaweicloud.com
Cc:     bingjingc@synology.com, allenpeng@synology.com,
        alexwu@synology.com, shli@fb.com, neilb@suse.de,
        linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
        linan122@huawei.com, yi.zhang@huawei.com, houtao1@huawei.com,
        yangerkun@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
References: <20230526074551.669792-1-linan666@huaweicloud.com>
 <20230526074551.669792-2-linan666@huaweicloud.com>
 <CAPhsuW5ThXyAL2rAyWZC31etY27fqsG+eFHcHtzfCS9Da4bosw@mail.gmail.com>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <5d836b41-2dff-e829-2e18-97ea4565b5bc@huaweicloud.com>
Date:   Sat, 27 May 2023 09:17:45 +0800
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Hi,

在 2023/05/27 5:38, Song Liu 写道:
> On Fri, May 26, 2023 at 12:47 AM <linan666@huaweicloud.com> wrote:                    }
> 
> To make sure I understand the issue correctly:
> 
> The null-ptr-deref only happens when the Faulty bit was set after the
> last check and before this check below, right?

Yes, you're right.

Thanks,
Kuai
> 
>> -                       if (mreplace && test_bit(Faulty, &mreplace->flags))
>> -                               mreplace = NULL;
>>                          /* Unless we are doing a full sync, or a replacement
>>                           * we only need to recover the block if it is set in
>>                           * the bitmap
> 
> Thanks,
> Song
>