linux-kernel - Re: [PATCH v2] md/raid1: Fix stack memory use after return in raid1

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Message-ID: <726fe46d-afd5-4247-86a0-14d7f0eeb3b3@gmail.com>
Date: Thu, 12 Jun 2025 19:46:31 +0800
From: Wang Jinchao <wangjinchao600@...il.com>
To: Yu Kuai <yukuai1@...weicloud.com>, Song Liu <song@...nel.org>
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v2] md/raid1: Fix stack memory use after return in
 raid1_reshape

On 2025/6/12 19:23, Yu Kuai wrote:
> Hi,
> 
> 在 2025/06/12 17:55, Wang Jinchao 写道:
>> Now that we have the same information, I prefer patch-v1 before 
>> refactoring raid1_reshape,
>> because it’s really simple (only one line) and clearer to show the 
>> backup and restore logic.
>> Another reason is that v2 freezes the RAID longer than v1.
>> Would you like me to provide a v3 patch combining the v2 explanation 
>> with the v1 diff?
>> Thanks for your reviewing.
> 
> I don't have preference here, feel free to do this.
> 
> BTW, I feel raid1_reshape can be better coding with following：
> 
> - covert r1bio_pool to use mempool_create_kmalloc_pool(use create
> instead of init to get rid of the werid assigment);
mempool_create_kmalloc_pool also calls init_waitqueue_head(&pool->wait) 
internally, just like mempool_init.
So the issue only exists if newpool is allocated on the stack.
> - no need to reallocate pool_info;
> - convert raid1_info to use krealloc;
I think reallocating pool_info is only for backup and restore, similar 
to newpool.
> 
> Welcome if you are willing to, otherwise I'll find myself sometime.
I'm a newcomer to RAID and can't quite catch up with it right now.
Maybe I can refactor it later, and I look forward to your guidance.
> 
> Thanks,
> Kuai
>