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Date:   Mon, 10 Apr 2023 20:29:35 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Peng Zhang <zhangpeng.00@bytedance.com>
Cc:     Liam.Howlett@oracle.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, maple-tree@lists.infradead.org,
        David Binderman <dcb314@hotmail.com>, stable@vger.kernel.org
Subject: Re: [PATCH v2] maple_tree: Use correct variable type in sizeof
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In-Reply-To: <20230411023513.15227-1-zhangpeng.00@bytedance.com>
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On Tue, 11 Apr 2023 10:35:13 +0800 Peng Zhang <zhangpeng.00@bytedance.com> wrote:

> The type of variable pointed to by pivs is unsigned long, but the type
> used in sizeof is a pointer type. Change it to unsigned long.

Thanks, but there's nothing in this changelog which explains why a
-stable backport is being proposed.  When fixing a bug, please always
describe the user-visible effects of that bug.

> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -3255,7 +3255,7 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
>  
>  		if (tmp < max_p)
>  			memset(pivs + tmp, 0,
> -			       sizeof(unsigned long *) * (max_p - tmp));
> +			       sizeof(unsigned long) * (max_p - tmp));
>  
>  		if (tmp < mt_slots[mt])
>  			memset(slots + tmp, 0, sizeof(void *) * (max_s - tmp));

Is there any situation in which
sizeof(unsigned long *) != sizeof(unsigned long)?