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Date:   Wed, 18 May 2022 08:49:20 -0500
From:   "Gustavo A. R. Silva" <gustavoars@kernel.org>
To:     Lin Yujun <linyujun809@huawei.com>
Cc:     peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
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        chenjiahao16@huawei.com, chenlifu@huawei.com,
        lizhengyu3@huawei.com, liaochang1@huawei.com, wangzhu9@huawei.com,
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Subject: Re: [PATCH -next] x86/events:Use struct_size() helper in kzalloc()
Message-ID: <20220518134920.GA8361@embeddedor>
References: <20220518131626.109123-1-linyujun809@huawei.com>
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In-Reply-To: <20220518131626.109123-1-linyujun809@huawei.com>
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On Wed, May 18, 2022 at 09:16:26PM +0800, Lin Yujun wrote:
> Replace sizeof() with struct_size() to avoid potential integer
> or heap overflow.

This is not exactly what the patch does.

Your patch is replacing the open-coded calculation of the total amount
of memory to be allocated for rapl_pmus with struct_size().

> 
> Also, address the following sparse warnings:
> arch/x86/events/rapl.c:685:16: warning: using sizeof on a
> flexible structure

This does not address this warning because struct_size()
still make use of sizeof on the struct-with-flex-array,
internally.

So, the mention to the sparse warning should be removed from
this changelog text.

> 
> Signed-off-by: Lin Yujun <linyujun809@huawei.com>
> ---
>  arch/x86/events/rapl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
> index 77e3a47af5ad..c7e79f0ac04f 100644
> --- a/arch/x86/events/rapl.c
> +++ b/arch/x86/events/rapl.c
> @@ -685,7 +685,7 @@ static int __init init_rapl_pmus(void)
>  	int maxdie = topology_max_packages() * topology_max_die_per_package();
>  	size_t size;
>  
> -	size = sizeof(*rapl_pmus) + maxdie * sizeof(struct rapl_pmu *);
> +	size = struct_size(rapl_pmus, pmus, maxdie);
>  	rapl_pmus = kzalloc(size, GFP_KERNEL);

It seems that in this case, size could be entirely replaced by
struct_size().

Thanks
--
Gustavo