linux-kernel - Re: [PATCH -next] x86/events:Use struct

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Message-ID: <20220518134920.GA8361@embeddedor>
Date:   Wed, 18 May 2022 08:49:20 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Lin Yujun <linyujun809@...wei.com>
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, tglx@...utronix.de,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, johnny.chenyi@...wei.com,
        chenjiahao16@...wei.com, chenlifu@...wei.com,
        lizhengyu3@...wei.com, liaochang1@...wei.com, wangzhu9@...wei.com,
        xuyihang@...wei.com, chris.zjh@...wei.com, zouyipeng@...wei.com
Subject: Re: [PATCH -next] x86/events:Use struct_size() helper in kzalloc()

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@...wei.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