Re: [PATCH -next v2] x86/events:Use struct_size() helper in kzalloc()

[Peter Zijlstra]

On Thu, May 19, 2022 at 10:36:00AM +0800, Lin Yujun wrote:
> Make use of the struct_size() helper instead of an open-coded version,
> in order to avoid any potential type mistakes or integer overflows that,
> in the worst scenario, could lead to heap overflows.
> 
> Signed-off-by: Lin Yujun <linyujun809@xxxxxxxxxx>
> ---
>  arch/x86/events/rapl.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
> index 77e3a47af5ad..8da003e02010 100644
> --- a/arch/x86/events/rapl.c
> +++ b/arch/x86/events/rapl.c
> @@ -683,10 +683,8 @@ static const struct attribute_group *rapl_attr_update[] = {
>  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 *);
> -	rapl_pmus = kzalloc(size, GFP_KERNEL);
> +	rapl_pmus = kzalloc(struct_size(rapl_pmus, pmus, maxdie), GFP_KERNEL);

So I really hate that thing; it's pointless obfuscation. If you're
really worried about the type confusion, write it like:

	size = sizeof(*rapl_pmus) + sizeof(rapl_pmus->pmus[0]) * maxdie;

or something. Otherwise, just go away.