linux-hardening - Re: [PATCH -next] lockdep: Use memset_startat() helper in reinit

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Date:   Mon, 13 Dec 2021 11:31:44 -0500
From:   Waiman Long <longman@...hat.com>
To:     Xiu Jianfeng <xiujianfeng@...wei.com>, peterz@...radead.org,
        mingo@...hat.com, will@...nel.org, boqun.feng@...il.com
Cc:     wangweiyang2@...wei.com, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org, keescook@...omium.org
Subject: Re: [PATCH -next] lockdep: Use memset_startat() helper in
 reinit_class()

On 12/13/21 08:26, Xiu Jianfeng wrote:
> use memset_startat() helper to simplify the code, there is no functional
> change in this patch.
>
> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>
> ---
>   kernel/locking/lockdep.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 4a882f83aeb9..89b3df51fd98 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -6011,13 +6011,10 @@ static void zap_class(struct pending_free *pf, struct lock_class *class)
>   
>   static void reinit_class(struct lock_class *class)
>   {
> -	void *const p = class;
> -	const unsigned int offset = offsetof(struct lock_class, key);
> -
>   	WARN_ON_ONCE(!class->lock_entry.next);
>   	WARN_ON_ONCE(!list_empty(&class->locks_after));
>   	WARN_ON_ONCE(!list_empty(&class->locks_before));
> -	memset(p + offset, 0, sizeof(*class) - offset);
> +	memset_startat(class, 0, key);
>   	WARN_ON_ONCE(!class->lock_entry.next);
>   	WARN_ON_ONCE(!list_empty(&class->locks_after));
>   	WARN_ON_ONCE(!list_empty(&class->locks_before));

LGTM

Acked-by: Waiman Long <longman@...hat.com>