linux-kernel - Re: [PATCH] mm/slub: return 0 when object pointer is NULL

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Message-ID: <Yx7dKxwxlNmCr9Ai@hyeyoo>
Date:   Mon, 12 Sep 2022 16:18:03 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Ben Luo <luoben@...ux.alibaba.com>
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org, vbabka@...e.cz,
        roman.gushchin@...ux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/slub: return 0 when object pointer is NULL

On Mon, Sep 12, 2022 at 01:59:39PM +0800, Ben Luo wrote:
> NULL is definitly not a valid address
> 
> Signed-off-by: Ben Luo <luoben@...ux.alibaba.com>
> ---
>  mm/slub.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 862dbd9..50fad18 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -674,7 +674,7 @@ static inline int check_valid_pointer(struct kmem_cache *s,
>  	void *base;
>  
>  	if (!object)
> -		return 1;
> +		return 0;
>  
>  	base = slab_address(slab);
>  	object = kasan_reset_tag(object);
> -- 
> 1.8.3.1
> 

Hello Ben.

The return value is used to check if the @object has valid pointer
in @slab. (used for debugging) the return value is 0 if valid, 1 if invalid.

It does not return a pointer. So changing it to 0 because 1 is invalid
address does not make sense.

-- 
Thanks,
Hyeonggon