linux-kernel - Re: [PATCH] mm/vmalloc.c: check the addr first

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Message-ID: <20200928180434.GD458519@iweiny-DESK2.sc.intel.com>
Date:   Mon, 28 Sep 2020 11:04:34 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Hui Su <sh_def@....com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmalloc.c: check the addr first

On Mon, Sep 28, 2020 at 12:33:37AM +0800, Hui Su wrote:
> As the comments said, if @addr is NULL, no operation
> is performed, check the addr first in vfree() and
> vfree_atomic() maybe a better choice.

I don't see how this change helps anything.  kmemleak_free() checks addr so no
danger there.  Also kmemleak_free() contains a pr_debug() which some might find
useful.

Ira

> 
> Signed-off-by: Hui Su <sh_def@....com>
> ---
>  mm/vmalloc.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index be4724b916b3..1cf50749a209 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2305,10 +2305,11 @@ void vfree_atomic(const void *addr)
>  {
>  	BUG_ON(in_nmi());
>  
> -	kmemleak_free(addr);
> -
>  	if (!addr)
>  		return;
> +
> +	kmemleak_free(addr);
> +
>  	__vfree_deferred(addr);
>  }
>  
> @@ -2340,13 +2341,13 @@ void vfree(const void *addr)
>  {
>  	BUG_ON(in_nmi());
>  
> +	if (!addr)
> +		return;
> +
>  	kmemleak_free(addr);
>  
>  	might_sleep_if(!in_interrupt());
>  
> -	if (!addr)
> -		return;
> -
>  	__vfree(addr);
>  }
>  EXPORT_SYMBOL(vfree);
> -- 
> 2.25.1
> 
> 
>