linux-kernel - Re: [PATCH] devm_memremap_release: fix memremap'd addr handling

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Message-Id: <20160216161843.25aaac7046c7a79e1713c8a2@linux-foundation.org>
Date:	Tue, 16 Feb 2016 16:18:43 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Toshi Kani <toshi.kani@....com>
Cc:	dan.j.williams@...el.com, linux-nvdimm@...1.01.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] devm_memremap_release: fix memremap'd addr handling

On Tue, 16 Feb 2016 09:30:27 -0700 Toshi Kani <toshi.kani@....com> wrote:

> The pmem driver calls devm_memremap() to map a persistent memory
> range.  When the pmem driver is unloaded, this memremap'd range
> is not released.
> 
> Fix devm_memremap_release() to handle a given memremap'd address
> properly.
> 
> ...
>
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -114,7 +114,7 @@ EXPORT_SYMBOL(memunmap);
>  
>  static void devm_memremap_release(struct device *dev, void *res)
>  {
> -	memunmap(res);
> +	memunmap(*(void **)res);
>  }
>  

Huh.  So what happens?  memunmap() decides it isn't a vmalloc address
and we leak a vma?

I'll add a cc:stable to this.