linux-kernel - Re: [PATCH 3/3] drivers: memory: prohibit offlining of memory blocks with missing sections

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Message-Id: <20151202144556.c21211967d835f5607a909bb@linux-foundation.org>
Date:	Wed, 2 Dec 2015 14:45:56 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Seth Jennings <sjennings@...iantweb.net>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Banman <abanman@....com>, Russ Anderson <rja@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] drivers: memory: prohibit offlining of memory
 blocks with missing sections

On Wed,  2 Dec 2015 09:07:01 -0600 Seth Jennings <sjennings@...iantweb.net> wrote:

> bdee237c and 982792c7 introduced large block sizes for x86.
> This made it possible to have multiple sections per memory
> block where previously, there was a only every one section
> per block.
> 
> Since blocks consist of contiguous ranges of section, there
> can be holes in the blocks where sections are not present.
> If one attempts to offline such a block, a crash occurs since
> the code is not designed to deal with this.
> 
> This patch is a quick fix to gaurd against the crash by
> not allowing blocks with non-present sections to be offlined.
> 
> ...
>
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -303,6 +303,10 @@ static int memory_subsys_offline(struct device *dev)
>  	if (mem->state == MEM_OFFLINE)
>  		return 0;
>  
> +	/* Can't offline block with non-present sections */
> +	if (mem->section_count != sections_per_block)
> +		return -EINVAL;
> +
>  	return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
>  }

[3/3] fixes a kernel crash so I've tagged it for -stable and shall move
it ahead of [1/2] and [2/2], which are merely cleanups.

This assumes that [3/3] is independent of the other two patches.  I'll
eat my hat if it isn't.

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