linux-kernel - Re: [PATCH] ARM: Ignore memory tags with invalid data

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Date:	Tue, 22 Jan 2008 09:18:34 +0000
From:	Ben Dooks <ben@...ff.org>
To:	Corey Minyard <minyard@....org>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>, hvr@....org,
	rmk@....linux.org.uk, nico@....org
Subject: Re: [PATCH] ARM: Ignore memory tags with invalid data

On Mon, Jan 21, 2008 at 10:05:56PM -0600, Corey Minyard wrote:
> From: Corey Minyard <minyard@....org>
> 
> The DNS-323 system has several bogus memory entries in the tag table,
> and it caused the system to crash at startup.  Ignore tag entries that
> are obviously bogus.

This should have gone to the linux-arm-kernel mailing list as well,
so that all the people interested in ARM can see it as soon as
possible. See linux-arm-kernel@...ts.arm.linux.org.uk

The only suggestion I could think of would to be change to having
an check_tag_mem32() function, or put each check on its own line
to make it easier to read what each check is doing.

ie:
	if (meminfo.nr_banks >= NR_BANKS ||
	    tag->u.mem.size & ~PAGE_MASK || /* size is unaligned */
	    tag->u.mem.size == 0 ||	    /* no memory here */
	    tag->u.mem.start & ~PAGE_MASK)  /* start is unaligned */ 
	{

(even without the comments it makes it easier to see what each test
is.
 
> Signed-off-by: Corey Minyard <minyard@....org>
> ---
>  arch/arm/kernel/setup.c |    7 ++++++-
>  1 files changed, 6 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index bf56eb3..dfdb469 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -630,7 +630,12 @@ __tagtable(ATAG_CORE, parse_tag_core);
>  
>  static int __init parse_tag_mem32(const struct tag *tag)
>  {
> -	if (meminfo.nr_banks >= NR_BANKS) {
> +	/*
> +	 * Make sure that the memory size is non-zero, page aligned,
> +	 * and that it doesn't overflow the meminfo table.
> +	 */
> +	if (meminfo.nr_banks >= NR_BANKS || tag->u.mem.size & ~PAGE_MASK ||
> +	    tag->u.mem.size == 0 || tag->u.mem.start & ~PAGE_MASK) {
>  		printk(KERN_WARNING
>  		       "Ignoring memory bank 0x%08x size %dKB\n",
>  			tag->u.mem.start, tag->u.mem.size / 1024);
> --
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-- 
Ben (ben@...ff.org, http://www.fluff.org/)

  'a smiley only costs 4 bytes'
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