linux-kernel - Re: [PATCH] mm: fix boundary checking in free_bootmem

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Date:	Fri, 21 Mar 2008 21:00:31 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Yinghai Lu <yhlu.kernel@...il.com>, andi@...stfloor.org,
	ak@...e.de, clameter@....com, linux-kernel@...r.kernel.org,
	y-goto@...fujitsu.com, kamezawa.hiroyu@...fujitsu.com
Subject: Re: [PATCH] mm: fix boundary checking in free_bootmem_core


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> diff -puN mm/bootmem.c~mm-fix-boundary-checking-in-free_bootmem_core mm/bootmem.c
> --- a/mm/bootmem.c~mm-fix-boundary-checking-in-free_bootmem_core
> +++ a/mm/bootmem.c
> @@ -125,6 +125,7 @@ static int __init reserve_bootmem_core(b
>  	BUG_ON(!size);
>  	BUG_ON(PFN_DOWN(addr) >= bdata->node_low_pfn);
>  	BUG_ON(PFN_UP(addr + size) > bdata->node_low_pfn);
> +	BUG_ON(addr < bdata->node_boot_start);
>  
>  	sidx = PFN_DOWN(addr - bdata->node_boot_start);
>  	eidx = PFN_UP(addr + size - bdata->node_boot_start);
> @@ -156,21 +157,31 @@ static void __init free_bootmem_core(boo
>  	unsigned long sidx, eidx;
>  	unsigned long i;
>  
> +	BUG_ON(!size);
> +
> +	/* out range */
> +	if (addr + size < bdata->node_boot_start ||
> +		PFN_DOWN(addr) > bdata->node_low_pfn)
> +		return;
>  	/*
>  	 * round down end of usable mem, partially free pages are
>  	 * considered reserved.
>  	 */
> -	BUG_ON(!size);
> -	BUG_ON(PFN_DOWN(addr + size) > bdata->node_low_pfn);
>  
> -	if (addr < bdata->last_success)
> +	if (addr >= bdata->node_boot_start && addr < bdata->last_success)
>  		bdata->last_success = addr;
>  
>  	/*
> -	 * Round up the beginning of the address.
> +	 * Round up to index to the range.
>  	 */
> -	sidx = PFN_UP(addr) - PFN_DOWN(bdata->node_boot_start);
> +	if (PFN_UP(addr) > PFN_DOWN(bdata->node_boot_start))
> +		sidx = PFN_UP(addr) - PFN_DOWN(bdata->node_boot_start);
> +	else
> +		sidx = 0;
> +
>  	eidx = PFN_DOWN(addr + size - bdata->node_boot_start);
> +	if (eidx > bdata->node_low_pfn - PFN_DOWN(bdata->node_boot_start))
> +		eidx = bdata->node_low_pfn - PFN_DOWN(bdata->node_boot_start);
>  
>  	for (i = sidx; i < eidx; i++) {
>  		if (unlikely(!test_and_clear_bit(i, bdata->node_bootmem_map)))
> @@ -421,7 +432,9 @@ int __init reserve_bootmem(unsigned long
>  
>  void __init free_bootmem(unsigned long addr, unsigned long size)
>  {
> -	free_bootmem_core(NODE_DATA(0)->bdata, addr, size);
> +	bootmem_data_t *bdata;
> +	list_for_each_entry(bdata, &bdata_list, list)
> +		free_bootmem_core(bdata, addr, size);
>  }
>  
>  unsigned long __init free_all_bootmem(void)

note, this combination is quite well tested now, on various x86 systems, 
small and large alike, and about a 100 randconfigs booted up.

Acked-by: Ingo Molnar <mingo@...e.hu>
Tested-by: Ingo Molnar <mingo@...e.hu>

	Ingo
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