linux-kernel - Re: [PATCH] powerpc/mm: fix a hardcode on memory boundary checking

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Date:   Tue, 31 Jan 2017 20:11:41 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Rui Teng <rui.teng@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        jia he <hejianet@...ux.vnet.ibm.com>,
        Rui Teng <rui.teng@...ux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc/mm: fix a hardcode on memory boundary checking

Rui Teng <rui.teng@...ux.vnet.ibm.com> writes:

> The offset of hugepage block will not be 16G, if the expected
> page is more than one. Calculate the totol size instead of the
> hardcode value.

I assume you found this by code inspection and not by triggering an
actual bug?

cheers

> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 8033493..b829f8e 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -506,7 +506,7 @@ static int __init htab_dt_scan_hugepage_blocks(unsigned long node,
>  	printk(KERN_INFO "Huge page(16GB) memory: "
>  			"addr = 0x%lX size = 0x%lX pages = %d\n",
>  			phys_addr, block_size, expected_pages);
> -	if (phys_addr + (16 * GB) <= memblock_end_of_DRAM()) {
> +	if (phys_addr + block_size * expected_pages <= memblock_end_of_DRAM()) {
>  		memblock_reserve(phys_addr, block_size * expected_pages);
>  		add_gpage(phys_addr, block_size, expected_pages);
>  	}
> -- 
> 2.9.0