linux-kernel - Re: [PATCH] powerpc: Perform a bounds check in arch_add

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Date:   Tue, 27 Aug 2019 08:28:44 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Alastair D'Silva <alastair@....ibm.com>
Cc:     alastair@...ilva.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@....fr>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: Perform a bounds check in arch_add_memory

On Tue 27-08-19 15:20:46, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@...ilva.org>
> 
> It is possible for firmware to allocate memory ranges outside
> the range of physical memory that we support (MAX_PHYSMEM_BITS).

Doesn't that count as a FW bug? Do you have any evidence of that in the
field? Just wondering...

> This patch adds a bounds check to ensure that any hotplugged
> memory is addressable.
> 
> Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
> ---
>  arch/powerpc/mm/mem.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index 9191a66b3bc5..de18fb73de30 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -111,6 +111,9 @@ int __ref arch_add_memory(int nid, u64 start, u64 size,
>  	unsigned long nr_pages = size >> PAGE_SHIFT;
>  	int rc;
>  
> +	if ((start + size - 1) >> MAX_PHYSMEM_BITS)
> +		return -EINVAL;
> +
>  	resize_hpt_for_hotplug(memblock_phys_mem_size());
>  
>  	start = (unsigned long)__va(start);
> -- 
> 2.21.0

-- 
Michal Hocko
SUSE Labs