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Subject: Re: [PATCH v2 2/2] mm: Add a bounds check in devm_memremap_pages()
To:     Alastair D'Silva <alastair@au1.ibm.com>, alastair@d-silva.org
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Oscar Salvador <osalvador@suse.com>,
        Michal Hocko <mhocko@suse.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        Wei Yang <richard.weiyang@gmail.com>,
        Dan Williams <dan.j.williams@intel.com>, Qian Cai <cai@lca.pw>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Logan Gunthorpe <logang@deltatee.com>,
        Ira Weiny <ira.weiny@intel.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <20190916060544.21824-1-alastair@au1.ibm.com>
 <20190916060544.21824-3-alastair@au1.ibm.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <fa9d30ca-72fe-9ecf-b92c-e651fc117d42@redhat.com>
Date:   Mon, 16 Sep 2019 10:59:06 +0200
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On 16.09.19 08:05, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@d-silva.org>
> 
> The call to check_hotplug_memory_addressable() validates that the memory
> is fully addressable.
> 
> Without this call, it is possible that we may remap pages that is
> not physically addressable, resulting in bogus section numbers
> being returned from __section_nr().
> 
> Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
> ---
>  mm/memremap.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 86432650f829..fd00993caa3e 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -269,6 +269,13 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
>  
>  	mem_hotplug_begin();
>  
> +	error = check_hotplug_memory_addressable(res->start,
> +						 resource_size(res));
> +	if (error) {
> +		mem_hotplug_done();
> +		goto err_checkrange;
> +	}

As I said in reply to v1, please move this out of the memory hotplug
lock. These are static checks.

> +
>  	/*
>  	 * For device private memory we call add_pages() as we only need to
>  	 * allocate and initialize struct page for the device memory. More-
> @@ -324,6 +331,7 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
>  
>   err_add_memory:
>  	kasan_remove_zero_shadow(__va(res->start), resource_size(res));
> + err_checkrange:
>   err_kasan:
>  	untrack_pfn(NULL, PHYS_PFN(res->start), resource_size(res));
>   err_pfn_remap:
> 


-- 

Thanks,

David / dhildenb