linux-kernel - Re: [PATCH v4] memory_hotplug: Add a bounds check to __add

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Date:   Thu, 26 Sep 2019 09:40:05 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     Alastair D'Silva <alastair@....ibm.com>
Cc:     alastair@...ilva.org, Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        David Hildenbrand <david@...hat.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Dan Williams <dan.j.williams@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] memory_hotplug: Add a bounds check to __add_pages

On Thu, Sep 26, 2019 at 11:34:05AM +1000, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@...ilva.org>
> @@ -291,6 +307,10 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
>  	unsigned long nr, start_sec, end_sec;
>  	struct vmem_altmap *altmap = restrictions->altmap;
>  
> +	err = check_hotplug_memory_addressable(pfn, nr_pages);
> +	if (err)
> +		return err;
> +

I am probably off here because 1) I am jumping blind in a middle of a discussion and
2) I got back from holydays yesterday, so bear with me.

Would not be better to just place the check in add_memory_resource instead?
Take into account that we create the memory mapping for this range in
arch_add_memory, so it looks weird to me to create the mapping if we are going to
fail right after because the range is simply off.

But as I said, I might be missing some previous discussion. 

-- 
Oscar Salvador
SUSE L3