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

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Message-ID: <46af0847-24f4-a657-977e-a6094947d0b0@redhat.com>
Date:   Thu, 26 Sep 2019 09:42:24 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Oscar Salvador <osalvador@...e.de>,
        Alastair D'Silva <alastair@....ibm.com>
Cc:     alastair@...ilva.org, Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.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 26.09.19 09:40, Oscar Salvador wrote:
> 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?

At least devmem/memremap needs special handling.

> 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. 
> 


-- 

Thanks,

David / dhildenb