linux-kernel - Re: [RFC 1/2] slub: Avoid trying to allocate memory on offline nodes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c6caddbf-e275-219e-12b6-538a53ced17d@arm.com>
Date:   Thu, 2 Aug 2018 22:21:53 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, vbabka@...e.cz, Punit.Agrawal@....com,
        Lorenzo.Pieralisi@....com, linux-arm-kernel@...ts.infradead.org,
        bhelgaas@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC 1/2] slub: Avoid trying to allocate memory on offline nodes

Hi,

On 08/02/2018 04:15 AM, Michal Hocko wrote:
> On Wed 01-08-18 15:04:17, Jeremy Linton wrote:
> [...]
>> @@ -2519,6 +2519,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>>   		if (unlikely(!node_match(page, searchnode))) {
>>   			stat(s, ALLOC_NODE_MISMATCH);
>>   			deactivate_slab(s, page, c->freelist, c);
>> +			if (!node_online(searchnode))
>> +				node = NUMA_NO_NODE;
>>   			goto new_slab;
> 
> This is inherently racy. Numa node can get offline at any point after
> you check it here. Making it race free would involve some sort of
> locking and I am not really convinced this is a good idea.

I spent some time looking/thinking about this, and i'm pretty sure its 
not creating any new problems. But OTOH, I think the node_online() check 
is probably a bit misleading as what we really want to assure is that 
node<MAX_NUMNODES and that there is going to be a valid entry in 
NODE_DATA() so we don't deference null.


> 
>>   		}
>>   	}
>> -- 
>> 2.14.3
>>
>