linux-kernel - Re: staging: ion: ION allocation fall back order depends on heap linkage order

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]

Date:   Wed, 7 Feb 2018 17:10:36 +0200
From:   Alexey Skidanov <alexey.skidanov@...el.com>
To:     Laura Abbott <labbott@...hat.com>, devel@...verdev.osuosl.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: staging: ion: ION allocation fall back order depends on heap
 linkage order



On 02/07/2018 04:58 PM, Laura Abbott wrote:
> On 02/06/2018 11:05 PM, Alexey Skidanov wrote:
>>
>>
>>> Yup, you've hit upon a key problem. Having fallbacks be stable
>>> was always a problem and the recommendation these days is to
>>> not rely on them. You can specify a heap at a time and fallback
>>> manually if you want that behavior.
>>>
>>> If you have a proposal to make fallbacks work reliably without
>>> overly complicating the ABI I'm happy to review it.
>>>
>>> Thanks,
>>> Laura
>>>
>> I think it's possible to "automate" the "manual fallback" behavior. But
>> the real issues is using heap id to specify the particular heap object.
>>
>> Current API (allocation IOCTL) requires to specify the particular heap
>> object by using heap id. From the other hand, the user space doesn't
>> control the heaps creation order and heap id assignment. So it may be
>> tricky, especially when more than one object of the same heap type is
>> created automatically.
>>
>> Thanks,
>> Alexey
>>
>>
> 
> The query ioctl is designed to get the heap ID information without
> needing to rely on the linking order or anything else defined in
> the kernel.
> 
> Thanks,
> Laura

That is true. But if we have 2 *automatically created* heaps of the same
type, how userspace can distinguish between them?

Thanks,
Alexey