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Date: Thu, 14 Dec 2017 15:10:06 +0200
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: "intel-sgx-kernel-dev@lists.01.org" 
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Subject: Re: [intel-sgx-kernel-dev] [PATCH v7 4/8] intel_sgx: driver for
 Intel Software Guard Extensions
Message-ID: <20171214131006.moogpmrugtx43qju@linux.intel.com>
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On Tue, Dec 12, 2017 at 01:46:48PM -0800, Sean Christopherson wrote:
> So it looks like you avoid the described case by moving B to the head of
> the list in sgx_eldu.  The bug I am seeing is still straightforward to
> theorize:
> 
>     1. Three VA pages.  List = A->B->C
>     2. Fill A and B, use one entry in C.  List = C->B->A
>     3. ELDU, freeing a slot in B.  List = B->C->A
>     4. EWB, consuming the last slot in B.  List = B->C->A
>     5. ELDU, freeing a slot in A.  List = A->B->C
>     6. EWB, consuming the last slot in A.  List = A->B->C
>     7. ELDU, but both A and B are full
>     8. Explode

I see. It is easy to fix by moving back to of the list immediately after
last allocation. Thanks for pointing this out.

/Jarkko