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Date:   Thu, 21 Jan 2021 02:29:42 +0200
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Sean Christopherson <seanjc@google.com>
Cc:     linux-sgx@vger.kernel.org, dave.hansen@intel.com,
        kai.huang@intel.com, haitao.huang@intel.com,
        stable@vger.kernel.org,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Jethro Beekman <jethro@fortanix.com>
Subject: Re: [PATCH v4] x86/sgx: Fix the call order of synchronize_srcu() in
 sgx_release()
Message-ID: <YAjK9n6zct2VTp74@kernel.org>
References: <20210115014638.15037-1-jarkko@kernel.org>
 <YAhp4Jrj6hIcvgRC@google.com>
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On Wed, Jan 20, 2021 at 09:35:28AM -0800, Sean Christopherson wrote:
> On Fri, Jan 15, 2021, jarkko@kernel.org wrote:
> > From: Jarkko Sakkinen <jarkko@kernel.org>
> > 
> > The most trivial example of a race condition can be demonstrated with this
> > example where mm_list contains just one entry:
> > 
> > CPU A                   CPU B
> > sgx_release()
> >                         sgx_mmu_notifier_release()
> >                         list_del_rcu()
> > sgx_encl_release()
> >                         synchronize_srcu()
> > cleanup_srcu_struct()
> > 
> > To fix this, call synchronize_srcu() before checking whether mm_list is
> > empty in sgx_release().
> 
> Why haven't you included the splat that Haitao provided?  That would go a long
> way to helping answer Boris' question about exactly what is broken...

I've lost the klog.

/Jarkko