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Date:   Tue, 18 Jul 2023 07:27:49 -0700
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Subject: Re: [PATCH] x86/sgx: fix a NULL pointer
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To:     Haitao Huang <haitao.huang@linux.intel.com>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        dave.hansen@linux.intel.com, linux-kernel@vger.kernel.org,
        linux-sgx@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Cc:     kai.huang@intel.com, reinette.chatre@intel.com,
        kristen@linux.intel.com, seanjc@google.com, stable@vger.kernel.org
References: <CU4OBQ8MQ2LK.2GRBPLQGVTZ3@seitikki>
 <20230717202938.94989-1-haitao.huang@linux.intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
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On 7/17/23 13:29, Haitao Huang wrote:
> Under heavy load, the SGX EPC reclaimers (current ksgxd or future EPC
> cgroup worker) may reclaim the SECS EPC page for an enclave and set
> encl->secs.epc_page to NULL. But the SECS EPC page is used for EAUG in
> the SGX #PF handler without checking for NULL and reloading.
> 
> Fix this by checking if SECS is loaded before EAUG and load it if it was
> reclaimed.

It would be nice to see a _bit_ more theory of the bug in here.

What is an SECS page and why is it special in a reclaim context?  Why is
this so hard to hit?  What led you to discover this issue now?  What is
EAUG?