linux-kernel - Re: [PATCH] x86/sgx: fix a NULL pointer

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Message-ID: <op.18b0u6evwjvjmi@hhuan26-mobl.amr.corp.intel.com>
Date:   Wed, 19 Jul 2023 08:53:20 -0500
From:   "Haitao Huang" <haitao.huang@...ux.intel.com>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "hpa@...or.com" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Dave Hansen" <dave.hansen@...el.com>
Cc:     "kristen@...ux.intel.com" <kristen@...ux.intel.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "Christopherson,, Sean" <seanjc@...gle.com>
Subject: Re: [PATCH] x86/sgx: fix a NULL pointer

Hi Dave and Kai
On Tue, 18 Jul 2023 19:21:54 -0500, Dave Hansen <dave.hansen@...el.com>  
wrote:

> On 7/18/23 17:14, Huang, Kai wrote:
>> Also perhaps the patch title is too vague.  Adding more information  
>> doesn't hurt
>> I think, e.g., mentioning it is a fix for NULL pointer dereference in  
>> the EAUG
>> flow.
>
> Yeah, let's say something like:
>
> 	x86/sgx: Resolve SECS reclaim vs. page fault race
>
The patch is not to resolve SECS vs #PF race though the race is a  
necessary condition to cause the NULL pointer. The same condition does not  
cause NULL pointer in the ELDU path of #PF, only in EAUG path of #PF.

And the issue really is the NULL pointer not checked and fix was to reuse  
the same code to reload SECS in ELDU code path for EAUG code path


How about this:

x86/sgx:  Reload reclaimed SECS for EAUG on #PF

or

x86/sgx: Fix a NULL pointer to SECS used for EAUG on #PF

BR
Haitao