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

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Date:   Fri, 21 Jul 2023 00:52:22 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "Hansen, Dave" <dave.hansen@...el.com>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "hpa@...or.com" <hpa@...or.com>,
        "haitao.huang@...ux.intel.com" <haitao.huang@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
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

On Fri, 2023-07-21 at 00:32 +0000, Huang, Kai wrote:
> On Wed, 2023-07-19 at 08:53 -0500, Haitao Huang wrote:
> > 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
> > 
> 
> Perhaps you can add "EAUG" part to what Dave suggested?
> 
> 	x86/sgx: Resolves SECS reclaim vs. page fault race on EAUG
> 
> (assuming Dave is fine with this :-))

Btw, do you have a real call trace?  If you have, I think you can add that to
the changelog too because that catches people's eye immediately.