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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Andy Lutomirski <luto@amacapital.net>,
        Borislav Petkov <bp@alien8.de>
Cc:     Sean Christopherson <sean.j.christopherson@intel.com>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        X86 ML <x86@kernel.org>, linux-sgx@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Jethro Beekman <jethro@fortanix.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        asapek@google.com, "Xing\, Cedric" <cedric.xing@intel.com>,
        chenalexchen@google.com, conradparker@google.com,
        cyhanish@google.com, Dave Hansen <dave.hansen@intel.com>,
        "Huang\, Haitao" <haitao.huang@intel.com>,
        Josh Triplett <josh@joshtriplett.org>,
        "Huang\, Kai" <kai.huang@intel.com>,
        "Svahn\, Kai" <kai.svahn@intel.com>, kmoy@google.com,
        Christian Ludloff <ludloff@google.com>,
        Andrew Lutomirski <luto@kernel.org>,
        Neil Horman <nhorman@redhat.com>, npmccallum@redhat.com,
        puiterwijk@redhat.com, David Rientjes <rientjes@google.com>,
        yaozhangx@google.com
Subject: Re: [PATCH v33 15/21] x86/vdso: Add support for exception fixup in vDSO functions
In-Reply-To: <CALCETrWUHw2WSDaJrxrwVrXSGz-zR0N2R3cT06esKBCpqyoZaQ@mail.gmail.com>
References: <20200617220844.57423-1-jarkko.sakkinen@linux.intel.com> <20200617220844.57423-16-jarkko.sakkinen@linux.intel.com> <20200629171022.GC32176@zn.tnic> <20200630060055.GS12312@linux.intel.com> <20200630084128.GA1093@zn.tnic> <CALCETrWUHw2WSDaJrxrwVrXSGz-zR0N2R3cT06esKBCpqyoZaQ@mail.gmail.com>
Date:   Thu, 02 Jul 2020 14:52:25 +0200
Message-ID: <87mu4i9j06.fsf@nanos.tec.linutronix.de>
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Andy Lutomirski <luto@amacapital.net> writes:
> On Tue, Jun 30, 2020 at 1:41 AM Borislav Petkov <bp@alien8.de> wrote:
>>
>> On Mon, Jun 29, 2020 at 11:00:55PM -0700, Sean Christopherson wrote:
>> > E.g. the vDSO function should get the fixup even if userspace screws
>> > up mmap() and invokes __vdso_sgx_enter_enclave() without being tagged
>> > an SGX task.
>>
>> I sincerely hope you don't mean this seriously.
>>
>> Please add a member to task_struct which denotes that a task is an
>> sgx task, test that member where needed and forget real quickly about
>> running *any* *fixup* for unrelated tasks.
>
> I don't see the problem.  If you call this magic vDSO function and get
> a fault, it gets handled.  What's the failure mode?

Handled by some definition of handled. If a random user space tasks ends
up in that function then it will not die as it would otherwise, but I
don't see a real issue with that either.

Thanks,

        tglx