linux-kernel - Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c1b0019d-d3cb-cc62-f47f-90c2550c22a4@intel.com>
Date:   Mon, 28 Sep 2020 08:43:16 -0700
From:   "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
To:     Andrew Cooper <andrew.cooper3@...rix.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        x86@...nel.org, linux-sgx@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        Jethro Beekman <jethro@...tanix.com>,
        Cedric Xing <cedric.xing@...el.com>, akpm@...ux-foundation.org,
        andriy.shevchenko@...ux.intel.com, asapek@...gle.com, bp@...en8.de,
        chenalexchen@...gle.com, conradparker@...gle.com,
        cyhanish@...gle.com, dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, luto@...nel.org,
        nhorman@...hat.com, npmccallum@...hat.com, puiterwijk@...hat.com,
        rientjes@...gle.com, tglx@...utronix.de, yaozhangx@...gle.com,
        "H.J. Lu" <hjl.tools@...il.com>
Subject: Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX
 enclave call

On 9/25/2020 11:23 AM, Andrew Cooper wrote:
> On 15/09/2020 12:28, Jarkko Sakkinen wrote:
>> diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S
>> new file mode 100644
>> index 000000000000..adbd59d41517
>> --- /dev/null
>> +++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S
>> @@ -0,0 +1,157 @@
>> +SYM_FUNC_START(__vdso_sgx_enter_enclave)
>> <snip>
>> +.Lretpoline:
>> +	call	2f
>> +1:	pause
>> +	lfence
>> +	jmp	1b
>> +2:	mov	%rax, (%rsp)
>> +	ret
> 
> I hate to throw further spanners in the work, but this is not compatible
> with CET, and the user shadow stack work in progress.

Hi Jarkko,

These 1: and 2: targets are reached only from these few lines?  If they 
are direct call/jmp targets, I think it is OK in terms of CET.  If they 
are reached from an instruction like "jmp *%rax", then we need to put in 
an "endbr64".

Yu-cheng

> 
> Whichever of these two large series lands first is going to inflict
> fixing this problem on the other.
> 
> As the vdso text is global (to a first approximation), it must not be a
> retpoline if any other process is liable to want to use CET-SS.
> 
> If the retpoline really does need to stay, then the vdso probably needs
> to gain suitable __x86_indirect_thunk_%reg thunks which are patched at
> boot based on the system properties.
> 
> ~Andrew
>