linux-kernel - Re: [PATCH v14 09/19] x86/mm: x86/sgx: Signal SEGV_SGXERR for #PFs w/ PF

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: <d0e47333-18b9-51c3-7d79-f27d6005f24f@intel.com>
Date:   Thu, 27 Sep 2018 07:58:41 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        nhorman@...hat.com, npmccallum@...hat.com,
        "Ayoun, Serge" <serge.ayoun@...el.com>, shay.katz-zamir@...el.com,
        linux-sgx@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v14 09/19] x86/mm: x86/sgx: Signal SEGV_SGXERR for #PFs w/
 PF_SGX

On 09/27/2018 06:42 AM, Jarkko Sakkinen wrote:
>> 	This flag is 1 if the exception is unrelated to paging and
>> 	resulted from violation of SGX-specific access-control
>> 	requirements. ... such a violation can occur only if there
>> 	is no ordinary page fault...
>>
>> This is pretty important.  It means that *none* of the other
>> paging-related stuff that we're doing applies.
>>
>> We also need to clarify how this can happen.  Is it through something
>> than an app does, or is it solely when the hardware does something under
>> the covers, like suspend/resume.
> When you change page permissions lets say with mprotect after the and
> try to do an invalid access according to the EPCM permissions this can
> happen.

So, there are pages that are non-executable, non-readable, or
non-writable both via the page tables and via underlying SGX
permissions.  Then, we allow an mprotect() and a later access will
result in one of these SGX faults?

What permissions are these, exactly?  Is it even a good idea to let that
mprotect() go through in the first place?

Either way, it sounds like we have some new conditions to spell out in
that comment.