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Open Source and information security mailing list archives
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Date: Thu, 30 Aug 2018 19:59:32 +0200 From: Jann Horn <jannh@...gle.com> To: yu-cheng.yu@...el.com Cc: Dave Hansen <dave.hansen@...ux.intel.com>, "the arch/x86 maintainers" <x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, kernel list <linux-kernel@...r.kernel.org>, linux-doc@...r.kernel.org, Linux-MM <linux-mm@...ck.org>, linux-arch <linux-arch@...r.kernel.org>, Linux API <linux-api@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>, Andy Lutomirski <luto@...capital.net>, Balbir Singh <bsingharora@...il.com>, Cyrill Gorcunov <gorcunov@...il.com>, Florian Weimer <fweimer@...hat.com>, hjl.tools@...il.com, Jonathan Corbet <corbet@....net>, keescook@...omiun.org, Mike Kravetz <mike.kravetz@...cle.com>, Nadav Amit <nadav.amit@...il.com>, Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>, Peter Zijlstra <peterz@...radead.org>, ravi.v.shankar@...el.com, vedvyas.shanbhogue@...el.com Subject: Re: [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW On Thu, Aug 30, 2018 at 7:58 PM Yu-cheng Yu <yu-cheng.yu@...el.com> wrote: > > On Thu, 2018-08-30 at 10:33 -0700, Dave Hansen wrote: > > On 08/30/2018 10:26 AM, Yu-cheng Yu wrote: > > > > > > We don't have the guard page now, but there is a shadow stack > > > token > > > there, which cannot be used as a return address. > > The overall concern is that we could overflow into a page that we > > did > > not intend. Either another actual shadow stack or something that a > > page > > that the attacker constructed, like the transient scenario Jann > > described. > > > > A task could go beyond the bottom of its shadow stack by doing either > 'ret' or 'incssp'. If it is the 'ret' case, the token prevents it. > If it is the 'incssp' case, a guard page cannot prevent it entirely, > right? I mean the other direction, on "call".
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