linux-kernel - Re: [RFC PATCH v2 23/27] mm/mmap: Add IBT bitmap size to address space limit check

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Date:   Wed, 11 Jul 2018 09:56:27 -0700
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, 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>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <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" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>
Subject: Re: [RFC PATCH v2 23/27] mm/mmap: Add IBT bitmap size to address
 space limit check

On Tue, 2018-07-10 at 16:57 -0700, Dave Hansen wrote:
> On 07/10/2018 03:26 PM, Yu-cheng Yu wrote:
> > 
> > The indirect branch tracking legacy bitmap takes a large address
> > space.  This causes may_expand_vm() failure on the address limit
> > check.  For a IBT-enabled task, add the bitmap size to the
> > address limit.
> This appears to require that we set up
> current->thread.cet.ibt_bitmap_size _before_ calling may_expand_vm().
> What keeps the ibt_mmap() itself from hitting the address limit?

Yes, that is overlooked.  I will fix it.

Thanks,
Yu-cheng