linux-kernel - Re: [PATCH v29 25/32] x86/cet/shstk: Handle thread shadow stack

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Message-ID: <YSfGUlGJdV/5EcBs@zn.tnic>
Date:   Thu, 26 Aug 2021 18:50:26 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     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@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.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@...omium.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>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>,
        Rick P Edgecombe <rick.p.edgecombe@...el.com>
Subject: Re: [PATCH v29 25/32] x86/cet/shstk: Handle thread shadow stack

On Fri, Aug 20, 2021 at 11:11:54AM -0700, Yu-cheng Yu wrote:
> diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
> index 5993aa8db338..7c1ca2476a5e 100644
> --- a/arch/x86/kernel/shstk.c
> +++ b/arch/x86/kernel/shstk.c
> @@ -75,6 +75,61 @@ int shstk_setup(void)
>  	return err;
>  }
>  
> +int shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags,
> +			     unsigned long stack_size)
> +{
> +	struct thread_shstk *shstk = &tsk->thread.shstk;
> +	struct cet_user_state *state;
> +	unsigned long addr;
> +
> +	if (!shstk->size)
> +		return 0;
> +
> +	/*
> +	 * Earlier clone() does not pass stack_size.  Use RLIMIT_STACK and

What is "earlier clone()"?

> +	 * cap to 4 GB.
> +	 */

-- 
Regards/Gruss,
    Boris.

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