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

From: "H.J. Lu" <hjl.tools@gmail.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>,
	Balbir Singh <bsingharora@gmail.com>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Eugene Syromiatnikov <esyr@redhat.com>,
	Florian Weimer <fweimer@redhat.com>, Jann Horn <jannh@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Nadav Amit <nadav.amit@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	Peter Zijlstra <peterz@infradead.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Weijiang Yang <weijiang.yang@intel.com>,
	Pengfei Xu <pengfei.xu@intel.com>,
	Haitao Huang <haitao.huang@intel.com>,
	Rick P Edgecombe <rick.p.edgecombe@intel.com>
Subject: Re: [PATCH v29 25/32] x86/cet/shstk: Handle thread shadow stack
Date: Thu, 26 Aug 2021 10:22:29 -0700	[thread overview]
Message-ID: <CAMe9rOoo5wC7AWbo3WO_GWvT5CXV3r3ysZ2qB8ZPi=giRBDetg@mail.gmail.com> (raw)
In-Reply-To: <YSfGUlGJdV/5EcBs@zn.tnic>

On Thu, Aug 26, 2021 at 9:49 AM Borislav Petkov <bp@alien8.de> wrote:
>
> 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()"?

clone() doesn't have stack size info which was added to clone3().

> > +      * cap to 4 GB.
> > +      */
>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette

-- 
H.J.