From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: bsingharora@gmail.com, LKML <linux-kernel@vger.kernel.org>,
linux-doc@vger.kernel.org, Linux-MM <linux-mm@kvack.org>,
linux-arch <linux-arch@vger.kernel.org>, X86 ML <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. J. Lu" <hjl.tools@gmail.com>,
"Shanbhogue, Vedvyas" <vedvyas.shanbhogue@intel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Jonathan Corbet <corbet@lwn.net>, Oleg Nesterov <oleg@redhat.com>,
Arnd Bergmann <arnd@arndb.de>,
mike.kravetz@oracle.com
Subject: Re: [PATCH 00/10] Control Flow Enforcement - Part (3)
Date: Tue, 12 Jun 2018 13:15:38 -0700 [thread overview]
Message-ID: <1528834538.9849.13.camel@2b52.sc.intel.com> (raw)
In-Reply-To: <1528824280.9447.30.camel@2b52.sc.intel.com>
On Tue, 2018-06-12 at 10:24 -0700, Yu-cheng Yu wrote:
> On Tue, 2018-06-12 at 09:31 -0700, Andy Lutomirski wrote:
> > On Tue, Jun 12, 2018 at 9:24 AM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
> > >
> > > On Tue, 2018-06-12 at 09:00 -0700, Andy Lutomirski wrote:
> > > > On Tue, Jun 12, 2018 at 8:06 AM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
> > > > >
> > > > > On Tue, 2018-06-12 at 20:56 +1000, Balbir Singh wrote:
> > > > > >
> > > > > > On 08/06/18 00:37, Yu-cheng Yu wrote:
> > > > > > > This series introduces CET - Shadow stack
> > > > > > >
> > > > > > > At the high level, shadow stack is:
> > > > > > >
> > > > > > > Allocated from a task's address space with vm_flags VM_SHSTK;
> > > > > > > Its PTEs must be read-only and dirty;
> > > > > > > Fixed sized, but the default size can be changed by sys admin.
> > > > > > >
> > > > > > > For a forked child, the shadow stack is duplicated when the next
> > > > > > > shadow stack access takes place.
> > > > > > >
> > > > > > > For a pthread child, a new shadow stack is allocated.
> > > > > > >
> > > > > > > The signal handler uses the same shadow stack as the main program.
> > > > > > >
> > > > > >
> > > > > > Even with sigaltstack()?
> > > > > >
> > > > > >
> > > > > > Balbir Singh.
> > > > >
> > > > > Yes.
> > > > >
> > > >
> > > > I think we're going to need some provision to add an alternate signal
> > > > stack to handle the case where the shadow stack overflows.
> > >
> > > The shadow stack stores only return addresses; its consumption will not
> > > exceed a percentage of (program stack size + sigaltstack size) before
> > > those overflow. When that happens, there is usually very little we can
> > > do. So we set a default shadow stack size that supports certain nested
> > > calls and allow sys admin to adjust it.
> > >
> >
> > Of course there's something you can do: add a sigaltstack-like stack
> > switching mechanism. Have a reserve shadow stack and, when a signal
> > is delivered (possibly guarded by other conditions like "did the
> > shadow stack overflow"), switch to a new shadow stack and maybe write
> > a special token to the new shadow stack that says "signal delivery
> > jumped here and will restore to the previous shadow stack and
> > such-and-such address on return".
>
> If (shstk size == (stack size + sigaltstack size)), then shstk will not
> overflow before program stack overflows and sigaltstack also overflows.
>
> Let me think about this.
The reserve shadow stack will help only when the shstk overflows but
signal stack/sigaltstack still has room and we can deliver a signal. If
the shstk is large enough to cover any nested calls that will overflow
both the program stack and sigaltstack then we don't need a reserve
shstk.
We can estimate how big the shstk needs to be; in the worst case it
should not be greater than (program stack size + sigaltstack size). The
default shstk size we choose pass all signal tests in GLIBC. In case
there is a need to increase it for a very large RLIMIT_STACK or very
large sigaltstack, the sys admin can increase the default shstk size.
Yu-cheng
next prev parent reply other threads:[~2018-06-12 20:18 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-07 14:37 [PATCH 00/10] Control Flow Enforcement - Part (3) Yu-cheng Yu
2018-06-07 14:37 ` [PATCH 01/10] x86/cet: User-mode shadow stack support Yu-cheng Yu
2018-06-07 16:37 ` Andy Lutomirski
2018-06-07 17:46 ` Yu-cheng Yu
2018-06-07 17:55 ` Dave Hansen
2018-06-07 18:23 ` Andy Lutomirski
2018-06-12 11:56 ` Balbir Singh
2018-06-12 15:03 ` Yu-cheng Yu
2018-06-07 14:37 ` [PATCH 02/10] x86/cet: Introduce WRUSS instruction Yu-cheng Yu
2018-06-07 16:40 ` Andy Lutomirski
2018-06-07 16:51 ` Yu-cheng Yu
2018-06-07 18:41 ` Peter Zijlstra
2018-06-07 20:31 ` Yu-cheng Yu
2018-06-11 8:17 ` Peter Zijlstra
2018-06-11 15:02 ` Yu-cheng Yu
2018-06-14 1:30 ` Balbir Singh
2018-06-14 14:43 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 03/10] x86/cet: Signal handling for shadow stack Yu-cheng Yu
2018-06-07 18:30 ` Andy Lutomirski
2018-06-07 18:58 ` Florian Weimer
2018-06-07 19:51 ` Yu-cheng Yu
2018-06-07 20:07 ` Cyrill Gorcunov
2018-06-07 20:57 ` Andy Lutomirski
2018-06-08 12:07 ` Cyrill Gorcunov
2018-06-07 20:12 ` Yu-cheng Yu
2018-06-07 20:17 ` Dave Hansen
2018-06-07 14:38 ` [PATCH 04/10] x86/cet: Handle thread " Yu-cheng Yu
2018-06-07 18:21 ` Andy Lutomirski
2018-06-07 19:47 ` Florian Weimer
2018-06-07 20:53 ` Andy Lutomirski
2018-06-08 14:53 ` Florian Weimer
2018-06-08 15:01 ` Andy Lutomirski
2018-06-08 15:50 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 05/10] x86/cet: ELF header parsing of Control Flow Enforcement Yu-cheng Yu
2018-06-07 18:38 ` Andy Lutomirski
2018-06-07 20:40 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 06/10] x86/cet: Add arch_prctl functions for shadow stack Yu-cheng Yu
2018-06-07 18:48 ` Andy Lutomirski
2018-06-07 20:30 ` Yu-cheng Yu
2018-06-07 21:01 ` Andy Lutomirski
2018-06-07 22:02 ` H.J. Lu
2018-06-07 23:01 ` Andy Lutomirski
2018-06-08 4:09 ` H.J. Lu
2018-06-08 4:38 ` Andy Lutomirski
2018-06-08 12:24 ` H.J. Lu
2018-06-08 14:57 ` Andy Lutomirski
2018-06-08 15:52 ` Cyrill Gorcunov
2018-06-08 4:22 ` H.J. Lu
2018-06-08 4:35 ` Andy Lutomirski
2018-06-08 12:17 ` H.J. Lu
2018-06-12 10:03 ` Thomas Gleixner
2018-06-12 11:43 ` H.J. Lu
2018-06-12 16:01 ` Andy Lutomirski
2018-06-12 16:05 ` H.J. Lu
2018-06-12 16:34 ` Andy Lutomirski
2018-06-12 16:51 ` H.J. Lu
2018-06-12 18:59 ` Thomas Gleixner
2018-06-12 19:34 ` H.J. Lu
2018-06-18 22:03 ` Andy Lutomirski
2018-06-19 0:52 ` Kees Cook
2018-06-19 6:40 ` Florian Weimer
2018-06-19 14:50 ` Andy Lutomirski
2018-06-19 16:44 ` Kees Cook
2018-06-19 16:59 ` Yu-cheng Yu
2018-06-19 17:07 ` Kees Cook
2018-06-19 17:20 ` Andy Lutomirski
2018-06-19 20:12 ` Kees Cook
2018-06-19 20:47 ` Andy Lutomirski
2018-06-19 22:38 ` Yu-cheng Yu
2018-06-20 0:50 ` Andy Lutomirski
2018-06-21 23:07 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 07/10] mm: Prevent mprotect from changing " Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 08/10] mm: Prevent mremap of " Yu-cheng Yu
2018-06-07 18:48 ` Andy Lutomirski
2018-06-07 20:18 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 09/10] mm: Prevent madvise from changing " Yu-cheng Yu
2018-06-07 20:54 ` Andy Lutomirski
2018-06-07 21:09 ` Nadav Amit
2018-06-07 21:18 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 10/10] mm: Prevent munmap and remap_file_pages of " Yu-cheng Yu
2018-06-07 18:50 ` Andy Lutomirski
2018-06-07 20:15 ` Yu-cheng Yu
2018-06-12 10:56 ` [PATCH 00/10] Control Flow Enforcement - Part (3) Balbir Singh
2018-06-12 15:03 ` Yu-cheng Yu
2018-06-12 16:00 ` Andy Lutomirski
2018-06-12 16:21 ` Yu-cheng Yu
2018-06-12 16:31 ` Andy Lutomirski
2018-06-12 17:24 ` Yu-cheng Yu
2018-06-12 20:15 ` Yu-cheng Yu [this message]
2018-06-14 1:07 ` Balbir Singh
2018-06-14 14:56 ` Yu-cheng Yu
2018-06-17 3:16 ` Balbir Singh
2018-06-18 21:44 ` Andy Lutomirski
2018-06-19 8:52 ` Balbir Singh
2018-06-26 2:46 ` Jann Horn
2018-06-26 14:56 ` Yu-cheng Yu
2018-06-26 5:26 ` Andy Lutomirski
2018-06-26 14:56 ` Yu-cheng Yu
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