Re: [PATCH v10 1/3] x86/syscalls: Check address limit on user-mode return

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v10 1/3] x86/syscalls: Check address limit on user-mode return
Date	2017-07-06 23:00 +0200
Message-ID	<u0m2t-2hh-17@gated-at.bofh.it> (permalink)
References	<tSrC1-4gc-3@gated-at.bofh.it> <tUxWG-4Sn-7@gated-at.bofh.it> <tXpq1-t5-145@gated-at.bofh.it> <u0lJ7-2av-5@gated-at.bofh.it>
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On Thu, 6 Jul 2017, Thomas Garnier wrote:
> On Wed, Jun 28, 2017 at 10:52 AM, Kees Cook <keescook@chromium.org> wrote:
> >
> > On Tue, Jun 20, 2017 at 1:24 PM, Kees Cook <keescook@chromium.org> wrote:
> > > On Wed, Jun 14, 2017 at 6:12 PM, Thomas Garnier <thgarnie@google.com> wrote:
> > >> Ensure the address limit is a user-mode segment before returning to
> > >> user-mode. Otherwise a process can corrupt kernel-mode memory and elevate
> > >> privileges [1].
> > >>
> > >> The set_fs function sets the TIF_SETFS flag to force a slow path on
> > >> return. In the slow path, the address limit is checked to be USER_DS if
> > >> needed.
> > >>
> > >> The addr_limit_user_check function is added as a cross-architecture
> > >> function to check the address limit.
> > >>
> > >> [1] https://bugs.chromium.org/p/project-zero/issues/detail?id=990
> > >>
> > >> Signed-off-by: Thomas Garnier <thgarnie@google.com>
> > >
> > > Thanks for reworking this series!
> > >
> > > The bad state correctly BUGs under the LKDTM test:
> > >
> > > [   21.171586] lkdtm: Performing direct entry CORRUPT_USER_DS
> > > [   21.172791] lkdtm: setting bad task size limit
> > > [   21.173742] ------------[ cut here ]------------
> > > [   21.174641] kernel BUG at ./include/linux/syscalls.h:220!
> > > ...
> > > [   21.193166] Call Trace:
> > > [   21.193617]  ? trace_hardirqs_on_thunk+0x1a/0x1c
> > > [   21.194443]  entry_SYSCALL64_slow_path+0x25/0x25
> > >
> > >
> > > Tested-by: Kees Cook <keescook@chromium.org>
> >
> > Is everyone happy with this patch for x86? Does this need anything
> > more/different?
> 
> Asking again. Additional feedback? Anyone wants to pick-it up?

Can do. This needs to be a combo of all 3 I assume as the x86 one contains
the function used by all of them, right?

Thanks,

	tglx

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Re: [PATCH v10 1/3] x86/syscalls: Check address limit on user-mode return Thomas Garnier <thgarnie@google.com> - 2017-07-06 22:40 +0200
  Re: [PATCH v10 1/3] x86/syscalls: Check address limit on user-mode return Thomas Garnier <thgarnie@google.com> - 2017-07-06 23:00 +0200
  Re: [PATCH v10 1/3] x86/syscalls: Check address limit on user-mode  return Thomas Gleixner <tglx@linutronix.de> - 2017-07-06 23:00 +0200

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