From: Andy Lutomirski <luto@amacapital.net>
To: Kees Cook <keescook@google.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
X86 ML <x86@kernel.org>, Linux-MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Dave Hansen <dave@sr71.net>
Subject: Re: [PATCH 33/33] x86, pkeys: execute-only support
Date: Wed, 17 Feb 2016 14:17:45 -0800 [thread overview]
Message-ID: <CALCETrVUifty6QuXo67zt9DuxsgUPTqzFbaKGS0qXd75jAb35Q@mail.gmail.com> (raw)
In-Reply-To: <CAGXu5j+L6W17wkKNdheUQQ01bJE4ZXLDiG=5JBaNWju2j9NB2Q@mail.gmail.com>
On Feb 17, 2016 1:27 PM, "Kees Cook" <keescook@google.com> wrote:
>
> On Fri, Feb 12, 2016 at 1:02 PM, Dave Hansen <dave@sr71.net> wrote:
> >
> > From: Dave Hansen <dave.hansen@linux.intel.com>
> >
> > Protection keys provide new page-based protection in hardware.
> > But, they have an interesting attribute: they only affect data
> > accesses and never affect instruction fetches. That means that
> > if we set up some memory which is set as "access-disabled" via
> > protection keys, we can still execute from it.
> >
> > This patch uses protection keys to set up mappings to do just that.
> > If a user calls:
> >
> > mmap(..., PROT_EXEC);
> > or
> > mprotect(ptr, sz, PROT_EXEC);
> >
> > (note PROT_EXEC-only without PROT_READ/WRITE), the kernel will
> > notice this, and set a special protection key on the memory. It
> > also sets the appropriate bits in the Protection Keys User Rights
> > (PKRU) register so that the memory becomes unreadable and
> > unwritable.
> >
> > I haven't found any userspace that does this today. With this
> > facility in place, we expect userspace to move to use it
> > eventually. Userspace _could_ start doing this today. Any
> > PROT_EXEC calls get converted to PROT_READ inside the kernel, and
> > would transparently be upgraded to "true" PROT_EXEC with this
> > code. IOW, userspace never has to do any PROT_EXEC runtime
> > detection.
>
> Random thought while skimming email:
>
> Is there a way to detect this feature's availability without userspace
> having to set up a segv handler and attempting to read a
> PROT_EXEC-only region? (i.e. cpu flag for protection keys, or a way to
> check the protection to see if PROT_READ got added automatically,
> etc?)
>
We could add an HWCAP.
--Andy
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next prev parent reply other threads:[~2016-02-17 22:18 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-12 21:01 [PATCH 00/33] x86: Memory Protection Keys (v10) Dave Hansen
2016-02-12 21:01 ` [PATCH 01/33] mm: introduce get_user_pages_remote() Dave Hansen
2016-02-15 6:09 ` Balbir Singh
2016-02-15 16:29 ` Dave Hansen
2016-02-15 6:14 ` Srikar Dronamraju
2016-02-12 21:01 ` [PATCH 02/33] mm: overload get_user_pages() functions Dave Hansen
2016-02-16 8:36 ` Ingo Molnar
2016-02-17 18:15 ` Dave Hansen
2016-02-12 21:01 ` [PATCH 03/33] mm, gup: switch callers of get_user_pages() to not pass tsk/mm Dave Hansen
2016-02-12 21:01 ` [PATCH 04/33] x86, fpu: add placeholder for Processor Trace XSAVE state Dave Hansen
2016-02-12 21:02 ` [PATCH 05/33] x86, pkeys: Add Kconfig option Dave Hansen
2016-02-12 21:02 ` [PATCH 06/33] x86, pkeys: cpuid bit definition Dave Hansen
2016-02-12 21:02 ` [PATCH 07/33] x86, pkeys: define new CR4 bit Dave Hansen
2016-02-12 21:02 ` [PATCH 08/33] x86, pkeys: add PKRU xsave fields and data structure(s) Dave Hansen
2016-02-12 21:02 ` [PATCH 09/33] x86, pkeys: PTE bits for storing protection key Dave Hansen
2016-02-12 21:02 ` [PATCH 10/33] x86, pkeys: new page fault error code bit: PF_PK Dave Hansen
2016-02-12 21:02 ` [PATCH 11/33] x86, pkeys: store protection in high VMA flags Dave Hansen
2016-02-12 21:02 ` [PATCH 12/33] x86, pkeys: arch-specific protection bits Dave Hansen
2016-02-12 21:02 ` [PATCH 13/33] x86, pkeys: pass VMA down in to fault signal generation code Dave Hansen
2016-02-12 21:02 ` [PATCH 14/33] signals, pkeys: notify userspace about protection key faults Dave Hansen
2016-02-12 21:02 ` [PATCH 15/33] x86, pkeys: fill in pkey field in siginfo Dave Hansen
2016-02-12 21:02 ` [PATCH 16/33] x86, pkeys: add functions to fetch PKRU Dave Hansen
2016-02-12 21:02 ` [PATCH 17/33] mm: factor out VMA fault permission checking Dave Hansen
2016-02-12 21:02 ` [PATCH 18/33] x86, mm: simplify get_user_pages() PTE bit handling Dave Hansen
2016-02-12 21:02 ` [PATCH 19/33] x86, pkeys: check VMAs and PTEs for protection keys Dave Hansen
2016-02-12 21:02 ` [PATCH 20/33] mm: do not enforce PKEY permissions on "foreign" mm access Dave Hansen
2016-02-12 21:02 ` [PATCH 21/33] x86, pkeys: optimize fault handling in access_error() Dave Hansen
2016-02-12 21:02 ` [PATCH 22/33] x86, pkeys: differentiate instruction fetches Dave Hansen
2016-02-12 21:02 ` [PATCH 23/33] x86, pkeys: dump PKRU with other kernel registers Dave Hansen
2016-02-12 21:02 ` [PATCH 24/33] x86, pkeys: dump pkey from VMA in /proc/pid/smaps Dave Hansen
2016-02-12 21:02 ` [PATCH 25/33] x86, pkeys: add Kconfig prompt to existing config option Dave Hansen
2016-02-12 21:02 ` [PATCH 26/33] x86, pkeys: actually enable Memory Protection Keys in CPU Dave Hansen
2016-02-12 21:02 ` [PATCH 27/33] mm, multi-arch: pass a protection key in to calc_vm_flag_bits() Dave Hansen
2016-02-12 21:02 ` [PATCH 28/33] x86, pkeys: add arch_validate_pkey() Dave Hansen
2016-02-12 21:02 ` [PATCH 29/33] x86: separate out LDT init from context init Dave Hansen
2016-02-12 21:02 ` [PATCH 30/33] x86, fpu: allow setting of XSAVE state Dave Hansen
2016-02-12 21:02 ` [PATCH 31/33] x86, pkeys: allow kernel to modify user pkey rights register Dave Hansen
2016-02-12 21:02 ` [PATCH 32/33] x86, pkeys: create an x86 arch_calc_vm_prot_bits() for VMA flags Dave Hansen
2016-02-12 21:02 ` [PATCH 33/33] x86, pkeys: execute-only support Dave Hansen
2016-02-17 21:27 ` Kees Cook
2016-02-17 21:33 ` Dave Hansen
2016-02-17 21:36 ` Kees Cook
2016-02-17 22:17 ` Andy Lutomirski [this message]
2016-02-17 22:53 ` Dave Hansen
2016-02-18 0:46 ` Andy Lutomirski
2016-02-16 9:29 ` [PATCH 00/33] x86: Memory Protection Keys (v10) Ingo Molnar
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