Intel supports faulting on the CPUID instruction beginning with Ivy Bridge.
When enabled, the processor will fault on attempts to execute the CPUID
instruction with CPL>0. This will allow a ptracer to emulate the CPUID
instruction.

Bit 31 of MSR_PLATFORM_INFO advertises support for this feature. It is
documented in detail in Section 2.3.2 of
https://bugzilla.kernel.org/attachment.cgi?id=243991

Detect support for this feature and expose it as X86_FEATURE_CPUID_FAULT.
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: linux-kselftest@vger.kernel.org
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Robert O'Callahan <robert@ocallahan.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: user-mode-linux-user@lists.sourceforge.net
Cc: David Matlack <dmatlack@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/20170320081628.18952-8-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

Hook up arch_prctl to call do_arch_prctl() on x86-32, and in 32 bit compat
mode on x86-64. This allows to have arch_prctls that are not specific to 64
bits.

On UML, simply stub out this syscall.
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: linux-kselftest@vger.kernel.org
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Robert O'Callahan <robert@ocallahan.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: user-mode-linux-user@lists.sourceforge.net
Cc: David Matlack <dmatlack@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/20170320081628.18952-7-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

Add do_arch_prctl_common() to handle arch_prctls that are not specific to 64
bit mode. Call it from the syscall entry point, but not any of the other
callsites in the kernel, which all want one of the existing 64 bit only
arch_prctls.
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: linux-kselftest@vger.kernel.org
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Robert O'Callahan <robert@ocallahan.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: user-mode-linux-user@lists.sourceforge.net
Cc: David Matlack <dmatlack@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/20170320081628.18952-6-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

In order to introduce new arch_prctls that are not 64 bit only, rename the
existing 64 bit implementation to do_arch_prctl_64(). Also rename the
second argument of that function from 'addr' to 'arg2', because it will no
longer always be an address.
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: linux-kselftest@vger.kernel.org
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Robert O'Callahan <robert@ocallahan.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Len Brown <len.brown@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: user-mode-linux-user@lists.sourceforge.net
Cc: David Matlack <dmatlack@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/20170320081628.18952-5-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

Use the SYSCALL_DEFINE2 macro instead of manually defining it.
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: linux-kselftest@vger.kernel.org
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Robert O'Callahan <robert@ocallahan.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: user-mode-linux-user@lists.sourceforge.net
Cc: David Matlack <dmatlack@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/20170320081628.18952-4-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

The x86 specific arch_prctl() arbitrarily changed prctl's 'option' to
'code'. Before adding new options, rename it.
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: linux-kselftest@vger.kernel.org
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Robert O'Callahan <robert@ocallahan.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: user-mode-linux-user@lists.sourceforge.net
Cc: David Matlack <dmatlack@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/20170320081628.18952-3-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

This matches the only public Intel documentation of this MSR, in the
"Virtualization Technology FlexMigration Application Note"
(preserved at https://bugzilla.kernel.org/attachment.cgi?id=243991)
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: linux-kselftest@vger.kernel.org
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Robert O'Callahan <robert@ocallahan.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: user-mode-linux-user@lists.sourceforge.net
Cc: David Matlack <dmatlack@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/20170320081628.18952-2-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

Provide and use a toggle helper instead of doing it with a branch.

x86_64: arch/x86/kernel/process.o
text	   data	    bss	    dec	    hex
3008	   8577	     16	  11601	   2d51 Before
2976       8577      16	  11569	   2d31 After

i386: arch/x86/kernel/process.o
text	   data	    bss	    dec	    hex
2925	   8673	      8	  11606	   2d56 Before
2893	   8673       8	  11574	   2d36 After
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Link: http://lkml.kernel.org/r/20170214081104.9244-4-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

The debug control MSR is "highly magical" as the blockstep bit can be
cleared by hardware under not well documented circumstances.

So a task switch relying on the bit set by the previous task (according to
the previous tasks thread flags) can trip over this and not update the flag
for the next task.

To fix this its required to handle DEBUGCTLMSR_BTF when either the previous
or the next or both tasks have the TIF_BLOCKSTEP flag set.

While at it avoid branching within the TIF_BLOCKSTEP case and evaluating
boot_cpu_data twice in kernels without CONFIG_X86_DEBUGCTLMSR.

x86_64: arch/x86/kernel/process.o
text	data	bss	dec	 hex
3024    8577    16      11617    2d61	Before
3008	8577	16	11601	 2d51	After

i386: No change

[ tglx: Made the shift value explicit, use a local variable to make the
code readable and massaged changelog]
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Link: http://lkml.kernel.org/r/20170214081104.9244-3-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

Help the compiler to avoid reevaluating the thread flags for each checked
bit by reordering the bit checks and providing an explicit xor for
evaluation.

With default defconfigs for each arch,

x86_64: arch/x86/kernel/process.o
text       data     bss     dec     hex
3056       8577      16   11649    2d81	Before
3024	   8577      16	  11617	   2d61	After

i386: arch/x86/kernel/process.o
text       data     bss     dec     hex
2957	   8673	      8	  11638	   2d76	Before
2925	   8673       8	  11606	   2d56	After
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Link: http://lkml.kernel.org/r/20170214081104.9244-2-khuey@kylehuey.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

Pull tty/serial fixes frpm Greg KH:
 "Here are two bugfixes for tty stuff for 4.11-rc2.

  One of them resolves the pretty bad bug in the n_hdlc code that
  Alexander Popov found and fixed and has been reported everywhere. The
  other just fixes a samsung serial driver issue when DMA fails on some
  systems.

  Both have been in linux-next with no reported issues"

* tag 'tty-4.11-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  serial: samsung: Continue to work if DMA request fails
  tty: n_hdlc: get rid of racy n_hdlc.tbuf

Pull staging driver fixes from Greg KH:
 "Here are two small build warning fixes for some staging drivers that
  Arnd has found on his valiant quest to get the kernel to build
  properly with no warnings.

  Both of these have been in linux-next this week and resolve the
  reported issues"

* tag 'staging-4.11-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  staging: octeon: remove unused variable
  staging/vc04_services: add CONFIG_OF dependency

Pull USB fixes from Greg KH:
 "Here is a number of different USB fixes for 4.11-rc2.

  Seems like there were a lot of unresolved issues that people have been
  finding for this subsystem, and a bunch of good security auditing
  happening as well from Johan Hovold. There's the usual batch of gadget
  driver fixes and xhci issues resolved as well.

 All of these have been in linux-next with no reported issues"

* tag 'usb-4.11-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (35 commits)
  usb: host: xhci-plat: Fix timeout on removal of hot pluggable xhci controllers
  usb: host: xhci-dbg: HCIVERSION should be a binary number
  usb: xhci: remove dummy extra_priv_size for size of xhci_hcd struct
  usb: xhci-mtk: check hcc_params after adding primary hcd
  USB: serial: digi_acceleport: fix OOB-event processing
  MAINTAINERS: usb251xb: remove reference inexistent file
  doc: dt-bindings: usb251xb: mark reg as required
  usb: usb251xb: dt: add unit suffix to oc-delay and power-on-time
  usb: usb251xb: remove max_{power,current}_{sp,bp} properties
  usb-storage: Add ignore-residue quirk for Initio INIC-3619
  USB: iowarrior: fix NULL-deref in write
  USB: iowarrior: fix NULL-deref at probe
  usb: phy: isp1301: Add OF device ID table
  usb: ohci-at91: Do not drop unhandled USB suspend control requests
  USB: serial: safe_serial: fix information leak in completion handler
  USB: serial: io_ti: fix information leak in completion handler
  USB: serial: omninet: drop open callback
  USB: serial: omninet: fix reference leaks at open
  USB: serial: io_ti: fix NULL-deref in interrupt callback
  usb: dwc3: gadget: make to increment req->remaining in all cases
  ...

Pull pinctrl fixes from Linus Walleij:
 "Two smaller pin control fixes for the v4.11 series:

   - Add a get_direction() function to the qcom driver

   - Fix two pin names in the uniphier driver"

* tag 'pinctrl-v4.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl:
  pinctrl: uniphier: change pin names of aio/xirq for LD11
  pinctrl: qcom: add get_direction function

Pull ceph fixes from Ilya Dryomov:

 - a fix for the recently discovered misdirected requests bug present in
   jewel and later on the server side and all stable kernels

 - a fixup for -rc1 CRUSH changes

 - two usability enhancements: osd_request_timeout option and
   supported_features bus attribute.

* tag 'ceph-for-4.11-rc2' of git://github.com/ceph/ceph-client:
  libceph: osd_request_timeout option
  rbd: supported_features bus attribute
  libceph: don't set weight to IN when OSD is destroyed
  libceph: fix crush_decode() for older maps

Pull i2c fixes from Wolfram Sang:
 "Here are some driver bugfixes from I2C.

  Unusual this time are the two reverts. One because I accidently picked
  a patch from the list which I should have pulled from my co-maintainer
  instead ("missing of_node_put"). And one which I wrongly assumed to be
  an easy fix but it turned out already that it needs more iterations
  ("copy device properties")"

* 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  Revert "i2c: copy device properties when using i2c_register_board_info()"
  Revert "i2c: add missing of_node_put in i2c_mux_del_adapters"
  i2c: exynos5: Avoid transaction timeouts due TRANSFER_DONE_AUTO not set
  i2c: designware: add reset interface
  i2c: meson: fix wrong variable usage in meson_i2c_put_data
  i2c: copy device properties when using i2c_register_board_info()
  i2c: m65xx: drop superfluous quirk structure
  i2c: brcmstb: Fix START and STOP conditions
  i2c: add missing of_node_put in i2c_mux_del_adapters
  i2c: riic: fix restart condition
  i2c: add missing of_node_put in i2c_mux_del_adapters

Pull drm fixes from Dave Airlie:
 "Intel, amd and mxsfb fixes.

  These are the drm fixes I've collected for rc2. Mostly i915 GVT only
  fixes, along with a single EDID fix, some mxsfb fixes and a few minor
  amd fixes"

* tag 'drm-fixes-for-4.11-rc2' of git://people.freedesktop.org/~airlied/linux: (38 commits)
  drm: mxsfb: Implement drm_panel handling
  drm: mxsfb_crtc: Fix the framebuffer misplacement
  drm: mxsfb: Fix crash when provided invalid DT bindings
  drm: mxsfb: fix pixel clock polarity
  drm: mxsfb: use bus_format to determine LCD bus width
  drm/amdgpu: bump driver version for some new features
  drm/amdgpu: validate paramaters in the gem ioctl
  drm/amd/amdgpu: fix console deadlock if late init failed
  drm/i915/gvt: change some gvt_err to gvt_dbg_cmd
  drm/i915/gvt: protect RO and Rsvd bits of virtual vgpu configuration space
  drm/i915/gvt: handle workload lifecycle properly
  drm/edid: Add EDID_QUIRK_FORCE_8BPC quirk for Rotel RSX-1058
  drm/i915/gvt: fix an error for F_RO flag
  drm/i915/gvt: use pfn_valid for better checking
  drm/i915/gvt: set SFUSE_STRAP properly for vitual monitor detection
  drm/i915/gvt: fix an error for one register
  drm/i915/gvt: add more registers into handlers list
  drm/i915/gvt: have more registers with F_CMD_ACCESS flags set
  drm/i915/gvt: add some new MMIOs to cmd_access white list
  drm/i915/gvt: fix pcode mailbox write emulation of BDW
  ...

Merge 5-level page table prep from Kirill Shutemov:
 "Here's relatively low-risk part of 5-level paging patchset. Merging it
  now will make x86 5-level paging enabling in v4.12 easier.

  The first patch is actually x86-specific: detect 5-level paging
  support. It boils down to single define.

  The rest of patchset converts Linux MMU abstraction from 4- to 5-level
  paging.

  Enabling of new abstraction in most cases requires adding single line
  of code in arch-specific code. The rest is taken care by asm-generic/.

  Changes to mm/ code are mostly mechanical: add support for new page
  table level -- p4d_t -- where we deal with pud_t now.

  v2:
   - fix build on microblaze (Michal);
   - comment for __ARCH_HAS_5LEVEL_HACK in kasan_populate_zero_shadow();
   - acks from Michal"

* emailed patches from Kirill A Shutemov <kirill.shutemov@linux.intel.com>:
  mm: introduce __p4d_alloc()
  mm: convert generic code to 5-level paging
  asm-generic: introduce <asm-generic/pgtable-nop4d.h>
  arch, mm: convert all architectures to use 5level-fixup.h
  asm-generic: introduce __ARCH_USE_5LEVEL_HACK
  asm-generic: introduce 5level-fixup.h
  x86/cpufeature: Add 5-level paging detection

Merge fixes from Andrew Morton:
 "26 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (26 commits)
  userfaultfd: remove wrong comment from userfaultfd_ctx_get()
  fat: fix using uninitialized fields of fat_inode/fsinfo_inode
  sh: cayman: IDE support fix
  kasan: fix races in quarantine_remove_cache()
  kasan: resched in quarantine_remove_cache()
  mm: do not call mem_cgroup_free() from within mem_cgroup_alloc()
  thp: fix another corner case of munlock() vs. THPs
  rmap: fix NULL-pointer dereference on THP munlocking
  mm/memblock.c: fix memblock_next_valid_pfn()
  userfaultfd: selftest: vm: allow to build in vm/ directory
  userfaultfd: non-cooperative: userfaultfd_remove revalidate vma in MADV_DONTNEED
  userfaultfd: non-cooperative: fix fork fctx->new memleak
  mm/cgroup: avoid panic when init with low memory
  drivers/md/bcache/util.h: remove duplicate inclusion of blkdev.h
  mm/vmstats: add thp_split_pud event for clarity
  include/linux/fs.h: fix unsigned enum warning with gcc-4.2
  userfaultfd: non-cooperative: release all ctx in dup_userfaultfd_complete
  userfaultfd: non-cooperative: robustness check
  userfaultfd: non-cooperative: rollback userfaultfd_exit
  x86, mm: unify exit paths in gup_pte_range()
  ...

Pull xfs fixes from Darrick Wong:
 "Here are some bug fixes for -rc2 to clean up the copy on write
  handling and to remove a cause of hangs.

   - Fix various iomap bugs

   - Fix overly aggressive CoW preallocation garbage collection

   - Fixes to CoW endio error handling

   - Fix some incorrect geometry calculations

   - Remove a potential system hang in bulkstat

   - Try to allocate blocks more aggressively to reduce ENOSPC errors"

* tag 'xfs-4.11-fixes-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: try any AG when allocating the first btree block when reflinking
  xfs: use iomap new flag for newly allocated delalloc blocks
  xfs: remove kmem_zalloc_greedy
  xfs: Use xfs_icluster_size_fsb() to calculate inode alignment mask
  xfs: fix and streamline error handling in xfs_end_io
  xfs: only reclaim unwritten COW extents periodically
  iomap: invalidate page caches should be after iomap_dio_complete() in direct write

Pull gcc-plugins fix from Kees Cook:
 "Fixes a typo in sancov plugin, exposed in earlier compiler versions"

* tag 'gcc-plugins-v4.11-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  gcc-plugins: fix sancov_plugin for gcc-5

Currently when the 'power-supply' regulator is passed via device tree
it does not actually work since drm_panel_prepare()/drm_panel_enable()
are never called.

Quoting Thierry Reding: "It should really call drm_panel_prepare() and
drm_panel_enable() while switching on the display pipeline and
drm_panel_disable(), followed by drm_panel_unprepare() while switching
off the display pipeline."

So do as suggested, so that the 'power-supply' regulator can be functional.
Reported-by: Breno Lima <breno.lima@nxp.com>
Suggested-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Marek Vasut <marex@denx.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

Currently the framebuffer content is displayed with incorrect offsets
in both the vertical and horizontal directions.

The fbdev version of the driver does not show this problem. Breno Lima
dumped the eLCDIF controller registers on both the drm and fbdev drivers
and noticed that the VDCTRL3 register is configured incorrectly in the
drm driver.

The fbdev driver calculates the vertical and horizontal wait counts
of the VDCTRL3 register by doing: back porch + sync length.

Looking at the horizontal and vertical timing diagram from
include/drm/drm_modes.h this value corresponds to:

crtc_[hv]total - crtc_[hv]sync_start

So fix the VDCTRL3 register setting accordingly so that the eLCDIF
controller can properly show the framebuffer content in the correct
position.
Reported-by: Breno Lima <breno.lima@nxp.com>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Breno Lima <breno.lima@nxp.com>
Tested-by: Marek Vasut <marex@denx.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

The mxsfb driver will crash if the mxsfb DT node has a subnode,
but the content of the subnode is not of-graph binding with an
endpoint linking to panel. The crash was triggered by providing
old-style panel bindings to the mxsfb driver instead of the new
of-graph ones.

The problem happens in mxsfb_create_output(), which is invoked
from mxsfb_load(). The mxsfb_create_output() iterates over all
mxsfb DT subnode endpoints and tries to bind a panel on each
endpoint. If there is any problem binding the panel, that is,
mxsfb->panel == NULL, this function will return an error code,
otherwise success 0 is returned.

If the subnodes do not specify of-graph binding with an endpoint,
the iteration over endpoints in mxsfb_create_output() will have
zero cycles and the function will immediatelly return 0, but the
mxsfb->panel will remain NULL. This is propagated back into the
mxsfb_load(), which does not detect any problem and expects that
the mxsfb->panel is valid, thus calls mxsfb_panel_attach(). But
since mxsfb->panel == NULL, mxsfb_panel_attach() is called with
first argument NULL and this crashes the kernel.

This patch fixes the problem by explicitly checking for valid
mxsfb->panel at the end of the iteration in mxsfb_create_output().
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Breno Matheus Lima <brenomatheus@gmail.com>
Tested-by: Breno Lima <breno.lima@nxp.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

The DRM subsystem specifies the pixel clock polarity from a
controllers perspective: DRM_BUS_FLAG_PIXDATA_NEGEDGE means
the controller drives the data on pixel clocks falling edge.
That is the controllers DOTCLK_POL=0 (Default is data launched
at negative edge).

Also change the data enable logic to be high active by default
and only change if explicitly requested via bus_flags. With
that defaults are:
- Data enable: high active
- Pixel clock polarity: controller drives data on negative edge
Signed-off-by: Stefan Agner <stefan@agner.ch>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

The LCD bus width does not need to align with the pixel format. The
LCDIF controller automatically converts between pixel formats and
bus width by padding or dropping LSBs.

The DRM subsystem has the notion of bus_format which allows to
determine what bus_formats are supported by the display. Choose the
first available or fallback to 24 bit if none are available.
Signed-off-by: Stefan Agner <stefan@agner.ch>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

* 'drm-fixes-4.11' of git://people.freedesktop.org/~agd5f/linux:
  drm/amdgpu: bump driver version for some new features
  drm/amdgpu: validate paramaters in the gem ioctl
  drm/amd/amdgpu: fix console deadlock if late init failed

Merge tag 'drm-intel-fixes-2017-03-09' of git://anongit.freedesktop.org/git/drm-intel into drm-fixes

flushing out gvt-g fixes

* tag 'drm-intel-fixes-2017-03-09' of git://anongit.freedesktop.org/git/drm-intel: (29 commits)
  drm/i915/gvt: change some gvt_err to gvt_dbg_cmd
  drm/i915/gvt: protect RO and Rsvd bits of virtual vgpu configuration space
  drm/i915/gvt: handle workload lifecycle properly
  drm/i915/gvt: fix an error for F_RO flag
  drm/i915/gvt: use pfn_valid for better checking
  drm/i915/gvt: set SFUSE_STRAP properly for vitual monitor detection
  drm/i915/gvt: fix an error for one register
  drm/i915/gvt: add more registers into handlers list
  drm/i915/gvt: have more registers with F_CMD_ACCESS flags set
  drm/i915/gvt: add some new MMIOs to cmd_access white list
  drm/i915/gvt: fix pcode mailbox write emulation of BDW
  drm/i915/gvt: add resolution definition for vGPU type
  drm/i915/gvt: Add more edid definition support
  drm/i915/gvt: adjust to fixed vGPU types
  drm/i915/gvt: remove unnecessary error msg from gtt write
  drm/i915/gvt: refine pcode write emulation
  drm/i915/gvt: clear the vGPU reset logic
  drm/i915/gvt: decrease priority of output msg for untracked mmio
  drm/i915/gvt: set default value to 0 for unhandled mmio regs
  drm/i915/gvt: add cmd_access to GEN7_HALF_SLICE_CHICKEN1
  ...

Just 1 8bpc quirk from Ville, cc: stable

* tag 'drm-misc-fixes-2017-03-06' of git://anongit.freedesktop.org/git/drm-misc:
  drm/edid: Add EDID_QUIRK_FORCE_8BPC quirk for Rotel RSX-1058

It's a void function, so there is no return value;

Link: http://lkml.kernel.org/r/20170309150817.7510-1-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Recently fallocate patch was merged and it uses
MSDOS_I(inode)->mmu_private at fat_evict_inode().  However,
fat_inode/fsinfo_inode that was introduced in past didn't initialize
MSDOS_I(inode) properly.

With those combinations, it became the cause of accessing random entry
in FAT area.

Link: http://lkml.kernel.org/r/87pohrj4i8.fsf@mail.parknet.co.jpSigned-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Reported-by: Moreno Bartalucci <moreno.bartalucci@tecnorama.it>
Tested-by: Moreno Bartalucci <moreno.bartalucci@tecnorama.it>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Remove incorrect CONFIG_IDE ifdef (CONFIG_IDE config option is for
internal drivers/ide/ use) and make IDE hardware interface always
initialized (not only when IDE subsystem is built-in).

This patch allows Cayman board to work with modular IDE subsystem
support and removes the requirement of having the whole core IDE
subsystem built-in when using libata PATA support.

Link: http://lkml.kernel.org/r/1990884.yFoE6lSB9G@amdc3058Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

quarantine_remove_cache() frees all pending objects that belong to the
cache, before we destroy the cache itself.  However there are currently
two possibilities how it can fail to do so.

First, another thread can hold some of the objects from the cache in
temp list in quarantine_put().  quarantine_put() has a windows of
enabled interrupts, and on_each_cpu() in quarantine_remove_cache() can
finish right in that window.  These objects will be later freed into the
destroyed cache.

Then, quarantine_reduce() has the same problem.  It grabs a batch of
objects from the global quarantine, then unlocks quarantine_lock and
then frees the batch.  quarantine_remove_cache() can finish while some
objects from the cache are still in the local to_free list in
quarantine_reduce().

Fix the race with quarantine_put() by disabling interrupts for the whole
duration of quarantine_put().  In combination with on_each_cpu() in
quarantine_remove_cache() it ensures that quarantine_remove_cache()
either sees the objects in the per-cpu list or in the global list.

Fix the race with quarantine_reduce() by protecting quarantine_reduce()
with srcu critical section and then doing synchronize_srcu() at the end
of quarantine_remove_cache().

I've done some assessment of how good synchronize_srcu() works in this
case.  And on a 4 CPU VM I see that it blocks waiting for pending read
critical sections in about 2-3% of cases.  Which looks good to me.

I suspect that these races are the root cause of some GPFs that I
episodically hit.  Previously I did not have any explanation for them.

  BUG: unable to handle kernel NULL pointer dereference at 00000000000000c8
  IP: qlist_free_all+0x2e/0xc0 mm/kasan/quarantine.c:155
  PGD 6aeea067
  PUD 60ed7067
  PMD 0
  Oops: 0000 [#1] SMP KASAN
  Dumping ftrace buffer:
     (ftrace buffer empty)
  Modules linked in:
  CPU: 0 PID: 13667 Comm: syz-executor2 Not tainted 4.10.0+ #60
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  task: ffff88005f948040 task.stack: ffff880069818000
  RIP: 0010:qlist_free_all+0x2e/0xc0 mm/kasan/quarantine.c:155
  RSP: 0018:ffff88006981f298 EFLAGS: 00010246
  RAX: ffffea0000ffff00 RBX: 0000000000000000 RCX: ffffea0000ffff1f
  RDX: 0000000000000000 RSI: ffff88003fffc3e0 RDI: 0000000000000000
  RBP: ffff88006981f2c0 R08: ffff88002fed7bd8 R09: 00000001001f000d
  R10: 00000000001f000d R11: ffff88006981f000 R12: ffff88003fffc3e0
  R13: ffff88006981f2d0 R14: ffffffff81877fae R15: 0000000080000000
  FS:  00007fb911a2d700(0000) GS:ffff88003ec00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00000000000000c8 CR3: 0000000060ed6000 CR4: 00000000000006f0
  Call Trace:
   quarantine_reduce+0x10e/0x120 mm/kasan/quarantine.c:239
   kasan_kmalloc+0xca/0xe0 mm/kasan/kasan.c:590
   kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:544
   slab_post_alloc_hook mm/slab.h:456 [inline]
   slab_alloc_node mm/slub.c:2718 [inline]
   kmem_cache_alloc_node+0x1d3/0x280 mm/slub.c:2754
   __alloc_skb+0x10f/0x770 net/core/skbuff.c:219
   alloc_skb include/linux/skbuff.h:932 [inline]
   _sctp_make_chunk+0x3b/0x260 net/sctp/sm_make_chunk.c:1388
   sctp_make_data net/sctp/sm_make_chunk.c:1420 [inline]
   sctp_make_datafrag_empty+0x208/0x360 net/sctp/sm_make_chunk.c:746
   sctp_datamsg_from_user+0x7e8/0x11d0 net/sctp/chunk.c:266
   sctp_sendmsg+0x2611/0x3970 net/sctp/socket.c:1962
   inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:761
   sock_sendmsg_nosec net/socket.c:633 [inline]
   sock_sendmsg+0xca/0x110 net/socket.c:643
   SYSC_sendto+0x660/0x810 net/socket.c:1685
   SyS_sendto+0x40/0x50 net/socket.c:1653

I am not sure about backporting.  The bug is quite hard to trigger, I've
seen it few times during our massive continuous testing (however, it
could be cause of some other episodic stray crashes as it leads to
memory corruption...).  If it is triggered, the consequences are very
bad -- almost definite bad memory corruption.  The fix is non trivial
and has chances of introducing new bugs.  I am also not sure how
actively people use KASAN on older releases.

[dvyukov@google.com: - sorted includes[
  Link: http://lkml.kernel.org/r/20170309094028.51088-1-dvyukov@google.com
Link: http://lkml.kernel.org/r/20170308151532.5070-1-dvyukov@google.comSigned-off-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We see reported stalls/lockups in quarantine_remove_cache() on machines
with large amounts of RAM.  quarantine_remove_cache() needs to scan
whole quarantine in order to take out all objects belonging to the
cache.  Quarantine is currently 1/32-th of RAM, e.g.  on a machine with
256GB of memory that will be 8GB.  Moreover quarantine scanning is a
walk over uncached linked list, which is slow.

Add cond_resched() after scanning of each non-empty batch of objects.
Batches are specifically kept of reasonable size for quarantine_put().
On a machine with 256GB of RAM we should have ~512 non-empty batches,
each with 16MB of objects.

Link: http://lkml.kernel.org/r/20170308154239.25440-1-dvyukov@google.comSigned-off-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mem_cgroup_free() indirectly calls wb_domain_exit() which is not
prepared to deal with a struct wb_domain object that hasn't executed
wb_domain_init().  For instance, the following warning message is
printed by lockdep if alloc_percpu() fails in mem_cgroup_alloc():

  INFO: trying to register non-static key.
  the code is fine but needs lockdep annotation.
  turning off the locking correctness validator.
  CPU: 1 PID: 1950 Comm: mkdir Not tainted 4.10.0+ #151
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Call Trace:
   dump_stack+0x67/0x99
   register_lock_class+0x36d/0x540
   __lock_acquire+0x7f/0x1a30
   lock_acquire+0xcc/0x200
   del_timer_sync+0x3c/0xc0
   wb_domain_exit+0x14/0x20
   mem_cgroup_free+0x14/0x40
   mem_cgroup_css_alloc+0x3f9/0x620
   cgroup_apply_control_enable+0x190/0x390
   cgroup_mkdir+0x290/0x3d0
   kernfs_iop_mkdir+0x58/0x80
   vfs_mkdir+0x10e/0x1a0
   SyS_mkdirat+0xa8/0xd0
   SyS_mkdir+0x14/0x20
   entry_SYSCALL_64_fastpath+0x18/0xad

Add __mem_cgroup_free() which skips wb_domain_exit().  This is used by
both mem_cgroup_free() and mem_cgroup_alloc() clean up.

Fixes: 0b8f73e1 ("mm: memcontrol: clean up alloc, online, offline, free functions")
Link: http://lkml.kernel.org/r/20170306192122.24262-1-tahsin@google.comSigned-off-by: Tahsin Erdogan <tahsin@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The following test case triggers BUG() in munlock_vma_pages_range():

	int main(int argc, char *argv[])
	{
		int fd;

		system("mount -t tmpfs -o huge=always none /mnt");
		fd = open("/mnt/test", O_CREAT | O_RDWR);
		ftruncate(fd, 4UL << 20);
		mmap(NULL, 4UL << 20, PROT_READ | PROT_WRITE,
				MAP_SHARED | MAP_FIXED | MAP_LOCKED, fd, 0);
		mmap(NULL, 4096, PROT_READ | PROT_WRITE,
				MAP_SHARED | MAP_LOCKED, fd, 0);
		munlockall();
		return 0;
	}

The second mmap() create PTE-mapping of the first huge page in file.  It
makes kernel munlock the page as we never keep PTE-mapped page mlocked.

On munlockall() when we handle vma created by the first mmap(),
munlock_vma_page() returns page_mask == 0, as the page is not mlocked
anymore.  On next iteration follow_page_mask() return tail page, but
page_mask is HPAGE_NR_PAGES - 1.  It makes us skip to the first tail
page of the next huge page and step on
VM_BUG_ON_PAGE(PageMlocked(page)).

The fix is not use the page_mask from follow_page_mask() at all.  It has
no use for us.

Link: http://lkml.kernel.org/r/20170302150252.34120-1-kirill.shutemov@linux.intel.comSigned-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>    [4.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The following test case triggers NULL-pointer derefernce in
try_to_unmap_one():

	#include <fcntl.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <sys/mman.h>

	int main(int argc, char *argv[])
	{
		int fd;

		system("mount -t tmpfs -o huge=always none /mnt");
		fd = open("/mnt/test", O_CREAT | O_RDWR);
		ftruncate(fd, 2UL << 20);
		mmap(NULL, 2UL << 20, PROT_READ | PROT_WRITE,
				MAP_SHARED | MAP_FIXED | MAP_LOCKED, fd, 0);
		mmap(NULL, 2UL << 20, PROT_READ | PROT_WRITE,
				MAP_SHARED | MAP_LOCKED, fd, 0);
		munlockall();
		return 0;
	}

Apparently, there's a case when we call try_to_unmap() on huge PMDs:
it's TTU_MUNLOCK.

Let's handle this case correctly.

Fixes: c7ab0d2f ("mm: convert try_to_unmap_one() to use page_vma_mapped_walk()")
Link: http://lkml.kernel.org/r/20170302151159.30592-1-kirill.shutemov@linux.intel.comSigned-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Obviously, we should not access memblock.memory.regions[right] if
'right' is outside of [0..memblock.memory.cnt>.

Fixes: b92df1de ("mm: page_alloc: skip over regions of invalid pfns where possible")
Link: http://lkml.kernel.org/r/20170303023745.9104-1-takahiro.akashi@linaro.orgSigned-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

linux/tools/testing/selftests/vm $ make

  gcc -Wall -I ../../../../usr/include     compaction_test.c -lrt -o /compaction_test
  /usr/lib/gcc/x86_64-pc-linux-gnu/4.9.4/../../../../x86_64-pc-linux-gnu/bin/ld: cannot open output file /compaction_test: Permission denied
  collect2: error: ld returned 1 exit status
  make: *** [../lib.mk:54: /compaction_test] Error 1

Since commit a8ba798b ("selftests: enable O and KBUILD_OUTPUT")
selftests/vm build fails if run from the "selftests/vm" directory, but
it works in the selftests/ directory.  It's quicker to be able to do a
local vm-only build after a tree wipe and this patch allows for it
again.

Link: http://lkml.kernel.org/r/20170302173738.18994-4-aarcange@redhat.comSigned-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

userfaultfd_remove() has to be execute before zapping the pagetables or
UFFDIO_COPY could keep filling pages after zap_page_range returned,
which would result in non zero data after a MADV_DONTNEED.

However userfaultfd_remove() may have to release the mmap_sem.  This was
handled correctly in MADV_REMOVE, but MADV_DONTNEED accessed a
potentially stale vma (the very vma passed to zap_page_range(vma, ...)).

The fix consists in revalidating the vma in case userfaultfd_remove()
had to release the mmap_sem.

This also optimizes away an unnecessary down_read/up_read in the
MADV_REMOVE case if UFFD_EVENT_FORK had to be delivered.

It all remains zero runtime cost in case CONFIG_USERFAULTFD=n as
userfaultfd_remove() will be defined as "true" at build time.

Link: http://lkml.kernel.org/r/20170302173738.18994-3-aarcange@redhat.comSigned-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>