Pull btrfs fixes from Chris Mason:
 "We've had a busy two weeks of bug fixing.  The biggest patches in here
  are some long standing early-enospc problems (Josef) and a very old
  race where compression and mmap combine forces to lose writes (me).
  I'm fairly sure the mmap bug goes all the way back to the introduction
  of the compression code, which is proof that fsx doesn't trigger every
  possible mmap corner after all.

  I'm sure you'll notice one of these is from this morning, it's a small
  and isolated use-after-free fix in our scrub error reporting.  I
  double checked it here."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  Btrfs: don't drop path when printing out tree errors in scrub
  Btrfs: fix wrong return value of btrfs_lookup_csum()
  Btrfs: fix wrong reservation of csums
  Btrfs: fix double free in the btrfs_qgroup_account_ref()
  Btrfs: limit the global reserve to 512mb
  Btrfs: hold the ordered operations mutex when waiting on ordered extents
  Btrfs: fix space accounting for unlink and rename
  Btrfs: fix space leak when we fail to reserve metadata space
  Btrfs: fix EIO from btrfs send in is_extent_unchanged for punched holes
  Btrfs: fix race between mmap writes and compression
  Btrfs: fix memory leak in btrfs_create_tree()
  Btrfs: fix locking on ROOT_REPLACE operations in tree mod log
  Btrfs: fix missing qgroup reservation before fallocating
  Btrfs: handle a bogus chunk tree nicely
  Btrfs: update to use fs_state bit

Commit 3e7fc708 ("ia64 idle: delete pm_idle") in 3.9-rc1 didn't
finish the job, leaving an un-initialized reference to (*idle)().

[ Haven't seen a crash from this - but seems like we are just being
  lucky that "idle" is zero so it does get initialized before we jump to
  randomland  - Len ]
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull arc architecture fixes from Vineet Gupta:
 "This includes fix for a serious bug in DMA mapping API, make
  allyesconfig wreckage, removal of bogus email-list placeholder in
  MAINTAINERS, a typo in ptrace helper code and last remaining changes
  for syscall ABI v3 which we are finally starting to transition-to
  internally.

  The request is late than I intended to - but I was held up with
  debugging a timer link list corruption, for which a proposed fix to
  generic timer code was sent out to lkml/tglx earlier today."

* 'for-curr' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: Fix the typo in event identifier flags used by ptrace
  arc: fix dma_address assignment during dma_map_sg()
  ARC: Remove SET_PERSONALITY (tracks cross-arch change)
  ARC: ABIv3: fork/vfork wrappers not needed in "no-legacy-syscall" ABI
  ARC: ABIv3: Print the correct ABI ver
  ARC: make allyesconfig build breakages
  ARC: MAINTAINERS update for ARC

A user reported a panic where we were panicing somewhere in
tree_backref_for_extent from scrub_print_warning.  He only captured the trace
but looking at scrub_print_warning we drop the path right before we mess with
the extent buffer to print out a bunch of stuff, which isn't right.  So fix this
by dropping the path after we use the eb if we need to.  Thanks,

Cc: stable@vger.kernel.org
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

This reverts commit 18693050 ("mm: introduce VM_POPULATE flag to
better deal with racy userspace programs").

VM_POPULATE only has any effect when userspace plays racy games with
vmas by trying to unmap and remap memory regions that mmap or mlock are
operating on.

Also, the only effect of VM_POPULATE when userspace plays such games is
that it avoids populating new memory regions that get remapped into the
address range that was being operated on by the original mmap or mlock
calls.

Let's remove VM_POPULATE as there isn't any strong argument to mandate a
new vm_flag.
Signed-off-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull USB fixes from Greg Kroah-Hartman:
 "Here are some USB fixes to resolve issues reported recently, as well
  as a new device id for the ftdi_sio driver."

* tag 'usb-3.9-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  usb: ftdi_sio: Add support for Mitsubishi FX-USB-AW/-BD
  usb: Fix compile error by selecting USB_OTG_UTILS
  USB: serial: fix hang when opening port
  USB: EHCI: fix bug in iTD/siTD DMA pool allocation
  xhci: Don't warn on empty ring for suspended devices.
  usb: xhci: Fix TRB transfer length macro used for Event TRB.
  usb/acpi: binding xhci root hub usb port with ACPI
  usb: add find_raw_port_number callback to struct hc_driver()
  usb: xhci: fix build warning

Pull TTY/serial fixes from Greg Kroah-Hartman:
 "Here are some tty/serial driver fixes for 3.9.

  The big thing here is the fix for the huge mess we caused renaming the
  8250 driver accidentally in the 3.7 kernel release, without realizing
  that there were users of the module options that suddenly broke.  This
  is now resolved, and, to top the injury off, we have a backwards-
  compatible option for those users who got used to the new name since
  3.7.  Ugh, sorry about that.

  Other than that, some other minor fixes for issues that have been
  reported by users."

* tag 'tty-3.9-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  Xilinx: ARM: UART: clear pending irqs before enabling irqs
  TTY: 8250, deprecated 8250_core.* options
  TTY: 8250, revert module name change
  serial: 8250_pci: Add WCH CH352 quirk to avoid Xscale detection
  tty: atmel_serial_probe(): index of atmel_ports[] fix

Pull staging driver fixes from Greg Kroah-Hartman:
 "Here are two tiny staging driver fixes to resolve issues that have
  been reported."

* tag 'staging-3.9-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  staging: comedi: s626: fix continuous acquisition
  staging: zcache: fix typo "64_BIT"

Pull sysfs fixes from Greg Kroah-Hartman:
 "Here are two fixes for sysfs that resolve issues that have been found
  by the Trinity fuzz tool, causing oopses in sysfs.  They both have
  been in linux-next for a while to ensure that they do not cause any
  other problems."

* tag 'driver-core-3.9-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  sysfs: handle failure path correctly for readdir()
  sysfs: fix race between readdir and lseek

Pull char/misc driver fixes from Greg Kroah-Hartman:
 "Here are some small char/misc driver fixes that resolve issues
  recently reported against the 3.9-rc kernels.  All have been in
  linux-next for a while."

* tag 'char-misc-3.9-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  VMCI: Fix process-to-process DRGAMs.
  mei: ME hardware reset needs to be synchronized
  mei: add mei_stop function to stop mei device
  extcon: max77693: Initialize register of MUIC device to bring up it without platform data
  extcon: max77693: Fix bug of wrong pointer when platform data is not used
  extcon: max8997: Check the pointer of platform data to protect null pointer error

Pull ACPI and power management fixes from Rafael J Wysocki:

 - Fix for a recent cpufreq regression related to acpi-cpufreq and
   suspend/resume from Viresh Kumar.

 - cpufreq stats reference counting fix from Viresh Kumar.

 - intel_pstate driver fixes from Dirk Brandewie and Konrad Rzeszutek
   Wilk.

 - New ACPI suspend blacklist entry for Sony Vaio VGN-FW21M from Fabio
   Valentini.

 - ACPI Platform Error Interface (APEI) fix from Chen Gong.

 - PCI root bridge hotplug locking fix from Yinghai Lu.

* tag 'pm+acpi-3.9-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  PCI / ACPI: hold acpi_scan_lock during root bus hotplug
  ACPI / APEI: fix error status check condition for CPER
  ACPI / PM: fix suspend and resume on Sony Vaio VGN-FW21M
  cpufreq: acpi-cpufreq: Don't set policy->related_cpus from .init()
  cpufreq: stats: do cpufreq_cpu_put() corresponding to cpufreq_cpu_get()
  intel-pstate: Use #defines instead of hard-coded values.
  cpufreq / intel_pstate: Fix calculation of current frequency
  cpufreq / intel_pstate: Add function to check that all MSRs are valid

Pull crypto fixes from Herbert Xu:
 "This removes IPsec ESN support from the talitos/caam drivers since
  they were implemented incorrectly, causing interoperability problems
  if ESN is used with them."

* git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
  Revert "crypto: caam - add IPsec ESN support"
  Revert "crypto: talitos - add IPsec ESN support"

Pull arm64 fix from Catalin Marinas:
 "Fix IS_ENABLED() usage typo (missing CONFIG_ prefix)."

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux-aarch64:
  ARM64: early_printk: Fix check for CONFIG_ARM64_64K_PAGES

Pull fbdev fixes from Tomi Valkeinen:
 "Since Florian is still away/inactive, I volunteered to collect fbdev
  fixes for 3.9 and changes for 3.10.  I didn't receive any other fbdev
  fixes than OMAP yet, but I didn't want to delay this further as
  there's a compilation fix for OMAP1.  So there could be still some
  fbdev fixes on the way a bit later.

  This contains:

   - Fix OMAP1 compilation
   - OMAP display fixes"

* tag 'fbdev-fixes-3.9-rc4' of git://gitorious.org/linux-omap-dss2/linux:
  omapdss: features: fix supported outputs for OMAP4
  OMAPDSS: tpo-td043 panel: fix data passing between SPI/DSS parts
  omapfb: fix broken build on OMAP1

Pull userns fixes from Eric W Biederman:
 "The bulk of the changes are fixing the worst consequences of the user
  namespace design oversight in not considering what happens when one
  namespace starts off as a clone of another namespace, as happens with
  the mount namespace.

  The rest of the changes are just plain bug fixes.

  Many thanks to Andy Lutomirski for pointing out many of these issues."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  userns: Restrict when proc and sysfs can be mounted
  ipc: Restrict mounting the mqueue filesystem
  vfs: Carefully propogate mounts across user namespaces
  vfs: Add a mount flag to lock read only bind mounts
  userns:  Don't allow creation if the user is chrooted
  yama:  Better permission check for ptraceme
  pid: Handle the exit of a multi-threaded init.
  scm: Require CAP_SYS_ADMIN over the current pidns to spoof pids.

It enhances the driver for FTDI-based USB serial adapters
to recognize Mitsubishi Electric Corp. USB/RS422 Converters
as FT232BM chips and support them.
https://search.meau.com/?q=FX-USB-AWSigned-off-by: Konstantin Holoborodko <klh.kernel@gmail.com>
Tested-by: Konstantin Holoborodko <klh.kernel@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

If we don't find the expected csum item, but find a csum item which is
adjacent to the specified extent, we should return -EFBIG, or we should
return -ENOENT. But btrfs_lookup_csum() return -EFBIG even the csum item
is not adjacent to the specified extent. Fix it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

We reserve the space for csums only when we write data into a file, in
the other cases, such as tree log, log replay, we don't do reservation,
so we can use the reservation of the transaction handle just for the former.
And for the latter, we should use the tree's own reservation. But the
function - btrfs_csum_file_blocks() didn't differentiate between these
two types of the cases, fix it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

The function btrfs_find_all_roots is responsible to allocate
memory for 'roots' and free it if errors happen,so the caller should not
free it again since the work has been done.

Besides,'tmp' is allocated after the function btrfs_find_all_roots,
so we can return directly if btrfs_find_all_roots() fails.
Signed-off-by: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

A user reported a problem where he was getting early ENOSPC with hundreds of
gigs of free data space and 6 gigs of free metadata space.  This is because the
global block reserve was taking up the entire free metadata space.  This is
ridiculous, we have infrastructure in place to throttle if we start using too
much of the global reserve, so instead of letting it get this huge just limit it
to 512mb so that users can still get work done.  This allowed the user to
complete his rsync without issues.  Thanks

Cc: stable@vger.kernel.org
Reported-and-tested-by: Stefan Priebe <s.priebe@profihost.ag>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

We need to hold the ordered_operations mutex while waiting on ordered extents
since we splice and run the ordered extents list.  We need to make sure anybody
else who wants to wait on ordered extents does actually wait for them to be
completed.  This will keep us from bailing out of flushing in case somebody is
already waiting on ordered extents to complete.  Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

We are way over-reserving for unlink and rename.  Rename is just some random
huge number and unlink accounts for tree log operations that don't actually
happen during unlink, not to mention the tree log doesn't take from the trans
block rsv anyway so it's completely useless.  Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

Dave reported a warning when running xfstest 275.  We have been leaking delalloc
metadata space when our reservations fail.  This is because we were improperly
calculating how much space to free for our checksum reservations.  The problem
is we would sometimes free up space that had already been freed in another
thread and we would end up with negative usage for the delalloc space.  This
patch fixes the problem by calculating how much space the other threads would
have already freed, and then calculate how much space we need to free had we not
done the reservation at all, and then freeing any excess space.  This makes
xfstests 275 no longer have leaked space.  Thanks

Cc: stable@vger.kernel.org
Reported-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

When you take a snapshot, punch a hole where there has been data, then take
another snapshot and try to send an incremental stream, btrfs send would
give you EIO. That is because is_extent_unchanged had no support for holes
being punched. With this patch, instead of returning EIO we just return
0 (== the extent is not unchanged) and we're good.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Cc: Alexander Block <ablock84@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

* acpi-fixes:
  PCI / ACPI: hold acpi_scan_lock during root bus hotplug
  ACPI / APEI: fix error status check condition for CPER
  ACPI / PM: fix suspend and resume on Sony Vaio VGN-FW21M

* pm-fixes:
  cpufreq: acpi-cpufreq: Don't set policy->related_cpus from .init()
  cpufreq: stats: do cpufreq_cpu_put() corresponding to cpufreq_cpu_get()
  intel-pstate: Use #defines instead of hard-coded values.
  cpufreq / intel_pstate: Fix calculation of current frequency
  cpufreq / intel_pstate: Add function to check that all MSRs are valid

Pull powerpc build fixes from Stephen Rothwell:
 "Just a couple of build fixes for powerpc all{mod,yes}config.

  Submitted by me since BenH is on vacation."

* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sfr/next-fixes:
  powerpc: define the conditions where the ePAPR idle hcall can be supported
  powerpc: make additional room in exception vector area

Merge tag 'stable/for-linus-3.9-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen

Pull Xen bug-fixes from Konrad Rzeszutek Wilk:
 "This is mostly just the last stragglers of the regression bugs that
  this merge window had.  There are also two bug-fixes: one that adds an
  extra layer of security, and a regression fix for a change that was
  added in v3.7 (the v1 was faulty, the v2 works).

   - Regression fixes for C-and-P states not being parsed properly.
   - Fix possible security issue with guests triggering DoS via
     non-assigned MSI-Xs.
   - Fix regression (introduced in v3.7) with raising an event (v2).
   - Fix hastily introduced band-aid during c0 for the CR3 blowup."

* tag 'stable/for-linus-3.9-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen/events: avoid race with raising an event in unmask_evtchn()
  xen/mmu: Move the setting of pvops.write_cr3 to later phase in bootup.
  xen/acpi-stub: Disable it b/c the acpi_processor_add is no longer called.
  xen-pciback: notify hypervisor about devices intended to be assigned to guests
  xen/acpi-processor: Don't dereference struct acpi_processor on all CPUs.

Pull HID fixes from Jiri Kosina:

 - fix for potential 3.9 regression in handling of buttons for touchpads
   following HID mt specification; potential because reportedly there is
   no retail product on the market that would be using this feature, but
   nevertheless we'd better follow the spec.  Fix by Benjamin Tissoires.

 - support for two quirky devices added by Josh Boyer.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid:
  HID: multitouch: fix touchpad buttons
  HID: usbhid: fix build problem
  HID: usbhid: quirk for MSI GX680R led panel
  HID: usbhid: quirk for Realtek Multi-card reader

Pull IOMMU fixes from Joerg Roedel:
 "Here are some fixes which have collected since Linux v3.9-rc1.

  The most important one fixes a long-standing regressen which make
  re-hotplugged devices unusable when AMD IOMMU is used.

  The other patches fix build issues (build regression on OMAP and a
  section mismatch).  One patch just removes a duplicate header include."

* tag 'iommu-fixes-v3.9-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu:
  iommu/amd: Make sure dma_ops are set for hotplug devices
  x86, io_apic: remove duplicated include from irq_remapping.c
  iommu: OMAP: build only on OMAP2+
  amd_iommu_init: remove __init from amd_iommu_erratum_746_workaround

Commit 06ae43f3 ("Don't bother with redoing rw_verify_area() from
default_file_splice_from()") lost the checks to test existence of the
write/aio_write methods.  My apologies ;-/

Eventually, we want that in fs/splice.c side of things (no point
repeating it for every buffer, after all), but for now this is the
obvious minimal fix.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In unmask_evtchn(), when the mask bit is cleared after testing for
pending and the event becomes pending between the test and clear, then
the upcall will not become pending and the event may be lost or
delayed.

Avoid this by always clearing the mask bit before checking for
pending.  If a hypercall is needed, remask the event as
EVTCHNOP_unmask will only retrigger pending events if they were
masked.

This fixes a regression introduced in 3.7 by
b5e57923 (xen/events: fix
unmask_evtchn for PV on HVM guests) which reordered the clear mask and
check pending operations.

Changes in v2:
- set mask before hypercall.

Cc: stable@vger.kernel.org
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

We move the setting of write_cr3 from the early bootup variant
(see git commit 0cc9129d
"x86-64, xen, mmu: Provide an early version of write_cr3.")
to a more appropiate location.

This new location sets all of the other non-early variants
of pvops calls - and most importantly is before the
alternative_asm mechanism kicks in.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

With the Xen ACPI stub code (CONFIG_XEN_STUB=y) enabled, the power
C and P states are no longer uploaded to the hypervisor.

The reason is that the Xen CPU hotplug code: xen-acpi-cpuhotplug.c
and the xen-acpi-stub.c register themselves as the "processor" type object.

That means the generic processor (processor_driver.c) stops
working and it does not call (acpi_processor_add) which populates the

         per_cpu(processors, pr->id) = pr;

structure. The 'pr' is gathered from the acpi_processor_get_info function
which does the job of finding the C-states and figuring out PBLK address.

The 'processors->pr' is then later used by xen-acpi-processor.c (the one that
uploads C and P states to the hypervisor). Since it is NULL, we end
skip the gathering of _PSD, _PSS, _PCT, etc and never upload the power
management data.

The end result is that enabling the CONFIG_XEN_STUB in the build means that
xen-acpi-processor is not working anymore.

This temporary patch fixes it by marking the XEN_STUB driver as
BROKEN until this can be properly fixed.

CC: jinsong.liu@intel.com
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The current lpc32xx_defconfig breaks like this, caused by recent phy
restructuring:

  LD      init/built-in.o
drivers/built-in.o: In function `usb_hcd_nxp_probe':
drivers/usb/host/ohci-nxp.c:224: undefined reference to `isp1301_get_client'
drivers/built-in.o: In function `lpc32xx_udc_probe':
drivers/usb/gadget/lpc32xx_udc.c:3104: undefined reference to
`isp1301_get_client' distcc[27867] ERROR: compile (null) on localhost failed
make: *** [vmlinux] Error 1

Caused by 1c208881 (usb: Makefile: fix
drivers/usb/phy/ Makefile entry)

This patch fixes this by selecting USB_OTG_UTILS in Kconfig which
causes the phy driver to be built again.
Signed-off-by: Roland Stigge <stigge@antcom.de>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Only allow unprivileged mounts of proc and sysfs if they are already
mounted when the user namespace is created.

proc and sysfs are interesting because they have content that is
per namespace, and so fresh mounts are needed when new namespaces
are created while at the same time proc and sysfs have content that
is shared between every instance.

Respect the policy of who may see the shared content of proc and sysfs
by only allowing new mounts if there was an existing mount at the time
the user namespace was created.

In practice there are only two interesting cases: proc and sysfs are
mounted at their usual places, proc and sysfs are not mounted at all
(some form of mount namespace jail).

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Only allow mounting the mqueue filesystem if the caller has CAP_SYS_ADMIN
rights over the ipc namespace.   The principle here is if you create
or have capabilities over it you can mount it, otherwise you get to live
with what other people have mounted.

This information is not particularly sensitive and mqueue essentially
only reports which posix messages queues exist.  Still when creating a
restricted environment for an application to live any extra
information may be of use to someone with sufficient creativity.  The
historical if imperfect way this information has been restricted has
been not to allow mounts and restricting this to ipc namespace
creators maintains the spirit of the historical restriction.

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

As a matter of policy MNT_READONLY should not be changable if the
original mounter had more privileges than creator of the mount
namespace.

Add the flag CL_UNPRIVILEGED to note when we are copying a mount from
a mount namespace that requires more privileges to a mount namespace
that requires fewer privileges.

When the CL_UNPRIVILEGED flag is set cause clone_mnt to set MNT_NO_REMOUNT
if any of the mnt flags that should never be changed are set.

This protects both mount propagation and the initial creation of a less
privileged mount namespace.

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

When a read-only bind mount is copied from mount namespace in a higher
privileged user namespace to a mount namespace in a lesser privileged
user namespace, it should not be possible to remove the the read-only
restriction.

Add a MNT_LOCK_READONLY mount flag to indicate that a mount must
remain read-only.

CC: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Guarantee that the policy of which files may be access that is
established by setting the root directory will not be violated
by user namespaces by verifying that the root directory points
to the root of the mount namespace at the time of user namespace
creation.

Changing the root is a privileged operation, and as a matter of policy
it serves to limit unprivileged processes to files below the current
root directory.

For reasons of simplicity and comprehensibility the privilege to
change the root directory is gated solely on the CAP_SYS_CHROOT
capability in the user namespace.  Therefore when creating a user
namespace we must ensure that the policy of which files may be access
can not be violated by changing the root directory.

Anyone who runs a processes in a chroot and would like to use user
namespace can setup the same view of filesystems with a mount
namespace instead.  With this result that this is not a practical
limitation for using user namespaces.

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>