In preparation for the dax implementation to start associating dax pages
to inodes via page->mapping, we need to provide a 'struct
address_space_operations' instance for dax. Otherwise, direct-I/O
triggers incorrect page cache assumptions and warnings like the
following:

 WARNING: CPU: 27 PID: 1783 at fs/xfs/xfs_aops.c:1468
 xfs_vm_set_page_dirty+0xf3/0x1b0 [xfs]
 [..]
 CPU: 27 PID: 1783 Comm: dma-collision Tainted: G           O 4.15.0-rc2+ #984
 [..]
 Call Trace:
  set_page_dirty_lock+0x40/0x60
  bio_set_pages_dirty+0x37/0x50
  iomap_dio_actor+0x2b7/0x3b0
  ? iomap_dio_zero+0x110/0x110
  iomap_apply+0xa4/0x110
  iomap_dio_rw+0x29e/0x3b0
  ? iomap_dio_zero+0x110/0x110
  ? xfs_file_dio_aio_read+0x7c/0x1a0 [xfs]
  xfs_file_dio_aio_read+0x7c/0x1a0 [xfs]
  xfs_file_read_iter+0xa0/0xc0 [xfs]
  __vfs_read+0xf9/0x170
  vfs_read+0xa6/0x150
  SyS_pread64+0x93/0xb0
  entry_SYSCALL_64_fastpath+0x1f/0x96

...where the default set_page_dirty() handler assumes that dirty state
is being tracked in 'struct page' flags.

Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Jan Kara <jack@suse.cz>
Suggested-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Block device inodes never have S_DAX set, so kill the check for DAX and
diversion to dax_writeback_mapping_range().

Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

In preparation for the dax implementation to start associating dax pages
to inodes via page->mapping, we need to provide a 'struct
address_space_operations' instance for dax. Define some generic VFS aops
helpers for dax. These noop implementations are there in the dax case to
prevent the VFS from falling back to operations with page-cache
assumptions, dax_writeback_mapping_range() may not be referenced in the
FS_DAX=n case.

Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Matthew Wilcox <mawilcox@microsoft.com>
Suggested-by: Jan Kara <jack@suse.cz>
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Suggested-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

In preparation for examining the busy state of dax pages in the truncate
path, switch from sectors to pfns in the radix.

Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

As a replacement for the wait_on_atomic_t() API provide the
wait_var_event() API.

The wait_var_event() API is based on the very same hashed-waitqueue
idea, but doesn't care about the type (atomic_t) or the specific
condition (atomic_read() == 0). IOW. it's much more widely
applicable/flexible.

It shares all the benefits/disadvantages of a hashed-waitqueue
approach with the existing wait_on_atomic_t/wait_on_bit() APIs.

The API is modeled after the existing wait_event() API, but instead of
taking a wait_queue_head, it takes an address. This addresses is
hashed to obtain a wait_queue_head from the bit_wait_table.

Similar to the wait_event() API, it takes a condition expression as
second argument and will wait until this expression becomes true.

The following are (mostly) identical replacements:

	wait_on_atomic_t(&my_atomic, atomic_t_wait, TASK_UNINTERRUPTIBLE);
	wake_up_atomic_t(&my_atomic);

	wait_var_event(&my_atomic, !atomic_read(&my_atomic));
	wake_up_var(&my_atomic);

The only difference is that wake_up_var() is an unconditional wakeup
and doesn't check the previously hard-coded (atomic_read() == 0)
condition here. This is of little concequence, since most callers are
already conditional on atomic_dec_and_test() and the ones that are
not, are trivial to make so.
Tested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Signed-off-by: Ingo Molnar <mingo@kernel.org>

Pull virtio bugfix from Michael Tsirkin:
 "A bugfix for error handling in virtio"

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
  virtio_ring: fix num_free handling in error case

Pull input fixes from Dmitry Torokhov:

 - we are reverting patch that was switched touchpad on Lenovo T460P
   over to native RMI because on these boxes BIOS messes up with SMBus
   controller state. We might re-enable it later once SMBus issue is
   resolved

 - disabling interrupts in matrix_keypad driver was racy

 - mms114 now has SPDX header and matching MODULE_LICENSE

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Revert "Input: synaptics - Lenovo Thinkpad T460p devices should use RMI"
  Input: matrix_keypad - fix race when disabling interrupts
  Input: mms114 - add SPDX identifier
  Input: mms114 - fix license module information

This reverts commit 48282969 which
caused the following issues:

1. On T460p with BIOS version 2.22 touchpad and trackpoint stop working
after suspend-resume cycle. Due to strange state of the device another
suspend is impossible.

The following dmesg errors can be observed:
thinkpad_acpi: EC reports that Thermal Table has changed
rmi4_smbus 7-002c: failed to get SMBus version number!
rmi4_physical rmi4-00: rmi_driver_reset_handler: Failed to read current IRQ mask.
rmi4_f01 rmi4-00.fn01: Failed to restore normal operation: -16.
rmi4_f01 rmi4-00.fn01: Resume failed with code -16.
rmi4_physical rmi4-00: Failed to suspend functions: -16
rmi4_smbus 7-002c: Failed to resume device: -16
PM: resume devices took 0.640 seconds
rmi4_f03 rmi4-00.fn03: rmi_f03_pt_write: Failed to write to F03 TX register (-16).
rmi4_physical rmi4-00: rmi_driver_clear_irq_bits: Failed to change enabled interrupts!
rmi4_physical rmi4-00: rmi_driver_set_irq_bits: Failed to change enabled interrupts!
psmouse: probe of serio3 failed with error -1

2. On another T460p with BIOS version 2.15 two finger scrolling gesture
on the touchpad stops working after suspend-resume cycle (about 75%
reproducibility, when it still works, the scrolling gesture becomes
laggy). Nothing suspicious appears in the dmesg.

Analysis form Richard Schütz:

"RMI is unreliable on the ThinkPad T460p because the device is affected
by the firmware behavior addressed in a7ae8195 ("i2c: i801: Allow
ACPI SystemIO OpRegion to conflict with PCI BAR")."

The affected devices often show:

i801_smbus 0000:00:1f.4: BIOS is accessing SMBus registers
i801_smbus 0000:00:1f.4: Driver SMBus register access inhibited
Reported-by: Richard Schütz <rschuetz@uni-koblenz.de>
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Tested-by: Martin Peres <martin.peres@linux.intel.com>
Tested-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Pull gfs2 fix from Bob Peterson:
 "An additional patch from Andreas Gruenbacher that fixes another
  unfortunate GFS2 regression"

* tag 'gfs2-4.16.rc4.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
  gfs2: Fixes to "Implement iomap for block_map" (2)

Pull s390 fixes from Martin Schwidefsky:
 "Nine bug fixes for s390:

   - Three fixes for the expoline code, one of them is strictly speaking
     a cleanup but as it relates to code added with 4.16 I would like to
     include the patch.

   - Three timer related fixes in the common I/O layer

   - A fix for the handling of internal DASD request which could cause
     panics.

   - One correction in regard to the accounting of pud page tables vs.
     compat tasks.

   - The register scrubbing in entry.S caused spurious crashes, this is
     fixed now as well"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/entry.S: fix spurious zeroing of r0
  s390: Fix runtime warning about negative pgtables_bytes
  s390: do not bypass BPENTER for interrupt system calls
  s390/cio: clear timer when terminating driver I/O
  s390/cio: fix return code after missing interrupt
  s390/cio: fix ccw_device_start_timeout API
  s390/clean-up: use CFI_* macros in entry.S
  s390: Replace IS_ENABLED(EXPOLINE_*) with IS_ENABLED(CONFIG_EXPOLINE_*)
  s390/dasd: fix handling of internal requests

Merge tag 'regulator-fix-v4.16-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator

Pull regulator fixes from Mark Brown:
 "A couple of fixes here:

   - another half of the supend to idle fix from Geert that went in
     earlier, both he and I are confused as to why he didn't notice that
     this was missing when his earlier fix was merged.

   - a simple fix for a test done the wrong way round in the
     stm32-vrefbuf driver"

* tag 'regulator-fix-v4.16-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator:
  regulator: Fix resume from suspend to idle
  regulator: stm32-vrefbuf: fix check on ready flag

Pull SCSI fixes from James Bottomley:
 "This is mostly fixes for driver specific issues (nine of them) and the
  storvsc performance improvement with interrupt handling which was
  dropped from the previous fixes pull request.

  We also have two regressions: one is a double call_rcu() in ATA error
  handling and the other is a missed conversion to BLK_STS_OK in
  __scsi_error_from_host_byte()"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: qedi: Fix kernel crash during port toggle
  scsi: qla2xxx: Fix FC-NVMe LUN discovery
  scsi: core: return BLK_STS_OK for DID_OK in __scsi_error_from_host_byte()
  scsi: core: Avoid that ATA error handling can trigger a kernel hang or oops
  scsi: qla2xxx: ensure async flags are reset correctly
  scsi: qla2xxx: do not check login_state if no loop id is assigned
  scsi: qla2xxx: Fixup locking for session deletion
  scsi: qla2xxx: Fix NULL pointer crash due to active timer for ABTS
  scsi: mpt3sas: wait for and flush running commands on shutdown/unload
  scsi: mpt3sas: fix oops in error handlers after shutdown/unload
  scsi: storvsc: Spread interrupts when picking a channel for I/O requests
  scsi: megaraid_sas: Do not use 32-bit atomic request descriptor for Ventura controllers

It turns out that commit 3229c18c0d6b2 'Fixes to "Implement iomap for
block_map"' introduced another bug in gfs2_iomap_begin that can cause
gfs2_block_map to set bh->b_size of an actual buffer to 0.  This can
lead to arbitrary incorrect behavior including crashes or disk
corruption.  Revert the incorrect part of that commit.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

Merge remote-tracking branches 'regulator/fix/resume' and 'regulator/fix/stm32-vfrefbuf' into regulator-linus

Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull sigingo fix from Eric Biederman:
 "The kbuild test robot found that I accidentally moved si_pkey when I
  was cleaning up siginfo_t. A short followed by an int with the int
  having 8 byte alignment. Sheesh siginfo_t is a weird structure.

  I have now corrected it and added build time checks that with a little
  luck will catch any similar future mistakes. The build time checks
  were sufficient for me to verify the bug and to verify my fix. So they
  are at least useful this once."

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  signal/x86: Include the field offsets in the build time checks
  signal: Correct the offset of si_pkey in struct siginfo

when a system call is interrupted we might call the critical section
cleanup handler that re-does some of the operations. When we are between
.Lsysc_vtime and .Lsysc_do_svc we might also redo the saving of the
problem state registers r0-r7:

.Lcleanup_system_call:
[...]
0:      # update accounting time stamp
        mvc     __LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
        # set up saved register r11
        lg      %r15,__LC_KERNEL_STACK
        la      %r9,STACK_FRAME_OVERHEAD(%r15)
        stg     %r9,24(%r11)            # r11 pt_regs pointer
        # fill pt_regs
        mvc     __PT_R8(64,%r9),__LC_SAVE_AREA_SYNC
--->    stmg    %r0,%r7,__PT_R0(%r9)

The problem is now, that we might have already zeroed out r0.
The fix is to move the zeroing of r0 after sysc_do_svc.
Reported-by: Farhan Ali <alifm@linux.vnet.ibm.com>
Fixes: 7041d281 ("s390: scrub registers on kernel entry and KVM exit")
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Due to an oversight when refactoring siginfo_t si_pkey has been in the
wrong position since 4.16-rc1.  Add an explicit check of the offset of
every user space field in siginfo_t and compat_siginfo_t to make a
mistake like this hard to make in the future.

I have run this code on 4.15 and 4.16-rc1 with the position of si_pkey
fixed and all of the fields show up in the same location.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

The change moving addr_lsb into the _sigfault union failed to take
into account that _sigfault._addr_bnd._lower being a pointer forced
the entire union to have pointer alignment.  In practice this only
mattered for the offset of si_pkey which is why this has taken so long
to discover.

To correct this change _dummy_pkey and _dummy_bnd to have pointer type.
Reported-by: kernel test robot <shun.hao@intel.com>
Fixes: b68a68d3 ("signal: Move addr_lsb into the _sigfault union for clarity")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Pull ia64 cleanups from Tony Luck:

 - More atomic cleanup from willy

 - Fix a python script to work with version 3

 - Some other small cleanups

* tag 'please-pull-ia64_misc' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux:
  ia64/err-inject: fix spelling mistake: "capapbilities" -> "capabilities"
  ia64/err-inject: Use get_user_pages_fast()
  ia64: doc: tweak whitespace for 'console=' parameter
  ia64: Convert remaining atomic operations
  ia64: convert unwcheck.py to python3

Trivial fix to spelling mistake in debug message text.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

At the point of sysfs callback, the call to gup is
done without mmap_sem (or any lock for that matter).
This is racy. As such, use the get_user_pages_fast()
alternative and safely avoid taking the lock, if possible.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>

CC: Tony Luck <tony.luck@intel.com>
CC: Fenghua Yu <fenghua.yu@intel.com>
CC: linux-ia64@vger.kernel.org
CC: linux-kernel@vger.kernel.org
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

While we've only seen inlining problems with atomic_sub_return(),
the other atomic operations could have the same problem.  Convert all
remaining operations to use the same solution as atomic_sub_return().
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

Since my system use python3 as default, arch/ia64/scripts/unwcheck.py no
longer run.

This patch convert it to the python3 syntax.
I have ran it with python2/python3 while printing values of
start/end/rlen_sum which could be impacted by this change and I see no difference.

Fixes: 94a47083 ("scripts: change scripts to use system python instead of env")
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

Merge tag 'linux-kselftest-4.16-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest

Pull kselftest fixes from Shuah Khan:
 "A fix for regression in memory-hotplug install script that prevents
  the test from running on the target"

* tag 'linux-kselftest-4.16-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
  selftests: memory-hotplug: fix emit_tests regression

Pull networking fixes from David Miller:

 1) Use an appropriate TSQ pacing shift in mac80211, from Toke
    Høiland-Jørgensen.

 2) Just like ipv4's ip_route_me_harder(), we have to use skb_to_full_sk
    in ip6_route_me_harder, from Eric Dumazet.

 3) Fix several shutdown races and similar other problems in l2tp, from
    James Chapman.

 4) Handle missing XDP flush properly in tuntap, for real this time.
    From Jason Wang.

 5) Out-of-bounds access in powerpc ebpf tailcalls, from Daniel
    Borkmann.

 6) Fix phy_resume() locking, from Andrew Lunn.

 7) IFLA_MTU values are ignored on newlink for some tunnel types, fix
    from Xin Long.

 8) Revert F-RTO middle box workarounds, they only handle one dimension
    of the problem. From Yuchung Cheng.

 9) Fix socket refcounting in RDS, from Ka-Cheong Poon.

10) Don't allow ppp unit registration to an unregistered channel, from
    Guillaume Nault.

11) Various hv_netvsc fixes from Stephen Hemminger.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (98 commits)
  hv_netvsc: propagate rx filters to VF
  hv_netvsc: filter multicast/broadcast
  hv_netvsc: defer queue selection to VF
  hv_netvsc: use napi_schedule_irqoff
  hv_netvsc: fix race in napi poll when rescheduling
  hv_netvsc: cancel subchannel setup before halting device
  hv_netvsc: fix error unwind handling if vmbus_open fails
  hv_netvsc: only wake transmit queue if link is up
  hv_netvsc: avoid retry on send during shutdown
  virtio-net: re enable XDP_REDIRECT for mergeable buffer
  ppp: prevent unregistered channels from connecting to PPP units
  tc-testing: skbmod: fix match value of ethertype
  mlxsw: spectrum_switchdev: Check success of FDB add operation
  net: make skb_gso_*_seglen functions private
  net: xfrm: use skb_gso_validate_network_len() to check gso sizes
  net: sched: tbf: handle GSO_BY_FRAGS case in enqueue
  net: rename skb_gso_validate_mtu -> skb_gso_validate_network_len
  rds: Incorrect reference counting in TCP socket creation
  net: ethtool: don't ignore return from driver get_fecparam method
  vrf: check forwarding on the original netdevice when generating ICMP dest unreachable
  ...

Stephen Hemminger says:

====================
hv_netvsc: minor fixes

These are improvements to netvsc driver. They aren't functionality
changes so not targeting net-next; and they are not show stopper
bugs that need to go to stable either.

v2
   - drop the irq flags patch, defer it to net-next
   - split the multicast filter flag patch out
   - change propogate rx mode patch to handle startup of vf
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

The netvsc device should propagate filters to the SR-IOV VF
device (if present). The flags also need to be propagated to the
VF device as well. This only really matters on local Hyper-V
since Azure does not support multiple addresses.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The netvsc driver was always enabling all multicast and broadcast
even if netdevice flag had not enabled it.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When VF is used for accelerated networking it will likely have
more queues (and different policy) than the synthetic NIC.
This patch defers the queue policy to the VF so that all the
queues can be used. This impacts workloads like local generate UDP.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Since the netvsc_channel_cb is already called in interrupt
context from vmbus, there is no need to do irqsave/restore.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

There is a race between napi_reschedule and re-enabling interrupts
which could lead to missed host interrrupts.  This occurs when
interrupts are re-enabled (hv_end_read) and vmbus irq callback
(netvsc_channel_cb) has already scheduled NAPI.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Block setup of multiple channels earlier in the teardown
process. This avoids possible races between halt and subchannel
initialization.
Suggested-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Need to delete NAPI association if vmbus_open fails.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Don't wake transmit queues if link is not up yet.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Change the initialization order so that the device is ready to transmit
(ie connect vsp is completed) before setting the internal reference
to the device with RCU.

This avoids any races on initialization and prevents retry issues
on shutdown.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

XDP_REDIRECT support for mergeable buffer was removed since commit
7324f539 ("virtio_net: disable XDP_REDIRECT in receive_mergeable()
case"). This is because we don't reserve enough tailroom for struct
skb_shared_info which breaks XDP assumption. So this patch fixes this
by reserving enough tailroom and using fixed size of rx buffer.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

PPP units don't hold any reference on the channels connected to it.
It is the channel's responsibility to ensure that it disconnects from
its unit before being destroyed.
In practice, this is ensured by ppp_unregister_channel() disconnecting
the channel from the unit before dropping a reference on the channel.

However, it is possible for an unregistered channel to connect to a PPP
unit: register a channel with ppp_register_net_channel(), attach a
/dev/ppp file to it with ioctl(PPPIOCATTCHAN), unregister the channel
with ppp_unregister_channel() and finally connect the /dev/ppp file to
a PPP unit with ioctl(PPPIOCCONNECT).

Once in this situation, the channel is only held by the /dev/ppp file,
which can be released at anytime and free the channel without letting
the parent PPP unit know. Then the ppp structure ends up with dangling
pointers in its ->channels list.

Prevent this scenario by forbidding unregistered channels from
connecting to PPP units. This maintains the code logic by keeping
ppp_unregister_channel() responsible from disconnecting the channel if
necessary and avoids modification on the reference counting mechanism.

This issue seems to predate git history (successfully reproduced on
Linux 2.6.26 and earlier PPP commits are unrelated).
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

iproute2 print_skbmod() prints the configured ethertype using format 0x%X:
therefore, test 9aa8 systematically fails, because it configures action #4
using ethertype 0x0031, and expects 0x0031 when it reads it back. Changing
the expected value to 0x31 lets the test result 'not ok' become 'ok'.

tested with:
 # ./tdc.py -e 9aa8
 Test 9aa8: Get a single skbmod action from a list
 All test results:

 1..1
 ok 1 9aa8 Get a single skbmod action from a list

Fixes: cf797ac4 ("tc-testing: Add test cases for police and skbmod")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>