When core_kernel_text() is used to determine whether an address on a
task's stack trace is a kernel text address, it incorrectly returns
false for early text addresses for the head code between the _text and
_stext markers.  Among other things, this can cause the unwinder to
behave incorrectly when unwinding to x86 head code.

Head code is text code too, so mark it as such.  This seems to match the
intent of other users of the _stext symbol, and it also seems consistent
with what other architectures are already doing.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/789cf978866420e72fa89df44aa2849426ac378d.1474480779.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Thanks to all the recent x86 entry code refactoring, most tasks' kernel
stacks start at the same offset right below their saved pt_regs,
regardless of which syscall was used to enter the kernel.  That creates
a nice convention which makes it straightforward to identify the end of
the stack, which can be useful for the unwinder to verify the stack is
sane.

However, the boot CPU's idle "swapper" task doesn't follow that
convention.  Fix that by starting its stack at a sizeof(pt_regs) offset
from the end of the stack page.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/81aee3beb6ed88e44f1bea6986bb7b65c368f77a.1474480779.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

The frame at the end of each idle task stack has a zeroed return
address.  This is inconsistent with real task stacks, which have a real
return address at that spot.  This inconsistency can be confusing for
stack unwinders.  It also hides useful information about what asm code
was involved in calling into C.

Make it a real address by using the side effect of a call instruction to
push the instruction pointer on the stack.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/f59593ae7b15d5126f872b0a23143173d28aa32d.1474480779.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

There are two different pieces of code for starting a CPU: start_cpu0()
and the end of secondary_startup_64().  They're identical except for the
stack setup.  Combine the common parts into a shared start_cpu()
function.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1d692ffa62fcb3cc835a5b254e953f2d9bab3549.1474480779.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

On 32-bit kernels, the initial idle stack calculation doesn't take into
account the TOP_OF_KERNEL_STACK_PADDING, making the stack end address
inconsistent with other tasks on 32-bit.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/6cf569410bfa84cf923902fc4d628444cace94be.1474480779.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

The frame at the end of each idle task stack is inconsistent with real
task stacks, which have a stack frame header and a real return address
before the pt_regs area.  This inconsistency can be confusing for stack
unwinders.  It also hides useful information about what asm code was
involved in calling into C.

Fix that by changing the initial code jumps to calls.  Also add infinite
loops after the calls to make it clear that the calls don't return, and
to hang if they do.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/2588f34b6fbac4ae6f6f9ead2a78d7f8d58a6341.1474480779.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Thanks to all the recent x86 entry code refactoring, most tasks' kernel
stacks start at the same offset right below their saved pt_regs,
regardless of which syscall was used to enter the kernel.  That creates
a nice convention which makes it straightforward to identify the end of
the stack, which can be useful for the unwinder to verify the stack is
sane.

Calling schedule_tail() directly breaks that convention because its an
asmlinkage function so its argument has to be pushed on the stack.  Add
a wrapper which creates a proper "end of stack" frame header before the
call.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/ecafcd882676bf48ceaf50483782552bb98476e5.1474480779.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

The 'error_code' label is awkwardly named, especially when it shows up
in a stack trace.  Move it to its own local function and rename it to
'common_exception', analagous to the existing 'common_interrupt'.

This also makes related stack traces more sensible.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/cca1734a93e52799556d946281b32468f9b93950.1474480779.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Add the local label prefix to all non-function named labels in head_32.S
and entry_32.S.  In addition to decluttering the symbol table, it also
will help stack traces to be more sensible.  For example, the last
reported function in the idle task stack trace will be startup_32_smp()
instead of is486().
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/14f9f7afd478b23a762f40734da1a57c0c273f6e.1474480779.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20161019191108.2230-1-kuleshovmail@gmail.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Merge tag 'platform-drivers-x86-v4.9-2' of git://git.infradead.org/users/dvhart/linux-platform-drivers-x86

Pull x86 platform driver fixes from Darren Hart:
 "Fix a Kconfig issue leading potential link failure, and add a DMI
  match for an existing quirk.

  asus-wmi:
   - add SERIO_I8042 dependency

  ideapad-laptop:
   - Add Lenovo Yoga 910-13IKB to no_hw_rfkill dmi list"

* tag 'platform-drivers-x86-v4.9-2' of git://git.infradead.org/users/dvhart/linux-platform-drivers-x86:
  platform/x86: asus-wmi: add SERIO_I8042 dependency
  platform/x86: ideapad-laptop: Add Lenovo Yoga 910-13IKB to no_hw_rfkill dmi list

Pull arch/sh updates from Rich Felker:
 "Minor changes to improve J2 support and match Kconfig expectations of
  other subsystems"

* tag 'sh-for-4.9' of git://git.libc.org/linux-sh:
  sh: add earlycon support to j2_defconfig
  sh: add Kconfig option for J-Core SoC core drivers
  sh: support CPU_J2 when compiler lacks -mj2

Pull scheduler fix from Ingo Molnar:
 "This fixes a group scheduling related performance/interactivity
  regression introduced in v4.8, which affects certain hardware
  environments where cpu_possible_mask != cpu_present_mask"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Fix incorrect task group ->load_avg

Pull HID fixes from Jiri Kosina:

 - hid-dr regression fix for certain dragonrise gamepads (device ID
   0079:0006), from Ioan-Adrian Ratiu

 - dma-on-stack fix for hid-led driver, from Heiner Kallweit

 - quirk for Akai MIDImix device

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid:
  HID: add quirk for Akai MIDImix.
  Revert "HID: dragonrise: fix HID Descriptor for 0x0006 PID"
  HID: hid-dr: add input mapping for axis selection
  HID: hid-led: fix issue with transfer buffer not being dma capable

Pull first round of pin control fixes from Linus Walleij:

 - a bunch of barnsjukdomar/kinderkrankheiten/maladie infantile in the
   Aspeed driver. (Why doesn't English have a word for this?)

   [ Maybe "teething problems" is the closest English idiom? - Linus T ]

 - fix a lockdep bug on the Intel BayTrail.

 - fix a few special laptop issues on the Intel pin controller solving
   suspend issues.

* tag 'pinctrl-v4.9-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl:
  pinctrl: intel: Only restore pins that are used by the driver
  pinctrl: baytrail: Fix lockdep
  pinctrl: aspeed-g5: Fix pin association of SPI1 function
  pinctrl: aspeed-g5: Fix GPIOE1 typo
  pinctrl: aspeed-g5: Fix names of GPID2 pins
  pinctrl: aspeed: "Not enabled" is a significant mux state

We have a fairly common pattern where you print several things as
continuations on one single line in a loop, and then at the end you do

	printk(KERN_CONT "\n");

to flush the buffered output.

But if the output was flushed by something else (concurrent printk
activity, or just system logging), we don't want that final flushing to
just print an empty line.

So just suppress empty continuation lines when they couldn't be merged
into the line they are a continuation of.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Merge the gup_flags cleanups from Lorenzo Stoakes:
 "This patch series adjusts functions in the get_user_pages* family such
  that desired FOLL_* flags are passed as an argument rather than
  implied by flags.

  The purpose of this change is to make the use of FOLL_FORCE explicit
  so it is easier to grep for and clearer to callers that this flag is
  being used.  The use of FOLL_FORCE is an issue as it overrides missing
  VM_READ/VM_WRITE flags for the VMA whose pages we are reading
  from/writing to, which can result in surprising behaviour.

  The patch series came out of the discussion around commit 38e08854
  ("mm: check VMA flags to avoid invalid PROT_NONE NUMA balancing"),
  which addressed a BUG_ON() being triggered when a page was faulted in
  with PROT_NONE set but having been overridden by FOLL_FORCE.
  do_numa_page() was run on the assumption the page _must_ be one marked
  for NUMA node migration as an actual PROT_NONE page would have been
  dealt with prior to this code path, however FOLL_FORCE introduced a
  situation where this assumption did not hold.

  See

      https://marc.info/?l=linux-mm&m=147585445805166

  for the patch proposal"

Additionally, there's a fix for an ancient bug related to FOLL_FORCE and
FOLL_WRITE by me.

[ This branch was rebased recently to add a few more acked-by's and
  reviewed-by's ]

* gup_flag-cleanups:
  mm: replace access_process_vm() write parameter with gup_flags
  mm: replace access_remote_vm() write parameter with gup_flags
  mm: replace __access_remote_vm() write parameter with gup_flags
  mm: replace get_user_pages_remote() write/force parameters with gup_flags
  mm: replace get_user_pages() write/force parameters with gup_flags
  mm: replace get_vaddr_frames() write/force parameters with gup_flags
  mm: replace get_user_pages_locked() write/force parameters with gup_flags
  mm: replace get_user_pages_unlocked() write/force parameters with gup_flags
  mm: remove write/force parameters from __get_user_pages_unlocked()
  mm: remove write/force parameters from __get_user_pages_locked()
  mm: remove gup_flags FOLL_WRITE games from __get_user_pages()

This removes the 'write' argument from access_process_vm() and replaces
it with 'gup_flags' as use of this function previously silently implied
FOLL_FORCE, whereas after this patch callers explicitly pass this flag.

We make this explicit as use of FOLL_FORCE can result in surprising
behaviour (and hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This removes the 'write' argument from access_remote_vm() and replaces
it with 'gup_flags' as use of this function previously silently implied
FOLL_FORCE, whereas after this patch callers explicitly pass this flag.

We make this explicit as use of FOLL_FORCE can result in surprising
behaviour (and hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This removes the 'write' argument from __access_remote_vm() and replaces
it with 'gup_flags' as use of this function previously silently implied
FOLL_FORCE, whereas after this patch callers explicitly pass this flag.

We make this explicit as use of FOLL_FORCE can result in surprising
behaviour (and hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This removes the 'write' and 'force' from get_user_pages_remote() and
replaces them with 'gup_flags' to make the use of FOLL_FORCE explicit in
callers as use of this flag can result in surprising behaviour (and
hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This removes the 'write' and 'force' from get_user_pages() and replaces
them with 'gup_flags' to make the use of FOLL_FORCE explicit in callers
as use of this flag can result in surprising behaviour (and hence bugs)
within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This removes the 'write' and 'force' from get_vaddr_frames() and
replaces them with 'gup_flags' to make the use of FOLL_FORCE explicit in
callers as use of this flag can result in surprising behaviour (and
hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This removes the 'write' and 'force' use from get_user_pages_locked()
and replaces them with 'gup_flags' to make the use of FOLL_FORCE
explicit in callers as use of this flag can result in surprising
behaviour (and hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

A scheduler performance regression has been reported by Joseph Salisbury,
which he bisected back to:

  3d30544f ("sched/fair: Apply more PELT fixes)

The regression triggers when several levels of task groups are involved
(read: SystemD) and cpu_possible_mask != cpu_present_mask.

The root cause is that group entity's load (tg_child->se[i]->avg.load_avg)
is initialized to scale_load_down(se->load.weight). During the creation of
a child task group, its group entities on possible CPUs are attached to
parent's cfs_rq (tg_parent) and their loads are added to the parent's load
(tg_parent->load_avg) with update_tg_load_avg().

But only the load on online CPUs will then be updated to reflect real load,
whereas load on other CPUs will stay at the initial value.

The result is a tg_parent->load_avg that is higher than the real load, the
weight of group entities (tg_parent->se[i]->load.weight) on online CPUs is
smaller than it should be, and the task group gets a less running time than
what it could expect.

( This situation can be detected with /proc/sched_debug. The ".tg_load_avg"
  of the task group will be much higher than sum of ".tg_load_avg_contrib"
  of online cfs_rqs of the task group. )

The load of group entities don't have to be intialized to something else
than 0 because their load will increase when an entity is attached.
Reported-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@vger.kernel.org> # 4.8.x
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: joonwoop@codeaurora.org
Fixes: 3d30544f ("sched/fair: Apply more PELT fixes)
Link: http://lkml.kernel.org/r/1476881123-10159-1-git-send-email-vincent.guittot@linaro.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

Signed-off-by: Rich Felker <dalias@libc.org>

Signed-off-by: Rich Felker <dalias@libc.org>

Pull f2fs bugfix from Jaegeuk Kim:
 "This fixes a bug which referenced the wrong pointer, sum_page, in
  f2fs_gc.  It was newly introduced in 4.9-rc1.

* tag 'for-f2fs-4.9-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs:
  f2fs: fix wrong sum_page pointer in f2fs_gc

This removes the 'write' and 'force' use from get_user_pages_unlocked()
and replaces them with 'gup_flags' to make the use of FOLL_FORCE
explicit in callers as use of this flag can result in surprising
behaviour (and hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This removes the redundant 'write' and 'force' parameters from
__get_user_pages_unlocked() to make the use of FOLL_FORCE explicit in
callers as use of this flag can result in surprising behaviour (and
hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This removes the redundant 'write' and 'force' parameters from
__get_user_pages_locked() to make the use of FOLL_FORCE explicit in
callers as use of this flag can result in surprising behaviour (and
hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This is an ancient bug that was actually attempted to be fixed once
(badly) by me eleven years ago in commit 4ceb5db9 ("Fix
get_user_pages() race for write access") but that was then undone due to
problems on s390 by commit f33ea7f4 ("fix get_user_pages bug").

In the meantime, the s390 situation has long been fixed, and we can now
fix it by checking the pte_dirty() bit properly (and do it better).  The
s390 dirty bit was implemented in abf09bed ("s390/mm: implement
software dirty bits") which made it into v3.9.  Earlier kernels will
have to look at the page state itself.

Also, the VM has become more scalable, and what used a purely
theoretical race back then has become easier to trigger.

To fix it, we introduce a new internal FOLL_COW flag to mark the "yes,
we already did a COW" rather than play racy games with FOLL_WRITE that
is very fundamental, and then use the pte dirty flag to validate that
the FOLL_COW flag is still valid.
Reported-and-tested-by: Phil "not Paul" Oester <kernel@linuxace.com>
Acked-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Michal Hocko <mhocko@suse.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull x86 fixes from Ingo Molnar:
 "Misc fixes, plus hw-enablement changes:

   - fix persistent RAM handling
   - remove pkeys warning
   - remove duplicate macro
   - fix debug warning in irq handler
   - add new 'Knights Mill' CPU related constants and enable the perf bits"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/intel/uncore: Add Knights Mill CPUID
  perf/x86/intel/rapl: Add Knights Mill CPUID
  perf/x86/intel: Add Knights Mill CPUID
  x86/cpu/intel: Add Knights Mill to Intel family
  x86/e820: Don't merge consecutive E820_PRAM ranges
  pkeys: Remove easily triggered WARN
  x86: Remove duplicate rtit status MSR macro
  x86/smp: Add irq_enter/exit() in smp_reschedule_interrupt()

Pull timer fixlet from Ingo Molnar:
 "Remove an unused variable"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  alarmtimer: Remove unused but set variable

Pull scheduler fix from Ingo Molnar:
 "Fix a crash that can trigger when racing with CPU hotplug: we didn't
  use sched-domains data structures carefully enough in select_idle_cpu()"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Fix sched domains NULL dereference in select_idle_sibling()

Pull perf fixes from Ingo Molnar:
 "Four tooling fixes, two kprobes KASAN related fixes and an x86 PMU
  driver fix/cleanup"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf jit: Fix build issue on Ubuntu
  perf jevents: Handle events including .c and .o
  perf/x86/intel: Remove an inconsistent NULL check
  kprobes: Unpoison stack in jprobe_return() for KASAN
  kprobes: Avoid false KASAN reports during stack copy
  perf header: Set nr_numa_nodes only when we parsed all the data
  perf top: Fix refreshing hierarchy entries on TUI

Pull locking fixes from Ingo Molnar:
 "Two fixes:

   - a file locks fix (missing critical section, bug introduced in this
     merge window)

   - an x86 down_write() stack frame annotation"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking, fs/locks: Add missing file_sem locks
  locking/rwsem/x86: Add stack frame dependency for ____down_write()

Pull irq fixes from Ingo Molnar:
 "Three irqchip driver fixes"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/gicv3: Handle loop timeout proper
  irqchip/jcore: Fix lost per-cpu interrupts
  irqchip/eznps: Acknowledge NPS_IPI before calling the handler

Pull misc fixes from Ingo Molnar:
 "A CPU hotplug debuggability fix and three objtool false positive
  warnings fixes for new GCC6 code generation patterns"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpu/hotplug: Use distinct name for cpu_hotplug.dep_map
  objtool: Skip all "unreachable instruction" warnings for gcov kernels
  objtool: Improve rare switch jump table pattern detection
  objtool: Support '-mtune=atom' stack frame setup instruction

Pull firewire fixlet from Stefan Richter:
 "IEEE 1394 subsystem patch: catch an initialization error in the packet
  sniffer nosy"

* tag 'firewire-update' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394:
  firewire: nosy: do not ignore errors in ioremap_nocache()