From the GCC manual:

  copy
  copy(function)

    The copy attribute applies the set of attributes with which function
    has been declared to the declaration of the function to which
    the attribute is applied. The attribute is designed for libraries
    that define aliases or function resolvers that are expected
    to specify the same set of attributes as their targets. The copy
    attribute can be used with functions, variables, or types. However,
    the kind of symbol to which the attribute is applied (either
    function or variable) must match the kind of symbol to which
    the argument refers. The copy attribute copies only syntactic and
    semantic attributes but not attributes that affect a symbol’s
    linkage or visibility such as alias, visibility, or weak.
    The deprecated attribute is also not copied.

  https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html

The upcoming GCC 9 release extends the -Wmissing-attributes warnings
(enabled by -Wall) to C and aliases: it warns when particular function
attributes are missing in the aliases but not in their target, e.g.:

    void __cold f(void) {}
    void __alias("f") g(void);

diagnoses:

    warning: 'g' specifies less restrictive attribute than
    its target 'f': 'cold' [-Wmissing-attributes]

Using __copy(f) we can copy the __cold attribute from f to g:

    void __cold f(void) {}
    void __copy(f) __alias("f") g(void);

This attribute is most useful to deal with situations where an alias
is declared but we don't know the exact attributes the target has.

For instance, in the kernel, the widely used module_init/exit macros
define the init/cleanup_module aliases, but those cannot be marked
always as __init/__exit since some modules do not have their
functions marked as such.
Suggested-by: NMartin Sebor <msebor@gcc.gnu.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: NMiguel Ojeda <miguel.ojeda.sandonis@gmail.com>

The upcoming GCC 9 release extends the -Wmissing-attributes warnings
(enabled by -Wall) to C and aliases: it warns when particular function
attributes are missing in the aliases but not in their target.

In particular, it triggers here because crc32_le_base/__crc32c_le_base
aren't __pure while their target crc32_le/__crc32c_le are.

These aliases are used by architectures as a fallback in accelerated
versions of CRC32. See commit 9784d82d ("lib/crc32: make core crc32()
routines weak so they can be overridden").

Therefore, being fallbacks, it is likely that even if the aliases
were called from C, there wouldn't be any optimizations possible.
Currently, the only user is arm64, which calls this from asm.

Still, marking the aliases as __pure makes sense and is a good idea
for documentation purposes and possible future optimizations,
which also silences the warning.
Acked-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: NLaura Abbott <labbott@redhat.com>
Signed-off-by: NMiguel Ojeda <miguel.ojeda.sandonis@gmail.com>

Pull x86 fixes from Thomas Gleixner:
 "A few updates for x86:

   - Fix an unintended sign extension issue in the fault handling code

   - Rename the new resource control config switch so it's less
     confusing

   - Avoid setting up EFI info in kexec when the EFI runtime is
     disabled.

   - Fix the microcode version check in the AMD microcode loader so it
     only loads higher version numbers and never downgrades

   - Set EFER.LME in the 32bit trampoline before returning to long mode
     to handle older AMD/KVM behaviour properly.

   - Add Darren and Andy as x86/platform reviewers"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/resctrl: Avoid confusion over the new X86_RESCTRL config
  x86/kexec: Don't setup EFI info if EFI runtime is not enabled
  x86/microcode/amd: Don't falsely trick the late loading mechanism
  MAINTAINERS: Add Andy and Darren as arch/x86/platform/ reviewers
  x86/fault: Fix sign-extend unintended sign extension
  x86/boot/compressed/64: Set EFER.LME=1 in 32-bit trampoline before returning to long mode
  x86/cpu: Add Atom Tremont (Jacobsville)

Pull cpu hotplug fixes from Thomas Gleixner:
 "Two fixes for the cpu hotplug machinery:

   - Replace the overly clever 'SMT disabled by BIOS' detection logic as
     it breaks KVM scenarios and prevents speculation control updates
     when the Hyperthreads are brought online late after boot.

   - Remove a redundant invocation of the speculation control update
     function"

* 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM
  x86/speculation: Remove redundant arch_smt_update() invocation

Pull perf fixes from Thomas Gleixner:
 "A pile of perf updates:

   - Fix broken sanity check in the /proc/sys/kernel/perf_cpu_time_max_percent
     write handler

   - Cure a perf script crash which caused by an unitinialized data
     structure

   - Highlight the hottest instruction in perf top and not a random one

   - Cure yet another clang issue when building perf python

   - Handle topology entries with no CPU correctly in the tools

   - Handle perf data which contains both tracepoints and performance
     counter entries correctly.

   - Add a missing NULL pointer check in perf ordered_events_free()"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf script: Fix crash when processing recorded stat data
  perf top: Fix wrong hottest instruction highlighted
  perf tools: Handle TOPOLOGY headers with no CPU
  perf python: Remove -fstack-clash-protection when building with some clang versions
  perf core: Fix perf_proc_update_handler() bug
  perf script: Fix crash with printing mixed trace point and other events
  perf ordered_events: Fix crash in ordered_events__free

Pull EFI fix from Thomas Gleixner:
 "The dump info for the efi page table debugging lacks a terminator
  which causes the kernel to crash when the debugfile is read"

* 'efi-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  efi/arm64: Fix debugfs crash by adding a terminator for ptdump marker

Pull btrfs fixes from David Sterba:

 - regression fix: transaction commit can run away due to delayed ref
   waiting heuristic, this is not necessary now because of the proper
   reservation mechanism introduced in 5.0

 - regression fix: potential crash due to use-before-check of an ERR_PTR
   return value

 - fix for transaction abort during transaction commit that needs to
   properly clean up pending block groups

 - fix deadlock during b-tree node/leaf splitting, when this happens on
   some of the fundamental trees, we must prevent new tree block
   allocation to re-enter indirectly via the block group flushing path

 - potential memory leak after errors during mount

* tag 'for-5.0-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: On error always free subvol_name in btrfs_mount
  btrfs: clean up pending block groups when transaction commit aborts
  btrfs: fix potential oops in device_list_add
  btrfs: don't end the transaction for delayed refs in throttle
  Btrfs: fix deadlock when allocating tree block during leaf/node split

Pull Devicetree fix from Rob Herring:
 "A single fix for building DT bindings in-tree"

* tag 'devicetree-fixes-for-5.0-3' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux:
  dt-bindings: Fix dt_binding_check target for in tree builds

Merge tag 'riscv-for-linus-5.0-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux

Pull RISC-V fixes from Palmer Dabbelt:
 "This contains a handful of mostly-independent patches:

   - make our port respect TIF_NEED_RESCHED, which fixes
     CONFIG_PREEMPT=y kernels

   - fix double-put of OF nodes

   - fix a misspelling of target in our Kconfig

   - generic PCIe is enabled in our defconfig

   - fix our SBI early console to properly handle line
     endings

   - fix max_low_pfn being counted in PFNs

   - a change to TASK_UNMAPPED_BASE to match what other
     arches do

  This has passed my standard 'boot Fedora' flow"

* tag 'riscv-for-linus-5.0-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux:
  riscv: Adjust mmap base address at a third of task size
  riscv: fixup max_low_pfn with PFN_DOWN.
  tty/serial: use uart_console_write in the RISC-V SBL early console
  RISC-V: defconfig: Add CRYPTO_DEV_VIRTIO=y
  RISC-V: defconfig: Enable Generic PCIE by default
  RISC-V: defconfig: Move CONFIG_PCI{,E_XILINX}
  RISC-V: Kconfig: fix spelling mistake "traget" -> "target"
  RISC-V: asm/page.h: fix spelling mistake "CONFIG_64BITS" -> "CONFIG_64BIT"
  RISC-V: fix bad use of of_node_put
  RISC-V: Add _TIF_NEED_RESCHED check for kernel thread when CONFIG_PREEMPT=y

Pull block fixes from Jens Axboe:
 "A few fixes that should go into this release. This contains:

   - MD pull request from Song, fixing a recovery OOM issue (Alexei)

   - Fix for a sync related stall (Jianchao)

   - Dummy callback for timeouts (Tetsuo)

   - IDE atapi sense ordering fix (me)"

* tag 'for-linus-20190202' of git://git.kernel.dk/linux-block:
  ide: ensure atapi sense request aren't preempted
  blk-mq: fix a hung issue when fsync
  block: pass no-op callback to INIT_WORK().
  md/raid5: fix 'out of memory' during raid cache recovery

Pull SCSI fixes from James Bottomley:
 "Five minor bug fixes.

  The libfc one is a tiny memory leak, the zfcp one is an incorrect user
  visible parameter and the rest are on error legs or obscure features"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: 53c700: pass correct "dev" to dma_alloc_attrs()
  scsi: bnx2fc: Fix error handling in probe()
  scsi: scsi_debug: fix write_same with virtual_gb problem
  scsi: libfc: free skb when receiving invalid flogi resp
  scsi: zfcp: fix sysfs block queue limit output for max_segment_size

Merge misc fixes from Andrew Morton:
 "24 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (24 commits)
  autofs: fix error return in autofs_fill_super()
  autofs: drop dentry reference only when it is never used
  fs/drop_caches.c: avoid softlockups in drop_pagecache_sb()
  mm: migrate: don't rely on __PageMovable() of newpage after unlocking it
  psi: clarify the Kconfig text for the default-disable option
  mm, memory_hotplug: __offline_pages fix wrong locking
  mm: hwpoison: use do_send_sig_info() instead of force_sig()
  kasan: mark file common so ftrace doesn't trace it
  init/Kconfig: fix grammar by moving a closing parenthesis
  lib/test_kmod.c: potential double free in error handling
  mm, oom: fix use-after-free in oom_kill_process
  mm/hotplug: invalid PFNs from pfn_to_online_page()
  mm,memory_hotplug: fix scan_movable_pages() for gigantic hugepages
  psi: fix aggregation idle shut-off
  mm, memory_hotplug: test_pages_in_a_zone do not pass the end of zone
  mm, memory_hotplug: is_mem_section_removable do not pass the end of a zone
  oom, oom_reaper: do not enqueue same task twice
  mm: migrate: make buffer_migrate_page_norefs() actually succeed
  kernel/exit.c: release ptraced tasks before zap_pid_ns_processes
  x86_64: increase stack size for KASAN_EXTRA
  ...

When reading 'efi_page_tables' debugfs triggers an out-of-bounds access here:

  arch/arm64/mm/dump.c: 282
  if (addr >= st->marker[1].start_address) {

called from:

  arch/arm64/mm/dump.c: 331
  note_page(st, addr, 2, pud_val(pud));

because st->marker++ is is called after "UEFI runtime end" which is the
last element in addr_marker[]. Therefore, add a terminator like the one
for kernel_page_tables, so it can be skipped to print out non-existent
markers.

Here's the KASAN bug report:

  # cat /sys/kernel/debug/efi_page_tables
  ---[ UEFI runtime start ]---
  0x0000000020000000-0x0000000020010000          64K PTE       RW NX SHD AF ...
  0x0000000020200000-0x0000000021340000       17664K PTE       RW NX SHD AF ...
  ...
  0x0000000021920000-0x0000000021950000         192K PTE       RW x  SHD AF ...
  0x0000000021950000-0x00000000219a0000         320K PTE       RW NX SHD AF ...
  ---[ UEFI runtime end ]---
  ---[ (null) ]---
  ---[ (null) ]---

   BUG: KASAN: global-out-of-bounds in note_page+0x1f0/0xac0
   Read of size 8 at addr ffff2000123f2ac0 by task read_all/42464
   Call trace:
    dump_backtrace+0x0/0x298
    show_stack+0x24/0x30
    dump_stack+0xb0/0xdc
    print_address_description+0x64/0x2b0
    kasan_report+0x150/0x1a4
    __asan_report_load8_noabort+0x30/0x3c
    note_page+0x1f0/0xac0
    walk_pgd+0xb4/0x244
    ptdump_walk_pgd+0xec/0x140
    ptdump_show+0x40/0x50
    seq_read+0x3f8/0xad0
    full_proxy_read+0x9c/0xc0
    __vfs_read+0xfc/0x4c8
    vfs_read+0xec/0x208
    ksys_read+0xd0/0x15c
    __arm64_sys_read+0x84/0x94
    el0_svc_handler+0x258/0x304
    el0_svc+0x8/0xc

  The buggy address belongs to the variable:
   __compound_literal.0+0x20/0x800

  Memory state around the buggy address:
   ffff2000123f2980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
   ffff2000123f2a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa
  >ffff2000123f2a80: fa fa fa fa 00 00 00 00 fa fa fa fa 00 00 00 00
                                            ^
   ffff2000123f2b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
   ffff2000123f2b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0

[ ardb: fix up whitespace ]
[ mingo: fix up some moar ]
Signed-off-by: NQian Cai <cai@lca.pw>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Fixes: 9d80448a ("efi/arm64: Add debugfs node to dump UEFI runtime page tables")
Link: http://lkml.kernel.org/r/20190202095017.13799-2-ard.biesheuvel@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

"Resource Control" is a very broad term for this CPU feature, and a term
that is also associated with containers, cgroups etc. This can easily
cause confusion.

Make the user prompt more specific. Match the config symbol name.

 [ bp: In the future, the corresponding ARM arch-specific code will be
   under ARM_CPU_RESCTRL and the arch-agnostic bits will be carved out
   under the CPU_RESCTRL umbrella symbol. ]
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Cc: Babu Moger <Babu.Moger@amd.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Morse <james.morse@arm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: linux-doc@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pu Wen <puwen@hygon.cn>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190130195621.GA30653@cmpxchg.org

Pull xtensa fixes from Max Filippov:

 - fix ccount_timer_shutdown for secondary CPUs

 - fix secondary CPU initialization

 - fix secondary CPU reset vector clash with double exception vector

 - fix present CPUs when booting with 'maxcpus' parameter

 - limit possible CPUs by configured NR_CPUS

 - issue a warning if xtensa PIC is asked to retrigger anything other
   than software IRQ

 - fix masking/unmasking of the first two IRQs on xtensa MX PIC

 - fix typo in Kconfig description for user space unaligned access
   feature

 - fix Kconfig warning for selecting BUILTIN_DTB

* tag 'xtensa-20190201' of git://github.com/jcmvbkbc/linux-xtensa:
  xtensa: SMP: limit number of possible CPUs by NR_CPUS
  xtensa: rename BUILTIN_DTB to BUILTIN_DTB_SOURCE
  xtensa: Fix typo use space=>user space
  drivers/irqchip: xtensa-mx: fix mask and unmask
  drivers/irqchip: xtensa: add warning to irq_retrigger
  xtensa: SMP: mark each possible CPU as present
  xtensa: smp_lx200_defconfig: fix vectors clash
  xtensa: SMP: fix secondary CPU initialization
  xtensa: SMP: fix ccount_timer_shutdown

Pull arm64 fixes from Will Deacon:
 "Although we're still debugging a few minor arm64-specific issues in
  mainline, I didn't want to hold this lot up in the meantime.

  We've got an additional KASLR fix after the previous one wasn't quite
  complete, a fix for a performance regression when mapping executable
  pages into userspace and some fixes for kprobe blacklisting. All
  candidates for stable.

  Summary:

   - Fix module loading when KASLR is configured but disabled at runtime

   - Fix accidental IPI when mapping user executable pages

   - Ensure hyp-stub and KVM world switch code cannot be kprobed"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: hibernate: Clean the __hyp_text to PoC after resume
  arm64: hyp-stub: Forbid kprobing of the hyp-stub
  arm64: kprobe: Always blacklist the KVM world-switch code
  arm64: kaslr: ensure randomized quantities are clean also when kaslr is off
  arm64: Do not issue IPIs for user executable ptes

Pull smb3 fixes from Steve French:
 "SMB3 fixes, some from this week's SMB3 test evemt, 5 for stable and a
  particularly important one for queryxattr (see xfstests 70 and 117)"

* tag '5.0-rc4-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: update internal module version number
  CIFS: fix use-after-free of the lease keys
  CIFS: Do not consider -ENODATA as stat failure for reads
  CIFS: Do not count -ENODATA as failure for query directory
  CIFS: Fix trace command logging for SMB2 reads and writes
  CIFS: Fix possible oops and memory leaks in async IO
  cifs: limit amount of data we request for xattrs to CIFSMaxBufSize
  cifs: fix computation for MAX_SMB2_HDR_SIZE

Merge tag 'apparmor-pr-2019-02-01' of git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor

Pull apparmor bug fixes from John Johansen:
 "Two bug fixes for apparmor:

   - Fix aa_label_build() error handling for failed merges

   - Fix warning about unused function apparmor_ipv6_postroute"

* tag 'apparmor-pr-2019-02-01' of git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor:
  apparmor: Fix aa_label_build() error handling for failed merges
  apparmor: Fix warning about unused function apparmor_ipv6_postroute

In autofs_fill_super() on error of get inode/make root dentry the return
should be ENOMEM as this is the only failure case of the called
functions.

Link: http://lkml.kernel.org/r/154725123240.11260.796773942606871359.stgit@pluto-themaw-netSigned-off-by: NIan Kent <raven@themaw.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

autofs_expire_run() calls dput(dentry) to drop the reference count of
dentry.  However, dentry is read via autofs_dentry_ino(dentry) after
that.  This may result in a use-free-bug.  The patch drops the reference
count of dentry only when it is never used.

Link: http://lkml.kernel.org/r/154725122396.11260.16053424107144453867.stgit@pluto-themaw-netSigned-off-by: NPan Bian <bianpan2016@163.com>
Signed-off-by: NIan Kent <raven@themaw.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When superblock has lots of inodes without any pagecache (like is the
case for /proc), drop_pagecache_sb() will iterate through all of them
without dropping sb->s_inode_list_lock which can lead to softlockups
(one of our customers hit this).

Fix the problem by going to the slow path and doing cond_resched() in
case the process needs rescheduling.

Link: http://lkml.kernel.org/r/20190114085343.15011-1-jack@suse.czSigned-off-by: NJan Kara <jack@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We had a race in the old balloon compaction code before b1123ea6
("mm: balloon: use general non-lru movable page feature") refactored it
that became visible after backporting 195a8c43 ("virtio-balloon:
deflate via a page list") without the refactoring.

The bug existed from commit d6d86c0a ("mm/balloon_compaction:
redesign ballooned pages management") till b1123ea6 ("mm: balloon:
use general non-lru movable page feature").  d6d86c0a
("mm/balloon_compaction: redesign ballooned pages management") was
backported to 3.12, so the broken kernels are stable kernels [3.12 -
4.7].

There was a subtle race between dropping the page lock of the newpage in
__unmap_and_move() and checking for __is_movable_balloon_page(newpage).

Just after dropping this page lock, virtio-balloon could go ahead and
deflate the newpage, effectively dequeueing it and clearing PageBalloon,
in turn making __is_movable_balloon_page(newpage) fail.

This resulted in dropping the reference of the newpage via
putback_lru_page(newpage) instead of put_page(newpage), leading to
page->lru getting modified and a !LRU page ending up in the LRU lists.
With 195a8c43 ("virtio-balloon: deflate via a page list")
backported, one would suddenly get corrupted lists in
release_pages_balloon():

- WARNING: CPU: 13 PID: 6586 at lib/list_debug.c:59 __list_del_entry+0xa1/0xd0
- list_del corruption. prev->next should be ffffe253961090a0, but was dead000000000100

Nowadays this race is no longer possible, but it is hidden behind very
ugly handling of __ClearPageMovable() and __PageMovable().

__ClearPageMovable() will not make __PageMovable() fail, only
PageMovable().  So the new check (__PageMovable(newpage)) will still
hold even after newpage was dequeued by virtio-balloon.

If anybody would ever change that special handling, the BUG would be
introduced again.  So instead, make it explicit and use the information
of the original isolated page before migration.

This patch can be backported fairly easy to stable kernels (in contrast
to the refactoring).

Link: http://lkml.kernel.org/r/20190129233217.10747-1-david@redhat.com
Fixes: d6d86c0a ("mm/balloon_compaction: redesign ballooned pages management")
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Reported-by: NVratislav Bendel <vbendel@redhat.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NRafael Aquini <aquini@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vratislav Bendel <vbendel@redhat.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: <stable@vger.kernel.org>	[3.12 - 4.7]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The current help text caused some confusion in online forums about
whether or not to default-enable or default-disable psi in vendor
kernels.  This is because it doesn't communicate the reason for why we
made this setting configurable in the first place: that the overhead is
non-zero in an artificial scheduler stress test.

Since this isn't representative of real workloads, and the effect was
not measurable in scheduler-heavy real world applications such as the
webservers and memcache installations at Facebook, it's fair to point
out that this is a pretty cautious option to select.

Link: http://lkml.kernel.org/r/20190129233617.16767-1-hannes@cmpxchg.orgSigned-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Jan has noticed that we do double unlock on some failure paths when
offlining a page range.  This is indeed the case when
test_pages_in_a_zone respp.  start_isolate_page_range fail.  This was an
omission when forward porting the debugging patch from an older kernel.

Fix the issue by dropping mem_hotplug_done from the failure condition
and keeping the single unlock in the catch all failure path.

Link: http://lkml.kernel.org/r/20190115120307.22768-1-mhocko@kernel.org
Fixes: 79605093 ("mm, memory_hotplug: print reason for the offlining failure")
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Reported-by: NJan Kara <jack@suse.cz>
Reviewed-by: NJan Kara <jack@suse.cz>
Tested-by: NJan Kara <jack@suse.cz>
Reviewed-by: NOscar Salvador <osalvador@suse.de>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently memory_failure() is racy against process's exiting, which
results in kernel crash by null pointer dereference.

The root cause is that memory_failure() uses force_sig() to forcibly
kill asynchronous (meaning not in the current context) processes.  As
discussed in thread https://lkml.org/lkml/2010/6/8/236 years ago for OOM
fixes, this is not a right thing to do.  OOM solves this issue by using
do_send_sig_info() as done in commit d2d39309 ("signal:
oom_kill_task: use SEND_SIG_FORCED instead of force_sig()"), so this
patch is suggesting to do the same for hwpoison.  do_send_sig_info()
properly accesses to siglock with lock_task_sighand(), so is free from
the reported race.

I confirmed that the reported bug reproduces with inserting some delay
in kill_procs(), and it never reproduces with this patch.

Note that memory_failure() can send another type of signal using
force_sig_mceerr(), and the reported race shouldn't happen on it because
force_sig_mceerr() is called only for synchronous processes (i.e.
BUS_MCEERR_AR happens only when some process accesses to the corrupted
memory.)

Link: http://lkml.kernel.org/r/20190116093046.GA29835@hori1.linux.bs1.fc.nec.co.jpSigned-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reported-by: NJane Chu <jane.chu@oracle.com>
Reviewed-by: NDan Williams <dan.j.williams@intel.com>
Reviewed-by: NWilliam Kucharski <william.kucharski@oracle.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When option CONFIG_KASAN is enabled toghether with ftrace, function
ftrace_graph_caller() gets in to a recursion, via functions
kasan_check_read() and kasan_check_write().

 Breakpoint 2, ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:179
 179             mcount_get_pc             x0    //     function's pc
 (gdb) bt
 #0  ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:179
 #1  0xffffff90101406c8 in ftrace_caller () at ../arch/arm64/kernel/entry-ftrace.S:151
 #2  0xffffff90106fd084 in kasan_check_write (p=0xffffffc06c170878, size=4) at ../mm/kasan/common.c:105
 #3  0xffffff90104a2464 in atomic_add_return (v=<optimized out>, i=<optimized out>) at ./include/generated/atomic-instrumented.h:71
 #4  atomic_inc_return (v=<optimized out>) at ./include/generated/atomic-fallback.h:284
 #5  trace_graph_entry (trace=0xffffffc03f5ff380) at ../kernel/trace/trace_functions_graph.c:441
 #6  0xffffff9010481774 in trace_graph_entry_watchdog (trace=<optimized out>) at ../kernel/trace/trace_selftest.c:741
 #7  0xffffff90104a185c in function_graph_enter (ret=<optimized out>, func=<optimized out>, frame_pointer=18446743799894897728, retp=<optimized out>) at ../kernel/trace/trace_functions_graph.c:196
 #8  0xffffff9010140628 in prepare_ftrace_return (self_addr=18446743592948977792, parent=0xffffffc03f5ff418, frame_pointer=18446743799894897728) at ../arch/arm64/kernel/ftrace.c:231
 #9  0xffffff90101406f4 in ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:182
 Backtrace stopped: previous frame identical to this frame (corrupt stack?)
 (gdb)

Rework so that the kasan implementation isn't traced.

Link: http://lkml.kernel.org/r/20181212183447.15890-1-anders.roxell@linaro.orgSigned-off-by: NAnders Roxell <anders.roxell@linaro.org>
Acked-by: NDmitry Vyukov <dvyukov@google.com>
Tested-by: NDmitry Vyukov <dvyukov@google.com>
Acked-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Link: http://lkml.kernel.org/r/20190129150813.15785-1-j.neuschaefer@gmx.netSigned-off-by: NJonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There is a copy and paste bug so we set "config->test_driver" to NULL
twice instead of setting "config->test_fs".  Smatch complains that it
leads to a double free:

  lib/test_kmod.c:840 __kmod_config_init() warn: 'config->test_fs' double freed

Link: http://lkml.kernel.org/r/20190121140011.GA14283@kadam
Fixes: d9c6a72d ("kmod: add test driver to stress test the module loader")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NLuis Chamberlain <mcgrof@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Syzbot instance running on upstream kernel found a use-after-free bug in
oom_kill_process.  On further inspection it seems like the process
selected to be oom-killed has exited even before reaching
read_lock(&tasklist_lock) in oom_kill_process().  More specifically the
tsk->usage is 1 which is due to get_task_struct() in oom_evaluate_task()
and the put_task_struct within for_each_thread() frees the tsk and
for_each_thread() tries to access the tsk.  The easiest fix is to do
get/put across the for_each_thread() on the selected task.

Now the next question is should we continue with the oom-kill as the
previously selected task has exited? However before adding more
complexity and heuristics, let's answer why we even look at the children
of oom-kill selected task? The select_bad_process() has already selected
the worst process in the system/memcg.  Due to race, the selected
process might not be the worst at the kill time but does that matter?
The userspace can use the oom_score_adj interface to prefer children to
be killed before the parent.  I looked at the history but it seems like
this is there before git history.

Link: http://lkml.kernel.org/r/20190121215850.221745-1-shakeelb@google.com
Reported-by: syzbot+7fbbfa368521945f0e3d@syzkaller.appspotmail.com
Fixes: 6b0c81b3 ("mm, oom: reduce dependency on tasklist_lock")
Signed-off-by: NShakeel Butt <shakeelb@google.com>
Reviewed-by: NRoman Gushchin <guro@fb.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

On an arm64 ThunderX2 server, the first kmemleak scan would crash [1]
with CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is
not directly mapped (MEMBLOCK_NOMAP).  Hence, the page->flags is
uninitialized.

This is due to the commit 9f1eb38e ("mm, kmemleak: little
optimization while scanning") starts to use pfn_to_online_page() instead
of pfn_valid().  However, in the CONFIG_MEMORY_HOTPLUG=y case,
pfn_to_online_page() does not call memblock_is_map_memory() while
pfn_valid() does.

Historically, the commit 68709f45 ("arm64: only consider memblocks
with NOMAP cleared for linear mapping") causes pages marked as nomap
being no long reassigned to the new zone in memmap_init_zone() by
calling __init_single_page().

Since the commit 2d070eab ("mm: consider zone which is not fully
populated to have holes") introduced pfn_to_online_page() and was
designed to return a valid pfn only, but it is clearly broken on arm64.

Therefore, let pfn_to_online_page() call pfn_valid_within(), so it can
handle nomap thanks to the commit f52bb98f ("arm64: mm: always
enable CONFIG_HOLES_IN_ZONE"), while it will be optimized away on
architectures where have no HOLES_IN_ZONE.

[1]
  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000006
  Mem abort info:
    ESR = 0x96000005
    Exception class = DABT (current EL), IL = 32 bits
    SET = 0, FnV = 0
    EA = 0, S1PTW = 0
  Data abort info:
    ISV = 0, ISS = 0x00000005
    CM = 0, WnR = 0
  Internal error: Oops: 96000005 [#1] SMP
  CPU: 60 PID: 1408 Comm: kmemleak Not tainted 5.0.0-rc2+ #8
  pstate: 60400009 (nZCv daif +PAN -UAO)
  pc : page_mapping+0x24/0x144
  lr : __dump_page+0x34/0x3dc
  sp : ffff00003a5cfd10
  x29: ffff00003a5cfd10 x28: 000000000000802f
  x27: 0000000000000000 x26: 0000000000277d00
  x25: ffff000010791f56 x24: ffff7fe000000000
  x23: ffff000010772f8b x22: ffff00001125f670
  x21: ffff000011311000 x20: ffff000010772f8b
  x19: fffffffffffffffe x18: 0000000000000000
  x17: 0000000000000000 x16: 0000000000000000
  x15: 0000000000000000 x14: ffff802698b19600
  x13: ffff802698b1a200 x12: ffff802698b16f00
  x11: ffff802698b1a400 x10: 0000000000001400
  x9 : 0000000000000001 x8 : ffff00001121a000
  x7 : 0000000000000000 x6 : ffff0000102c53b8
  x5 : 0000000000000000 x4 : 0000000000000003
  x3 : 0000000000000100 x2 : 0000000000000000
  x1 : ffff000010772f8b x0 : ffffffffffffffff
  Process kmemleak (pid: 1408, stack limit = 0x(____ptrval____))
  Call trace:
   page_mapping+0x24/0x144
   __dump_page+0x34/0x3dc
   dump_page+0x28/0x4c
   kmemleak_scan+0x4ac/0x680
   kmemleak_scan_thread+0xb4/0xdc
   kthread+0x12c/0x13c
   ret_from_fork+0x10/0x18
  Code: d503201f f9400660 36000040 d1000413 (f9400661)
  ---[ end trace 4d4bd7f573490c8e ]---
  Kernel panic - not syncing: Fatal exception
  SMP: stopping secondary CPUs
  Kernel Offset: disabled
  CPU features: 0x002,20000c38
  Memory Limit: none
  ---[ end Kernel panic - not syncing: Fatal exception ]---

Link: http://lkml.kernel.org/r/20190122132916.28360-1-cai@lca.pw
Fixes: 9f1eb38e ("mm, kmemleak: little optimization while scanning")
Signed-off-by: NQian Cai <cai@lca.pw>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This is the same sort of error we saw in commit 17e2e7d7 ("mm,
page_alloc: fix has_unmovable_pages for HugePages").

Gigantic hugepages cross several memblocks, so it can be that the page
we get in scan_movable_pages() is a page-tail belonging to a
1G-hugepage.  If that happens, page_hstate()->size_to_hstate() will
return NULL, and we will blow up in hugepage_migration_supported().

The splat is as follows:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  #PF error: [normal kernel read fault]
  PGD 0 P4D 0
  Oops: 0000 [#1] SMP PTI
  CPU: 1 PID: 1350 Comm: bash Tainted: G            E     5.0.0-rc1-mm1-1-default+ #27
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014
  RIP: 0010:__offline_pages+0x6ae/0x900
  Call Trace:
   memory_subsys_offline+0x42/0x60
   device_offline+0x80/0xa0
   state_store+0xab/0xc0
   kernfs_fop_write+0x102/0x180
   __vfs_write+0x26/0x190
   vfs_write+0xad/0x1b0
   ksys_write+0x42/0x90
   do_syscall_64+0x5b/0x180
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  Modules linked in: af_packet(E) xt_tcpudp(E) ipt_REJECT(E) xt_conntrack(E) nf_conntrack(E) nf_defrag_ipv4(E) ip_set(E) nfnetlink(E) ebtable_nat(E) ebtable_broute(E) bridge(E) stp(E) llc(E) iptable_mangle(E) iptable_raw(E) iptable_security(E) ebtable_filter(E) ebtables(E) iptable_filter(E) ip_tables(E) x_tables(E) kvm_intel(E) kvm(E) irqbypass(E) crct10dif_pclmul(E) crc32_pclmul(E) ghash_clmulni_intel(E) bochs_drm(E) ttm(E) aesni_intel(E) drm_kms_helper(E) aes_x86_64(E) crypto_simd(E) cryptd(E) glue_helper(E) drm(E) virtio_net(E) syscopyarea(E) sysfillrect(E) net_failover(E) sysimgblt(E) pcspkr(E) failover(E) i2c_piix4(E) fb_sys_fops(E) parport_pc(E) parport(E) button(E) btrfs(E) libcrc32c(E) xor(E) zstd_decompress(E) zstd_compress(E) xxhash(E) raid6_pq(E) sd_mod(E) ata_generic(E) ata_piix(E) ahci(E) libahci(E) libata(E) crc32c_intel(E) serio_raw(E) virtio_pci(E) virtio_ring(E) virtio(E) sg(E) scsi_mod(E) autofs4(E)

[akpm@linux-foundation.org: fix brace layout, per David.  Reduce indentation]
Link: http://lkml.kernel.org/r/20190122154407.18417-1-osalvador@suse.deSigned-off-by: NOscar Salvador <osalvador@suse.de>
Reviewed-by: NAnthony Yznaga <anthony.yznaga@oracle.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

psi has provisions to shut off the periodic aggregation worker when
there is a period of no task activity - and thus no data that needs
aggregating.  However, while developing psi monitoring, Suren noticed
that the aggregation clock currently won't stay shut off for good.

Debugging this revealed a flaw in the idle design: an aggregation run
will see no task activity and decide to go to sleep; shortly thereafter,
the kworker thread that executed the aggregation will go idle and cause
a scheduling change, during which the psi callback will kick the
!pending worker again.  This will ping-pong forever, and is equivalent
to having no shut-off logic at all (but with more code!)

Fix this by exempting aggregation workers from psi's clock waking logic
when the state change is them going to sleep.  To do this, tag workers
with the last work function they executed, and if in psi we see a worker
going to sleep after aggregating psi data, we will not reschedule the
aggregation work item.

What if the worker is also executing other items before or after?

Any psi state times that were incurred by work items preceding the
aggregation work will have been collected from the per-cpu buckets
during the aggregation itself.  If there are work items following the
aggregation work, the worker's last_func tag will be overwritten and the
aggregator will be kept alive to process this genuine new activity.

If the aggregation work is the last thing the worker does, and we decide
to go idle, the brief period of non-idle time incurred between the
aggregation run and the kworker's dequeue will be stranded in the
per-cpu buckets until the clock is woken by later activity.  But that
should not be a problem.  The buckets can hold 4s worth of time, and
future activity will wake the clock with a 2s delay, giving us 2s worth
of data we can leave behind when disabling aggregation.  If it takes a
worker more than two seconds to go idle after it finishes its last work
item, we likely have bigger problems in the system, and won't notice one
sample that was averaged with a bogus per-CPU weight.

Link: http://lkml.kernel.org/r/20190116193501.1910-1-hannes@cmpxchg.org
Fixes: eb414681 ("psi: pressure stall information for CPU, memory, and IO")
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Reported-by: NSuren Baghdasaryan <surenb@google.com>
Acked-by: NTejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If memory end is not aligned with the sparse memory section boundary,
the mapping of such a section is only partly initialized.  This may lead
to VM_BUG_ON due to uninitialized struct pages access from
test_pages_in_a_zone() function triggered by memory_hotplug sysfs
handlers.

Here are the the panic examples:
 CONFIG_DEBUG_VM_PGFLAGS=y
 kernel parameter mem=2050M
 --------------------------
 page:000003d082008000 is uninitialized and poisoned
 page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
 Call Trace:
   test_pages_in_a_zone+0xde/0x160
   show_valid_zones+0x5c/0x190
   dev_attr_show+0x34/0x70
   sysfs_kf_seq_show+0xc8/0x148
   seq_read+0x204/0x480
   __vfs_read+0x32/0x178
   vfs_read+0x82/0x138
   ksys_read+0x5a/0xb0
   system_call+0xdc/0x2d8
 Last Breaking-Event-Address:
   test_pages_in_a_zone+0xde/0x160
 Kernel panic - not syncing: Fatal exception: panic_on_oops

Fix this by checking whether the pfn to check is within the zone.

[mhocko@suse.com: separated this change from http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com]
Link: http://lkml.kernel.org/r/20190128144506.15603-3-mhocko@kernel.org

[mhocko@suse.com: separated this change from
http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com]
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NMikhail Zaslonko <zaslonko@linux.ibm.com>
Tested-by: NMikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Reviewed-by: NOscar Salvador <osalvador@suse.de>
Tested-by: NGerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "mm, memory_hotplug: fix uninitialized pages fallouts", v2.

Mikhail Zaslonko has posted fixes for the two bugs quite some time ago
[1].  I have pushed back on those fixes because I believed that it is
much better to plug the problem at the initialization time rather than
play whack-a-mole all over the hotplug code and find all the places
which expect the full memory section to be initialized.

We have ended up with commit 2830bf6f ("mm, memory_hotplug:
initialize struct pages for the full memory section") merged and cause a
regression [2][3].  The reason is that there might be memory layouts
when two NUMA nodes share the same memory section so the merged fix is
simply incorrect.

In order to plug this hole we really have to be zone range aware in
those handlers.  I have split up the original patch into two.  One is
unchanged (patch 2) and I took a different approach for `removable'
crash.

[1] http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1666948
[3] http://lkml.kernel.org/r/20190125163938.GA20411@dhcp22.suse.cz

This patch (of 2):

Mikhail has reported the following VM_BUG_ON triggered when reading sysfs
removable state of a memory block:

 page:000003d08300c000 is uninitialized and poisoned
 page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
 Call Trace:
   is_mem_section_removable+0xb4/0x190
   show_mem_removable+0x9a/0xd8
   dev_attr_show+0x34/0x70
   sysfs_kf_seq_show+0xc8/0x148
   seq_read+0x204/0x480
   __vfs_read+0x32/0x178
   vfs_read+0x82/0x138
   ksys_read+0x5a/0xb0
   system_call+0xdc/0x2d8
 Last Breaking-Event-Address:
   is_mem_section_removable+0xb4/0x190
 Kernel panic - not syncing: Fatal exception: panic_on_oops

The reason is that the memory block spans the zone boundary and we are
stumbling over an unitialized struct page.  Fix this by enforcing zone
range in is_mem_section_removable so that we never run away from a zone.

Link: http://lkml.kernel.org/r/20190128144506.15603-2-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Reported-by: NMikhail Zaslonko <zaslonko@linux.ibm.com>
Debugged-by: NMikhail Zaslonko <zaslonko@linux.ibm.com>
Tested-by: NGerald Schaefer <gerald.schaefer@de.ibm.com>
Tested-by: NMikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Reviewed-by: NOscar Salvador <osalvador@suse.de>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Arkadiusz reported that enabling memcg's group oom killing causes
strange memcg statistics where there is no task in a memcg despite the
number of tasks in that memcg is not 0.  It turned out that there is a
bug in wake_oom_reaper() which allows enqueuing same task twice which
makes impossible to decrease the number of tasks in that memcg due to a
refcount leak.

This bug existed since the OOM reaper became invokable from
task_will_free_mem(current) path in out_of_memory() in Linux 4.7,

  T1@P1     |T2@P1     |T3@P1     |OOM reaper
  ----------+----------+----------+------------
                                   # Processing an OOM victim in a different memcg domain.
                        try_charge()
                          mem_cgroup_out_of_memory()
                            mutex_lock(&oom_lock)
             try_charge()
               mem_cgroup_out_of_memory()
                 mutex_lock(&oom_lock)
  try_charge()
    mem_cgroup_out_of_memory()
      mutex_lock(&oom_lock)
                            out_of_memory()
                              oom_kill_process(P1)
                                do_send_sig_info(SIGKILL, @P1)
                                mark_oom_victim(T1@P1)
                                wake_oom_reaper(T1@P1) # T1@P1 is enqueued.
                            mutex_unlock(&oom_lock)
                 out_of_memory()
                   mark_oom_victim(T2@P1)
                   wake_oom_reaper(T2@P1) # T2@P1 is enqueued.
                 mutex_unlock(&oom_lock)
      out_of_memory()
        mark_oom_victim(T1@P1)
        wake_oom_reaper(T1@P1) # T1@P1 is enqueued again due to oom_reaper_list == T2@P1 && T1@P1->oom_reaper_list == NULL.
      mutex_unlock(&oom_lock)
                                   # Completed processing an OOM victim in a different memcg domain.
                                   spin_lock(&oom_reaper_lock)
                                   # T1P1 is dequeued.
                                   spin_unlock(&oom_reaper_lock)

but memcg's group oom killing made it easier to trigger this bug by
calling wake_oom_reaper() on the same task from one out_of_memory()
request.

Fix this bug using an approach used by commit 855b0183 ("oom,
oom_reaper: disable oom_reaper for oom_kill_allocating_task").  As a
side effect of this patch, this patch also avoids enqueuing multiple
threads sharing memory via task_will_free_mem(current) path.

Link: http://lkml.kernel.org/r/e865a044-2c10-9858-f4ef-254bc71d6cc2@i-love.sakura.ne.jp
Link: http://lkml.kernel.org/r/5ee34fc6-1485-34f8-8790-903ddabaa809@i-love.sakura.ne.jp
Fixes: af8e15cc ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head")
Signed-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: NArkadiusz Miskiewicz <arekm@maven.pl>
Tested-by: NArkadiusz Miskiewicz <arekm@maven.pl>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NRoman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Aleksa Sarai <asarai@suse.de>
Cc: Jay Kamat <jgkamat@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently, buffer_migrate_page_norefs() was constantly failing because
buffer_migrate_lock_buffers() grabbed reference on each buffer.  In
fact, there's no reason for buffer_migrate_lock_buffers() to grab any
buffer references as the page is locked during all our operation and
thus nobody can reclaim buffers from the page.

So remove grabbing of buffer references which also makes
buffer_migrate_page_norefs() succeed.

Link: http://lkml.kernel.org/r/20190116131217.7226-1-jack@suse.cz
Fixes: 89cb0888 "mm: migrate: provide buffer_migrate_page_norefs()"
Signed-off-by: NJan Kara <jack@suse.cz>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently, exit_ptrace() adds all ptraced tasks in a dead list, then
zap_pid_ns_processes() waits on all tasks in a current pidns, and only
then are tasks from the dead list released.

zap_pid_ns_processes() can get stuck on waiting tasks from the dead
list.  In this case, we will have one unkillable process with one or
more dead children.

Thanks to Oleg for the advice to release tasks in find_child_reaper().

Link: http://lkml.kernel.org/r/20190110175200.12442-1-avagin@gmail.com
Fixes: 7c8bd232 ("exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()")
Signed-off-by: NAndrei Vagin <avagin@gmail.com>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If the kernel is configured with KASAN_EXTRA, the stack size is
increasted significantly because this option sets "-fstack-reuse" to
"none" in GCC [1].  As a result, it triggers stack overrun quite often
with 32k stack size compiled using GCC 8.  For example, this reproducer

  https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/madvise/madvise06.c

triggers a "corrupted stack end detected inside scheduler" very reliably
with CONFIG_SCHED_STACK_END_CHECK enabled.

There are just too many functions that could have a large stack with
KASAN_EXTRA due to large local variables that have been called over and
over again without being able to reuse the stacks.  Some noticiable ones
are

  size
  7648 shrink_page_list
  3584 xfs_rmap_convert
  3312 migrate_page_move_mapping
  3312 dev_ethtool
  3200 migrate_misplaced_transhuge_page
  3168 copy_process

There are other 49 functions are over 2k in size while compiling kernel
with "-Wframe-larger-than=" even with a related minimal config on this
machine.  Hence, it is too much work to change Makefiles for each object
to compile without "-fsanitize-address-use-after-scope" individually.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715#c23

Although there is a patch in GCC 9 to help the situation, GCC 9 probably
won't be released in a few months and then it probably take another
6-month to 1-year for all major distros to include it as a default.
Hence, the stack usage with KASAN_EXTRA can be revisited again in 2020
when GCC 9 is everywhere.  Until then, this patch will help users avoid
stack overrun.

This has already been fixed for arm64 for the same reason via
6e883067 ("arm64: kasan: Increase stack size for KASAN_EXTRA").

Link: http://lkml.kernel.org/r/20190109215209.2903-1-cai@lca.pwSigned-off-by: NQian Cai <cai@lca.pw>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

hugetlb needs the same fix as faultin_nopage (which was applied in
commit 96312e61 ("mm/gup.c: teach get_user_pages_unlocked to handle
FOLL_NOWAIT")) or KVM hangs because it thinks the mmap_sem was already
released by hugetlb_fault() if it returned VM_FAULT_RETRY, but it wasn't
in the FOLL_NOWAIT case.

Link: http://lkml.kernel.org/r/20190109020203.26669-2-aarcange@redhat.com
Fixes: ce53053c ("kvm: switch get_user_page_nowait() to get_user_pages_unlocked()")
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Tested-by: N"Dr. David Alan Gilbert" <dgilbert@redhat.com>
Reported-by: N"Dr. David Alan Gilbert" <dgilbert@redhat.com>
Reviewed-by: NMike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: NPeter Xu <peterx@redhat.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>