Merge tag 'perf-urgent-for-mingo-5.0-20190205' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux

 into perf/urgent

Pull perf/urgent fixes from Arnaldo Carvalho de Melo:

perf trace:

  Arnaldo Carvalho de Melo:

    Fix handling of probe:vfs_getname when the probed routine is
    inlined in multiple places, fixing the collection of the 'filename'
    parameter in open syscalls.

perf test:

  Gustavo A. R. Silva:

    Fix bitwise operator usage in evsel-tp-sched test, which made tat
    test always detect fields as signed.

  Jiri Olsa:

    Filter out hidden symbols from labels, added in systems where the
    annobin plugin is used, such as RHEL8, which, if left in place make
    the DWARF unwind 'perf test' to fail on PPC.

  Tony Jones:

    Fix 'perf_event_attr' tests when building with python3.

perf mem/c2c:

  Ravi Bangoria:

    Fix perf_mem_events on PowerPC.

tools headers UAPI:

  Arnaldo Carvalho de Melo:

    Sync linux/in.h copy from the kernel sources, silencing a perf build warning.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Support both Python 2 and Python 3 in tests/attr.py

The use of "except as" syntax implies the minimum supported Python2 version is
now v2.6

Committer testing:

  $ make -C tools/perf PYTHON3=python install-bin

Before:

  # perf test attr
  16: Setup struct perf_event_attr                          : FAILED!
  48: Synthesize attr update                                : Ok
  [root@quaco ~]# perf test -v attr
  16: Setup struct perf_event_attr                          :
  --- start ---
  test child forked, pid 3121
    File "/home/acme/libexec/perf-core/tests/attr.py", line 324
      except Unsup, obj:
                ^
  SyntaxError: invalid syntax
  test child finished with -1
  ---- end ----
  Setup struct perf_event_attr: FAILED!
  48: Synthesize attr update                                :
  --- start ---
  test child forked, pid 3124
  test child finished with 0
  ---- end ----
  Synthesize attr update: Ok
  #

After:

   # perf test attr
  16: Setup struct perf_event_attr                          : Ok
  48: Synthesize attr update                                : Ok
  #

Signed-off-by: Tony Jones <tonyj@suse.de>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Seeteena Thoufeek <s1seetee@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20190124005229.16146-7-tonyj@suse.de


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

With a suitably defined "probe:vfs_getname" probe, 'perf trace' can
"beautify" its output, so syscalls like open() or openat() can print the
"filename" argument instead of just its hex address, like:

  $ perf trace -e open -- touch /dev/null
  [...]
       0.590 ( 0.014 ms): touch/18063 open(filename: /dev/null, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3
  [...]

The output without such beautifier looks like:

     0.529 ( 0.011 ms): touch/18075 open(filename: 0xc78cf288, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3

However, when the vfs_getname probe expands to multiple probes and it is
not the first one that is hit, the beautifier fails, as following:

     0.326 ( 0.010 ms): touch/18072 open(filename: , flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3

Fix it by hooking into all the expanded probes (inlines), now, for instance:

  [root@quaco ~]# perf probe -l
    probe:vfs_getname    (on getname_flags:73@fs/namei.c with pathname)
    probe:vfs_getname_1  (on getname_flags:73@fs/namei.c with pathname)
  [root@quaco ~]# perf trace -e open* sleep 1
       0.010 ( 0.005 ms): sleep/5588 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: RDONLY|CLOEXEC)   = 3
       0.029 ( 0.006 ms): sleep/5588 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: RDONLY|CLOEXEC)   = 3
       0.194 ( 0.008 ms): sleep/5588 openat(dfd: CWD, filename: /usr/lib/locale/locale-archive, flags: RDONLY|CLOEXEC) = 3
  [root@quaco ~]#

Works, further verified with:

  [root@quaco ~]# perf test vfs
  65: Use vfs_getname probe to get syscall args filenames   : Ok
  66: Add vfs_getname probe to get syscall args filenames   : Ok
  67: Check open filename arg using perf trace + vfs_getname: Ok
  [root@quaco ~]#

Reported-by: Michael Petlan <mpetlan@redhat.com>
Tested-by: Michael Petlan <mpetlan@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-mv8kolk17xla1smvmp3qabv1@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

When perf is built with the annobin plugin (RHEL8 build) extra symbols
are added to its binary:

  # nm perf | grep annobin | head -10
  0000000000241100 t .annobin_annotate.c
  0000000000326490 t .annobin_annotate.c
  0000000000249255 t .annobin_annotate.c_end
  00000000003283a8 t .annobin_annotate.c_end
  00000000001bce18 t .annobin_annotate.c_end.hot
  00000000001bce18 t .annobin_annotate.c_end.hot
  00000000001bc3e2 t .annobin_annotate.c_end.unlikely
  00000000001bc400 t .annobin_annotate.c_end.unlikely
  00000000001bce18 t .annobin_annotate.c.hot
  00000000001bce18 t .annobin_annotate.c.hot
  ...

Those symbols have no use for report or annotation and should be
skipped.  Moreover they interfere with the DWARF unwind test on the PPC
arch, where they are mixed with checked symbols and then the test fails:

  # perf test dwarf -v
  59: Test dwarf unwind                                     :
  --- start ---
  test child forked, pid 8515
  unwind: .annobin_dwarf_unwind.c:ip = 0x10dba40dc (0x2740dc)
  ...
  got: .annobin_dwarf_unwind.c 0x10dba40dc, expecting test__arch_unwind_sample
  unwind: failed with 'no error'

The annobin symbols are defined as NOTYPE/LOCAL/HIDDEN:

  # readelf -s ./perf | grep annobin | head -1
    40: 00000000001bce4f     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_init.c

They can still pass the check for the label symbol. Adding check for
HIDDEN and INTERNAL (as suggested by Nick below) visibility and filter
out such symbols.

>   Just to be awkward, if you are going to ignore STV_HIDDEN
>   symbols then you should probably also ignore STV_INTERNAL ones
>   as well...  Annobin does not generate them, but you never know,
>   one day some other tool might create some.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Clifton <nickc@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190128133526.GD15461@krava


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Those aren't present in Alpine Linux 3.4 to edge, so provide fallback
defines to get the next patch building there keeping the build
bisectable.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Clifton <nickc@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/n/tip-03cg3gya2ju4ba2x6ibb9fuz@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

To get the changes in this cset:

  f275ee0f ("IN_BADCLASS: fix macro to actually work")

The macros changed in this cset are not used in tools/, so this is just
to silence this perf tools build warning:

  Warning: Kernel ABI header at 'tools/include/uapi/linux/in.h' differs from latest version at 'include/uapi/linux/in.h'
  diff -u tools/include/uapi/linux/in.h include/uapi/linux/in.h

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-xbk34kwamn8bw8ywpuxetct9@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

It prevents copy elision, generating this warning when building with
fedora:rawhide's clang:

  clang version 7.0.1 (Fedora 7.0.1-2.fc30)
  Target: x86_64-unknown-linux-gnu
  Thread model: posix
  InstalledDir: /usr/bin
  Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
  Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/9
  Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
  Candidate multilib: .;@m64
  Candidate multilib: 32;@m32
  Selected multilib: .;@m64

  $ make -C tools/perf CC=clang LIBCLANGLLVM=1
  <SNIP>
  util/c++/clang.cpp: In function 'std::unique_ptr<llvm::SmallVectorImpl<char> > perf::getBPFObjectFromModule(llvm::Module*)':
  util/c++/clang.cpp:163:18: error: moving a local object in a return statement prevents copy elision [-Werror=pessimizing-move]
    163 |  return std::move(Buffer);
        |         ~~~~~~~~~^~~~~~~~
  util/c++/clang.cpp:163:18: note: remove 'std::move' call
  cc1plus: all warnings being treated as errors
  <SNIP>

References:

  http://www.cplusplus.com/forum/general/186411/#msg908572
  https://en.cppreference.com/w/cpp/language/return#Notes
  https://en.cppreference.com/w/cpp/language/copy_elision

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-lehqf5x5q96l0o8myhb6blz6@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

PowerPC hardware does not have a builtin latency filter (--ldlat) for
the "mem-load" event and perf_mem_events by default includes
"/ldlat=30/" which is causing a failure on PowerPC. Refactor the code to
support "perf mem/c2c" on PowerPC.

This patch depends on kernel side changes done my Madhavan:
https://lists.ozlabs.org/pipermail/linuxppc-dev/2018-December/182596.html



Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Dick Fowles <fowles@inreach.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20190129132412.771-1-ravi.bangoria@linux.ibm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Notice that the use of the bitwise OR operator '|' always leads to true
in this particular case, which seems a bit suspicious due to the context
in which this expression is being used.

Fix this by using bitwise AND operator '&' instead.

This bug was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 6a6cd11d ("perf test: Add test for the sched tracepoint format fields")
Link: http://lkml.kernel.org/r/20190122233439.GA5868@embeddedor


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

The perf tool uses /proc/sys/kernel/perf_event_mlock_kb to determine how
large its ringbuffer mmap should be. This can be configured to arbitrary
values, which can be larger than the maximum possible allocation from
kmalloc.

When this is configured to a suitably large value (e.g. thanks to the
perf fuzzer), attempting to use perf record triggers a WARN_ON_ONCE() in
__alloc_pages_nodemask():

   WARNING: CPU: 2 PID: 5666 at mm/page_alloc.c:4511 __alloc_pages_nodemask+0x3f8/0xbc8

Let's avoid this by checking that the requested allocation is possible
before calling kzalloc.

Reported-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20190110142745.25495-1-mark.rutland@arm.com


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

intel_pmu_cpu_prepare() allocated memory for ->shared_regs among other
members of struct cpu_hw_events. This memory is released in
intel_pmu_cpu_dying() which is wrong. The counterpart of the
intel_pmu_cpu_prepare() callback is x86_pmu_dead_cpu().

Otherwise if the CPU fails on the UP path between CPUHP_PERF_X86_PREPARE
and CPUHP_AP_PERF_X86_STARTING then it won't release the memory but
allocate new memory on the next attempt to online the CPU (leaking the
old memory).
Also, if the CPU down path fails between CPUHP_AP_PERF_X86_STARTING and
CPUHP_PERF_X86_PREPARE then the CPU will go back online but never
allocate the memory that was released in x86_pmu_dying_cpu().

Make the memory allocation/free symmetrical in regard to the CPU hotplug
notifier by moving the deallocation to intel_pmu_cpu_dead().

This started in commit:

   a7e3ed1e

 ("perf: Add support for supplementary event registers").

In principle the bug was introduced in v2.6.39 (!), but it will almost
certainly not backport cleanly across the big CPU hotplug rewrite between v4.7-v4.15...

[ bigeasy: Added patch description. ]
[ mingo: Added backporting guidance. ]

Reported-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> # With developer hat on
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> # With maintainer hat on
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@kernel.org
Cc: bp@alien8.de
Cc: hpa@zytor.com
Cc: jolsa@kernel.org
Cc: kan.liang@linux.intel.com
Cc: namhyung@kernel.org
Cc: <stable@vger.kernel.org>
Fixes: a7e3ed1e ("perf: Add support for supplementary event registers").
Link: https://lkml.kernel.org/r/20181219165350.6s3jvyxbibpvlhtq@linutronix.de


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

Some PCI uncore PMUs cannot be registered on an 8-socket system (HPE
Superdome Flex).

To understand which Socket the PCI uncore PMUs belongs to, perf retrieves
the local Node ID of the uncore device from CPUNODEID(0xC0) of the PCI
configuration space, and the mapping between Socket ID and Node ID from
GIDNIDMAP(0xD4). The Socket ID can be calculated accordingly.

The local Node ID is only available at bit 2:0, but current code doesn't
mask it. If a BIOS doesn't clear the rest of the bits, an incorrect Node ID
will be fetched.

Filter the Node ID by adding a mask.

Reported-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org> # v3.7+
Fixes: 7c94ee2e ("perf/x86: Add Intel Nehalem and Sandy Bridge-EP uncore support")
Link: https://lkml.kernel.org/r/1548600794-33162-1-git-send-email-kan.liang@linux.intel.com


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

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: Qian Cai <cai@lca.pw>
Signed-off-by: Ard 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.org


Signed-off-by: Ingo 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: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Borislav 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-net


Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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-net


Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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.cz


Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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: David Hildenbrand <david@redhat.com>
Reported-by: Vratislav Bendel <vbendel@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Rafael 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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.org


Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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: Michal Hocko <mhocko@suse.com>
Reported-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Tested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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.jp


Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reported-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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.org


Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Link: http://lkml.kernel.org/r/20190129150813.15785-1-j.neuschaefer@gmx.net


Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>