linux.git/Documentation/admin-guide/sysctl, branch v5.11-rc2

Merge tag 'docs-5.11-2' of git://git.lwn.net/linux

2020-12-24T22:20:33+00:00

Pull documentation fixes from Jonathan Corbet:
 "A small set of late-arriving, small documentation fixes"

* tag 'docs-5.11-2' of git://git.lwn.net/linux:
  docs: admin-guide: Fix default value of max_map_count in sysctl/vm.rst
  Documentation/submitting-patches: Document the SoB chain
  Documentation: process: Correct numbering
  docs: submitting-patches: Trivial - fix grammatical error

docs: admin-guide: Fix default value of max_map_count in sysctl/vm.rst

2020-12-21T16:59:07+00:00

Since the default value of sysctl_max_map_count is defined as
DEFAULT_MAX_MAP_COUNT from mm/util.c

    int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;

DEFAULT_MAX_MAP_COUNT is defined as 65530 (65535-5) in include/linux/mm.h

    #define MAPCOUNT_ELF_CORE_MARGIN        (5)
    #define DEFAULT_MAX_MAP_COUNT   (USHRT_MAX - MAPCOUNT_ELF_CORE_MARGIN)

Signed-off-by: Fengfei Xi 
Link: https://lore.kernel.org/r/20201210082134.36957-1-xi.fengfei@h3c.com
Signed-off-by: Jonathan Corbet

Merge branch 'akpm' (patches from Andrew)

2020-12-15T20:53:37+00:00

Merge misc updates from Andrew Morton:

 - a few random little subsystems

 - almost all of the MM patches which are staged ahead of linux-next
   material. I'll trickle to post-linux-next work in as the dependents
   get merged up.

Subsystems affected by this patch series: kthread, kbuild, ide, ntfs,
ocfs2, arch, and mm (slab-generic, slab, slub, dax, debug, pagecache,
gup, swap, shmem, memcg, pagemap, mremap, hmm, vmalloc, documentation,
kasan, pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction,
oom-kill, migration, cma, page-poison, userfaultfd, zswap, zsmalloc,
uaccess, zram, and cleanups).

* emailed patches from Andrew Morton : (200 commits)
  mm: cleanup kstrto*() usage
  mm: fix fall-through warnings for Clang
  mm: slub: convert sysfs sprintf family to sysfs_emit/sysfs_emit_at
  mm: shmem: convert shmem_enabled_show to use sysfs_emit_at
  mm:backing-dev: use sysfs_emit in macro defining functions
  mm: huge_memory: convert remaining use of sprintf to sysfs_emit and neatening
  mm: use sysfs_emit for struct kobject * uses
  mm: fix kernel-doc markups
  zram: break the strict dependency from lzo
  zram: add stat to gather incompressible pages since zram set up
  zram: support page writeback
  mm/process_vm_access: remove redundant initialization of iov_r
  mm/zsmalloc.c: rework the list_add code in insert_zspage()
  mm/zswap: move to use crypto_acomp API for hardware acceleration
  mm/zswap: fix passing zero to 'PTR_ERR' warning
  mm/zswap: make struct kernel_param_ops definitions const
  userfaultfd/selftests: hint the test runner on required privilege
  userfaultfd/selftests: fix retval check for userfaultfd_open()
  userfaultfd/selftests: always dump something in modes
  userfaultfd: selftests: make __{s,u}64 format specifiers portable
  ...

userfaultfd: add user-mode only option to unprivileged_userfaultfd sysctl knob

2020-12-15T20:13:46+00:00

With this change, when the knob is set to 0, it allows unprivileged users
to call userfaultfd, like when it is set to 1, but with the restriction
that page faults from only user-mode can be handled.  In this mode, an
unprivileged user (without SYS_CAP_PTRACE capability) must pass
UFFD_USER_MODE_ONLY to userfaultd or the API will fail with EPERM.

This enables administrators to reduce the likelihood that an attacker with
access to userfaultfd can delay faulting kernel code to widen timing
windows for other exploits.

The default value of this knob is changed to 0.  This is required for
correct functioning of pipe mutex.  However, this will fail postcopy live
migration, which will be unnoticeable to the VM guests.  To avoid this,
set 'vm.userfault = 1' in /sys/sysctl.conf.

The main reason this change is desirable as in the short term is that the
Android userland will behave as with the sysctl set to zero.  So without
this commit, any Linux binary using userfaultfd to manage its memory would
behave differently if run within the Android userland.  For more details,
refer to Andrea's reply [1].

[1] https://lore.kernel.org/lkml/20200904033438.GI9411@redhat.com/

Link: https://lkml.kernel.org/r/20201120030411.2690816-3-lokeshgidra@google.com
Signed-off-by: Lokesh Gidra 
Reviewed-by: Andrea Arcangeli 
Cc: Kees Cook 
Cc: Jonathan Corbet 
Cc: Peter Xu 
Cc: Sebastian Andrzej Siewior 
Cc: Alexander Viro 
Cc: Stephen Smalley 
Cc: Eric Biggers 
Cc: Daniel Colascione 
Cc: "Joel Fernandes (Google)" 
Cc: Kalesh Singh 
Cc: Suren Baghdasaryan 
Cc: Jeff Vander Stoep 
Cc: 
Cc: Mike Rapoport 
Cc: Shaohua Li 
Cc: Jerome Glisse 
Cc: Mauro Carvalho Chehab 
Cc: Johannes Weiner 
Cc: Mel Gorman 
Cc: Nitin Gupta 
Cc: Vlastimil Babka 
Cc: Iurii Zaikin 
Cc: Luis Chamberlain 
Cc: Daniel Colascione 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

docs: Update documentation to reflect what TAINT_CPU_OUT_OF_SPEC means

2020-12-08T17:53:58+00:00

Here's a patch updating the meaning of TAINT_CPU_OUT_OF_SPEC after
Borislav introduced changes in a7e1f67ed29f and upcoming patches in tip.

TAINT_CPU_OUT_OF_SPEC now means a bit more what it implies as the
flag isn't set just because of a CPU misconfiguration or mismatch.
Historically it was for SMP kernel oops on an officially SMP incapable
processor but now it also covers CPUs whose MSRs have been incorrectly
poked at from userspace, drivers being used on non supported
architectures, broken firmware, mismatched CPUs, ...

Update documentation and script to reflect that.

Signed-off-by: Mathieu Chouquet-Stringer 
Link: https://lore.kernel.org/r/20201202153244.709752-1-me@mathieu.digital
Signed-off-by: Jonathan Corbet

Documentation: fix multiple typos found in the admin-guide subdirectory

2020-12-08T17:27:56+00:00

Fix thirty five typos in dm-integrity.rst, dm-raid.rst, dm-zoned.rst,
verity.rst, writecache.rst, tsx_async_abort.rst, md.rst, bttv.rst,
dvb_references.rst, frontend-cardlist.rst, gspca-cardlist.rst, ipu3.rst,
remote-controller.rst, mm/index.rst, numaperf.rst, userfaultfd.rst,
module-signing.rst, imx-ddr.rst, intel-speed-select.rst,
intel_pstate.rst, ramoops.rst, abi.rst, kernel.rst, vm.rst

Signed-off-by: Andrew Klychkov 
Link: https://lore.kernel.org/r/20201204072848.GA49895@spblnx124.lan
Signed-off-by: Jonathan Corbet

docs: clean up sysctl/kernel: titles, version

2020-12-08T17:22:21+00:00

This cleans up a few titles with extra colons, and removes the
reference to kernel 2.2. The docs don't yet cover *all* of 5.10 or
5.11, but I think they're close enough. Most entries are documented,
and have been checked against current kernels.

Signed-off-by: Stephen Kitt 
Link: https://lore.kernel.org/r/20201208074922.30359-1-steve@sk2.org
Signed-off-by: Jonathan Corbet

docs: admin-guide: net.rst: add a missing blank line

2020-10-28T17:26:10+00:00

There's a missing blank line after a literal block, which
causes this warning:

	Documentation/admin-guide/sysctl/net.rst:303: WARNING: Literal block ends without a blank line; unexpected unindent.

Signed-off-by: Mauro Carvalho Chehab 
Link: https://lore.kernel.org/r/b2545be4a4c71269d10278b5990c3e06c4b65f84.1603791716.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet

Merge tag 'docs-5.10-2' of git://git.lwn.net/linux

2020-10-24T00:13:53+00:00

Pull documentation fixes from Jonathan Corbet:
 "A handful of late-arriving documentation fixes"

* tag 'docs-5.10-2' of git://git.lwn.net/linux:
  docs: Add two missing entries in vm sysctl index
  docs/vm: trivial fixes to several spelling mistakes
  docs: submitting-patches: describe preserving review/test tags
  Documentation: Chinese translation of Documentation/arm64/hugetlbpage.rst
  Documentation: x86: fix a missing word in x86_64/mm.rst.
  docs: driver-api: remove a duplicated index entry
  docs: lkdtm: Modernize and improve details
  docs: deprecated.rst: Expand str*cpy() replacement notes
  docs/cpu-load: format the example code.

docs: Add two missing entries in vm sysctl index

2020-10-22T22:11:46+00:00

Both seem overlooked while adding the section in the main content.

Signed-off-by: Fam Zheng 
Link: https://lore.kernel.org/r/20201022065403.3936070-1-fam@euphon.net
Signed-off-by: Jonathan Corbet