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Qian Cai a1f459354a mm/list_lru: fix a data race in list_lru_count_one
struct list_lru_one l.nr_items could be accessed concurrently as noticed
by KCSAN,

 BUG: KCSAN: data-race in list_lru_count_one / list_lru_isolate_move

 write to 0xffffa102789c4510 of 8 bytes by task 823 on cpu 39:
  list_lru_isolate_move+0xf9/0x130
  list_lru_isolate_move at mm/list_lru.c:180
  inode_lru_isolate+0x12b/0x2a0
  __list_lru_walk_one+0x122/0x3d0
  list_lru_walk_one+0x75/0xa0
  prune_icache_sb+0x8b/0xc0
  super_cache_scan+0x1b8/0x250
  do_shrink_slab+0x256/0x6d0
  shrink_slab+0x41b/0x4a0
  shrink_node+0x35c/0xd80
  balance_pgdat+0x652/0xd90
  kswapd+0x396/0x8d0
  kthread+0x1e0/0x200
  ret_from_fork+0x27/0x50

 read to 0xffffa102789c4510 of 8 bytes by task 6345 on cpu 56:
  list_lru_count_one+0x116/0x2f0
  list_lru_count_one at mm/list_lru.c:193
  super_cache_count+0xe8/0x170
  do_shrink_slab+0x95/0x6d0
  shrink_slab+0x41b/0x4a0
  shrink_node+0x35c/0xd80
  do_try_to_free_pages+0x1f7/0xa10
  try_to_free_pages+0x26c/0x5e0
  __alloc_pages_slowpath+0x458/0x1290
  __alloc_pages_nodemask+0x3bb/0x450
  alloc_pages_vma+0x8a/0x2c0
  do_anonymous_page+0x170/0x700
  __handle_mm_fault+0xc9f/0xd00
  handle_mm_fault+0xfc/0x2f0
  do_page_fault+0x263/0x6f9
  page_fault+0x34/0x40

 Reported by Kernel Concurrency Sanitizer on:
 CPU: 56 PID: 6345 Comm: oom01 Tainted: G        W    L 5.5.0-next-20200205+ #4
 Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019

A shattered l.nr_items could affect the shrinker behaviour due to a data
race. Fix it by adding READ_ONCE() for the read. Since the writes are
aligned and up to word-size, assume those are safe from data races to
avoid readability issues of writing WRITE_ONCE(var, var + val).

Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Marco Elver <elver@google.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Link: http://lkml.kernel.org/r/1581114679-5488-1-git-send-email-cai@lca.pw
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-14 19:56:57 -07:00
arch all arch: remove system call sys_sysctl 2020-08-14 19:56:56 -07:00
block A set of locking fixes and updates: 2020-08-10 19:07:44 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-08-14 13:09:15 -07:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-13 20:03:11 -07:00
drivers mm: add thp_size 2020-08-14 19:56:56 -07:00
fs fs: autofs: delete repeated words in comments 2020-08-14 19:56:56 -07:00
include mm/memcontrol: fix a data race in scan count 2020-08-14 19:56:57 -07:00
init OpenRISC updates for 5.9 2020-08-14 14:04:53 -07:00
ipc ipc/shm.c: remove the superfluous break 2020-08-12 10:58:02 -07:00
kernel all arch: remove system call sys_sysctl 2020-08-14 19:56:56 -07:00
lib lz4: fix kernel decompression speed 2020-08-14 19:56:56 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm/list_lru: fix a data race in list_lru_count_one 2020-08-14 19:56:57 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-13 20:03:11 -07:00
samples Kbuild updates for v5.9 2020-08-09 14:10:26 -07:00
scripts Kconfig updates for v5.9 2020-08-14 11:04:45 -07:00
security Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
sound sound updates for 5.9 2020-08-06 14:27:31 -07:00
tools all arch: remove system call sys_sysctl 2020-08-14 19:56:56 -07:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: Add ZSTD-compressed files 2020-07-31 11:50:49 +02:00
.mailmap mailmap: add entry for Greg Kurz 2020-08-14 19:56:56 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Replace HTTP links with HTTPS ones 2020-07-23 14:53:58 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-13 20:03:11 -07:00
Makefile ./Makefile: add debug option to enable function aligned on 32 bytes 2020-08-12 10:57:59 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.