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Qian Cai 218209487c mm/swapfile: fix data races in try_to_unuse()
si->inuse_pages could be accessed concurrently as noticed by KCSAN,

 write to 0xffff98b00ebd04dc of 4 bytes by task 82262 on cpu 92:
  swap_range_free+0xbe/0x230
  swap_range_free at mm/swapfile.c:719
  swapcache_free_entries+0x1be/0x250
  free_swap_slot+0x1c8/0x220
  __swap_entry_free.constprop.19+0xa3/0xb0
  free_swap_and_cache+0x53/0xa0
  unmap_page_range+0x7e0/0x1ce0
  unmap_single_vma+0xcd/0x170
  unmap_vmas+0x18b/0x220
  exit_mmap+0xee/0x220
  mmput+0xe7/0x240
  do_exit+0x598/0xfd0
  do_group_exit+0x8b/0x180
  get_signal+0x293/0x13d0
  do_signal+0x37/0x5d0
  prepare_exit_to_usermode+0x1b7/0x2c0
  ret_from_intr+0x32/0x42

 read to 0xffff98b00ebd04dc of 4 bytes by task 82499 on cpu 46:
  try_to_unuse+0x86b/0xc80
  try_to_unuse at mm/swapfile.c:2185
  __x64_sys_swapoff+0x372/0xd40
  do_syscall_64+0x91/0xb05
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The plain reads in try_to_unuse() are outside si->lock critical section
which result in data races that could be dangerous to be used in a loop.
Fix them by adding READ_ONCE().

Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Marco Elver <elver@google.com>
Cc: Hugh Dickins <hughd@google.com>
Link: http://lkml.kernel.org/r/1582578903-29294-1-git-send-email-cai@lca.pw
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-04-02 09:35:27 -07:00
arch asm-generic: make more kernel-space headers mandatory 2020-04-02 09:35:25 -07:00
block Merge branch 'efi-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2020-03-30 16:13:08 -07:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity 2020-02-20 15:15:16 -08:00
Documentation mm: dump_page(): additional diagnostics for huge pinned pages 2020-04-02 09:35:27 -07:00
drivers Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
fs fs_parse: remove pr_notice() about each validation 2020-04-02 09:35:26 -07:00
include mm/gup/writeback: add callbacks for inaccessible pages 2020-04-02 09:35:27 -07:00
init Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-21 11:22:15 -08:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm/swapfile: fix data races in try_to_unuse() 2020-04-02 09:35:27 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
scripts scripts/spelling.txt: add more spellings to spelling.txt 2020-04-02 09:35:25 -07:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
sound Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
tools selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage 2020-04-02 09:35:27 -07:00
usr initramfs: restore default compression behavior 2020-03-17 09:50:37 +09:00
virt irqchip/gic-v4.1: Move doorbell management to the GICv4 abstraction layer 2020-03-24 12:15:51 +00:00
.clang-format clang-format: Update with the latest for_each macro list 2020-03-06 21:50:05 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 selftest/lkdtm: Use local .gitignore 2020-03-02 08:39:39 -07:00
.mailmap media updates for v5.7-rc1 2020-03-30 13:42:05 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Hand MIPS over to Thomas 2020-02-24 22:43:18 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
Makefile Kbuild updates for v5.7 2020-03-31 16:03:39 -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.