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Huang Ying aeb309b81c mm/mincore.c: fix race between swapoff and mincore 
Via commit 4b3ef9daa4 ("mm/swap: split swap cache into 64MB trunks"),
after swapoff, the address_space associated with the swap device will be
freed.  So swap_address_space() users which touch the address_space need
some kind of mechanism to prevent the address_space from being freed
during accessing.

When mincore processes an unmapped range for swapped shmem pages, it
doesn't hold the lock to prevent swap device from being swapped off.  So
the following race is possible:

CPU1					CPU2
do_mincore()				swapoff()
  walk_page_range()
    mincore_unmapped_range()
      __mincore_unmapped_range
        mincore_page
	  as = swap_address_space()
          ...				  exit_swap_address_space()
          ...				    kvfree(spaces)
	  find_get_page(as)

The address space may be accessed after being freed.

To fix the race, get_swap_device()/put_swap_device() is used to enclose
find_get_page() to check whether the swap entry is valid and prevent the
swap device from being swapoff during accessing.

Link: http://lkml.kernel.org/r/20190611020510.28251-1-ying.huang@intel.com
Fixes: 4b3ef9daa4 ("mm/swap: split swap cache into 64MB trunks")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-12 11:05:43 -07:00
arch sparc: remove ARCH_SELECT_MEMORY_MODEL 2019-07-12 11:05:42 -07:00
block for-5.3/block-20190708 2019-07-09 10:45:06 -07:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2019-07-08 20:57:08 -07:00
Documentation mm, debug_pagealloc: use a page type instead of page_ext flag 2019-07-12 11:05:43 -07:00
drivers lkdtm/heap: add tests for freelist hardening 2019-07-12 11:05:41 -07:00
fs 9p: pass the correct prototype to read_cache_page 2019-07-12 11:05:43 -07:00
include mm, swap: use rbtree for swap_extent 2019-07-12 11:05:43 -07:00
init It's been a relatively busy cycle for docs: 2019-07-09 12:34:26 -07:00
ipc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
kernel mm/nvdimm: add is_ioremap_addr and use that to check ioremap address 2019-07-12 11:05:40 -07:00
lib lib/test_kasan: Add test for double-kzfree detection 2019-07-12 11:05:42 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm/mincore.c: fix race between swapoff and mincore 2019-07-12 11:05:43 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-07-11 10:55:49 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-07-11 10:55:49 -07:00
scripts scripts/spelling.txt: add more spellings to spelling.txt 2019-07-12 11:05:41 -07:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-07-11 10:55:49 -07:00
sound It's been a relatively busy cycle for docs: 2019-07-09 12:34:26 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-07-11 10:55:49 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt SPDX update for 5.2-rc6 2019-06-21 09:58:42 -07:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes
.gitignore .gitignore: exclude .get_maintainer.ignore and .gitattributes 2019-05-18 11:49:54 +09:00
.mailmap MAINTAINERS: Update my email address 2019-06-18 14:37:27 +01:00
COPYING
CREDITS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-06-25 01:32:59 +02:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: nilfs2: update email address 2019-07-12 11:05:40 -07:00
Makefile Linux 5.2 2019-07-07 15:41:56 -07:00
README

README 

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.