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Lars Persson d2b2c6dd22 mm/migrate.c: add missing flush_dcache_page for non-mapped page migrate 
Our MIPS 1004Kc SoCs were seeing random userspace crashes with SIGILL
and SIGSEGV that could not be traced back to a userspace code bug.  They
had all the magic signs of an I/D cache coherency issue.

Now recently we noticed that the /proc/sys/vm/compact_memory interface
was quite efficient at provoking this class of userspace crashes.

Studying the code in mm/migrate.c there is a distinction made between
migrating a page that is mapped at the instant of migration and one that
is not mapped.  Our problem turned out to be the non-mapped pages.

For the non-mapped page the code performs a copy of the page content and
all relevant meta-data of the page without doing the required D-cache
maintenance.  This leaves dirty data in the D-cache of the CPU and on
the 1004K cores this data is not visible to the I-cache.  A subsequent
page-fault that triggers a mapping of the page will happily serve the
process with potentially stale code.

What about ARM then, this bug should have seen greater exposure? Well
ARM became immune to this flaw back in 2010, see commit c01778001a
("ARM: 6379/1: Assume new page cache pages have dirty D-cache").

My proposed fix moves the D-cache maintenance inside move_to_new_page to
make it common for both cases.

Link: http://lkml.kernel.org/r/20190315083502.11849-1-larper@axis.com
Fixes: 97ee052461 ("flush cache before installing new page at migraton")
Signed-off-by: Lars Persson <larper@axis.com>
Reviewed-by: Paul Burton <paul.burton@mips.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-03-29 10:01:37 -07:00
arch s390 update with improvements and bug fixes for 5.1-rc2 2019-03-28 08:35:32 -07:00
block io_uring-20190323 2019-03-23 10:25:12 -07:00
certs kexec, KEYS: Make use of platform keyring for signature verify 2019-02-04 17:34:07 -05:00
crypto lib/lzo: separate lzo-rle from lzo 2019-03-07 18:32:03 -08:00
Documentation vfs: Update mount API docs 2019-03-28 08:54:20 -07:00
drivers drivers/block/zram/zram_drv.c: fix idle/writeback string compare 2019-03-29 10:01:37 -07:00
fs fs/proc/kcore.c: make kcore_modules static 2019-03-29 10:01:37 -07:00
include ptrace: take into account saved_sigmask in PTRACE{GET,SET}SIGMASK 2019-03-29 10:01:37 -07:00
init init/main: add checks for the return value of memblock_alloc*() 2019-03-12 10:04:02 -07:00
ipc Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
kernel ptrace: take into account saved_sigmask in PTRACE{GET,SET}SIGMASK 2019-03-29 10:01:37 -07:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-27 12:22:57 -07:00
LICENSES LICENSES: Add GCC runtime library exception text 2019-01-16 14:54:15 -07:00
mm mm/migrate.c: add missing flush_dcache_page for non-mapped page migrate 2019-03-29 10:01:37 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-27 12:22:57 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-11 08:54:01 -07:00
scripts kconfig: remove stale lxdialog/.gitignore 2019-03-17 15:47:02 +09:00
security selinux: fix NULL dereference in policydb_destroy() 2019-03-18 12:19:48 -04:00
sound sound fixes for 5.1-rc2 2019-03-22 14:04:38 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-27 12:22:57 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt ARM: some cleanups, direct physical timer assignment, cache sanitization 2019-03-15 15:00:28 -07:00
.clang-format Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 13:43:42 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap mailmap: add Changbin Du 2019-03-29 10:01:37 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS io_uring-20190323 2019-03-23 10:25:12 -07:00
Makefile Linux 5.1-rc2 2019-03-24 14:02:26 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.