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Tony Luck fd0e786d9d x86/mm, mm/hwpoison: Don't unconditionally unmap kernel 1:1 pages 
In the following commit:

  ce0fa3e56a ("x86/mm, mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages")

... we added code to memory_failure() to unmap the page from the
kernel 1:1 virtual address space to avoid speculative access to the
page logging additional errors.

But memory_failure() may not always succeed in taking the page offline,
especially if the page belongs to the kernel.  This can happen if
there are too many corrected errors on a page and either mcelog(8)
or drivers/ras/cec.c asks to take a page offline.

Since we remove the 1:1 mapping early in memory_failure(), we can
end up with the page unmapped, but still in use. On the next access
the kernel crashes :-(

There are also various debug paths that call memory_failure() to simulate
occurrence of an error. Since there is no actual error in memory, we
don't need to map out the page for those cases.

Revert most of the previous attempt and keep the solution local to
arch/x86/kernel/cpu/mcheck/mce.c. Unmap the page only when:

	1) there is a real error
	2) memory_failure() succeeds.

All of this only applies to 64-bit systems. 32-bit kernel doesn't map
all of memory into kernel space. It isn't worth adding the code to unmap
the piece that is mapped because nobody would run a 32-bit kernel on a
machine that has recoverable machine checks.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave <dave.hansen@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert (Persistent Memory) <elliott@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Cc: stable@vger.kernel.org #v4.14
Fixes: ce0fa3e56a ("x86/mm, mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-02-13 16:25:06 +01:00
arch x86/mm, mm/hwpoison: Don't unconditionally unmap kernel 1:1 pages 2018-02-13 16:25:06 +01:00
block for-linus-20180204 2018-02-04 11:16:35 -08:00
certs
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-01-31 14:22:45 -08:00
Documentation Merge branch 'idr-2018-02-06' of git://git.infradead.org/users/willy/linux-dax 2018-02-08 14:39:29 -08:00
drivers IOMMU Updates for Linux v4.16 2018-02-08 12:03:54 -08:00
firmware
fs vfs/proc/kcore, x86/mm/kcore: Fix SMAP fault when dumping vsyscall user page 2018-02-13 09:15:58 +01:00
include x86/mm, mm/hwpoison: Don't unconditionally unmap kernel 1:1 pages 2018-02-13 16:25:06 +01:00
init membarrier: Provide core serializing command, *_SYNC_CORE 2018-02-05 21:35:03 +01:00
ipc ipc/mqueue.c: have RT tasks queue in by priority in wq_add() 2018-02-06 18:32:46 -08:00
kernel Modules updates for v4.16 2018-02-07 14:29:34 -08:00
lib Merge branch 'idr-2018-02-06' of git://git.infradead.org/users/willy/linux-dax 2018-02-08 14:39:29 -08:00
LICENSES LICENSES: Add MPL-1.1 license 2018-01-06 10:59:44 -07:00
mm x86/mm, mm/hwpoison: Don't unconditionally unmap kernel 1:1 pages 2018-02-13 16:25:06 +01:00
net This request is late, apologies. 2018-02-08 15:18:32 -08:00
samples sample/bpf: fix erspan metadata 2018-02-06 11:32:49 -05:00
scripts - update includes for gcc 8 (Valdis Kletnieks) 2018-02-08 14:37:32 -08:00
security iversion.h related cleanup for v4.16 2018-02-07 14:25:22 -08:00
sound ASoC: Updates for v4.16 2018-02-07 12:11:09 -08:00
tools Merge branch 'idr-2018-02-06' of git://git.infradead.org/users/willy/linux-dax 2018-02-08 14:39:29 -08:00
usr
virt 2nd set of arm64 updates for 4.16: 2018-02-08 10:44:25 -08:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap mailmap: update Mark Yao's email address 2018-01-04 16:45:09 -08:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Mostly cleanups, but three bug fixes: 2018-02-08 12:20:41 -08:00
Makefile Makefile: introduce CONFIG_CC_STACKPROTECTOR_AUTO 2018-02-06 18:32:44 -08:00
README

README 

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.