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Ingo Molnar 6c0398cfeb x86/entry/64: Fix CR3 restore in paranoid_exit() 
commit e486575734 upstream.

Josh Poimboeuf noticed the following bug:

 "The paranoid exit code only restores the saved CR3 when it switches back
  to the user GS.  However, even in the kernel GS case, it's possible that
  it needs to restore a user CR3, if for example, the paranoid exception
  occurred in the syscall exit path between SWITCH_TO_USER_CR3_STACK and
  SWAPGS."

Josh also confirmed via targeted testing that it's possible to hit this bug.

Fix the bug by also restoring CR3 in the paranoid_exit_no_swapgs branch.

The reason we haven't seen this bug reported by users yet is probably because
"paranoid" entry points are limited to the following cases:

 idtentry double_fault       do_double_fault  has_error_code=1  paranoid=2
 idtentry debug              do_debug         has_error_code=0  paranoid=1 shift_ist=DEBUG_STACK
 idtentry int3               do_int3          has_error_code=0  paranoid=1 shift_ist=DEBUG_STACK
 idtentry machine_check      do_mce           has_error_code=0  paranoid=1

Amongst those entry points only machine_check is one that will interrupt an
IRQS-off critical section asynchronously - and machine check events are rare.

The other main asynchronous entries are NMI entries, which can be very high-freq
with perf profiling, but they are special: they don't use the 'idtentry' macro but
are open coded and restore user CR3 unconditionally so don't have this bug.

Reported-and-tested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180214073910.boevmg65upbk3vqb@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2018-02-22 15:42:24 +01:00
arch x86/entry/64: Fix CR3 restore in paranoid_exit() 2018-02-22 15:42:24 +01:00
block blk-mq: quiesce queue before freeing queue 2018-02-16 20:23:09 +01:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK 2018-02-22 15:42:23 +01:00
Documentation kmemcheck: rip it out 2018-02-22 15:42:24 +01:00
drivers x86/cpu: Rename cpu_data.x86_mask to cpu_data.x86_stepping 2018-02-22 15:42:24 +01:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs kmemcheck: remove annotations 2018-02-22 15:42:23 +01:00
include x86/mm: Rename flush_tlb_single() and flush_tlb_one() to __flush_tlb_one_[user|kernel]() 2018-02-22 15:42:24 +01:00
init kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK 2018-02-22 15:42:23 +01:00
ipc License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kernel kmemcheck: rip it out 2018-02-22 15:42:24 +01:00
lib kmemcheck: rip it out 2018-02-22 15:42:24 +01:00
mm kmemcheck: rip it out for real 2018-02-22 15:42:24 +01:00
net kmemcheck: remove annotations 2018-02-22 15:42:23 +01:00
samples samples/bpf: adjust rlimit RLIMIT_MEMLOCK for xdp1 2017-12-20 10:10:31 +01:00
scripts kmemcheck: rip it out 2018-02-22 15:42:24 +01:00
security ima/policy: fix parsing of fsuuid 2018-02-03 17:38:53 +01:00
sound ASoC: skl: Fix kernel warning due to zero NHTL entry 2018-02-16 20:23:04 +01:00
tools selftests/x86/mpx: Fix incorrect bounds with old _sigfault 2018-02-22 15:42:24 +01:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: Handle CPU_PM_ENTER_FAILED 2018-02-16 20:23:03 +01:00
.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: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING [PATCH] update FSF address in COPYING 2005-09-10 10:06:29 -07:00
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS kmemcheck: rip it out 2018-02-22 15:42:24 +01:00
Makefile Linux 4.14.20 2018-02-16 20:23:12 +01:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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.