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Filename Latest commit message Latest commit date
Jane Malalane 7252cb96e4 x86/cpu: Fix migration safety with X86_BUG_NULL_SEL
commit 415de44076640483648d6c0f6d645a9ee61328ad upstream.

Currently, Linux probes for X86_BUG_NULL_SEL unconditionally which
makes it unsafe to migrate in a virtualised environment as the
properties across the migration pool might differ.

To be specific, the case which goes wrong is:

1. Zen1 (or earlier) and Zen2 (or later) in a migration pool
2. Linux boots on Zen2, probes and finds the absence of X86_BUG_NULL_SEL
3. Linux is then migrated to Zen1

Linux is now running on a X86_BUG_NULL_SEL-impacted CPU while believing
that the bug is fixed.

The only way to address the problem is to fully trust the "no longer
affected" CPUID bit when virtualised, because in the above case it would
be clear deliberately to indicate the fact "you might migrate to
somewhere which has this behaviour".

Zen3 adds the NullSelectorClearsBase CPUID bit to indicate that loading
a NULL segment selector zeroes the base and limit fields, as well as
just attributes. Zen2 also has this behaviour but doesn't have the NSCB
bit.

 [ bp: Minor touchups. ]

Signed-off-by: Jane Malalane <jane.malalane@citrix.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
CC: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20211021104744.24126-1-jane.malalane@citrix.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-11-17 09:48:19 +01:00
arch x86/cpu: Fix migration safety with X86_BUG_NULL_SEL 2021-11-17 09:48:19 +01:00
block Revert "block, bfq: honor already-setup queue merges" 2021-10-06 15:42:34 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:47:29 +02:00
crypto crypto: shash - avoid comparing pointers to exported functions under CFI 2021-07-14 16:53:13 +02:00
Documentation dt-bindings: mtd: gpmc: Fix the ECC bytes vs. OOB bytes equation 2021-09-22 12:26:43 +02:00
drivers media: v4l2-ioctl: Fix check_ext_ctrls 2021-11-17 09:48:18 +01:00
fs fuse: fix page stealing 2021-11-17 09:48:19 +01:00
include libata: fix read log timeout value 2021-11-17 09:48:17 +01:00
init kbuild: add CONFIG_LD_IS_LLD 2021-06-30 08:47:44 -04:00
ipc
kernel printk/console: Allow to disable console output by using console="" or console=null 2021-11-12 14:43:03 +01:00
lib Kconfig.debug: drop selecting non-existing HARDLOCKUP_DETECTOR_ARCH 2021-09-26 14:07:10 +02:00
LICENSES
mm mm, slub: fix potential memoryleak in kmem_cache_open() 2021-10-27 09:54:28 +02:00
net cfg80211: correct bridge/4addr mode check 2021-11-02 19:46:15 +01:00
samples samples: bpf: Fix tracex7 error raised on the missing argument 2021-09-22 12:26:30 +02:00
scripts gcc-plugins/structleak: add makefile var for disabling structleak 2021-10-27 09:54:28 +02:00
security binder: use cred instead of task for selinux checks 2021-11-17 09:48:16 +01:00
sound ALSA: timer: Unconditionally unlink slave instances, too 2021-11-17 09:48:19 +01:00
tools perf script: Check session->header.env.arch before using it 2021-11-02 19:46:15 +01:00
usr
virt KVM: do not shrink halt_poll_ns below grow_start 2021-10-09 14:39:50 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile Linux 5.4.159 2021-11-12 14:43:05 +01:00
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.