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Nicholas Piggin b65458b6be powerpc/64s: flush L1D on kernel entry
commit f79643787e upstream.

[backporting note: we need to mark some exception handlers as out-of-line
 because the flushing makes them take too much space -- dja]

IBM Power9 processors can speculatively operate on data in the L1 cache
before it has been completely validated, via a way-prediction mechanism. It
is not possible for an attacker to determine the contents of impermissible
memory using this method, since these systems implement a combination of
hardware and software security measures to prevent scenarios where
protected data could be leaked.

However these measures don't address the scenario where an attacker induces
the operating system to speculatively execute instructions using data that
the attacker controls. This can be used for example to speculatively bypass
"kernel user access prevention" techniques, as discovered by Anthony
Steinhauser of Google's Safeside Project. This is not an attack by itself,
but there is a possibility it could be used in conjunction with
side-channels or other weaknesses in the privileged code to construct an
attack.

This issue can be mitigated by flushing the L1 cache between privilege
boundaries of concern. This patch flushes the L1 cache on kernel entry.

This is part of the fix for CVE-2020-4788.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-11-22 10:14:10 +01:00
Documentation powerpc/64s: flush L1D on kernel entry 2020-11-22 10:14:10 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch powerpc/64s: flush L1D on kernel entry 2020-11-22 10:14:10 +01:00
block blk-cgroup: Pre-allocate tree node on blkg_conf_prep 2020-11-10 12:37:30 +01:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: algif_skcipher - EBUSY on aio should be an error 2020-10-29 09:57:30 +01:00
drivers drm/i915: Correctly set SFC capability for video engines 2020-11-18 19:20:33 +01:00
fs Convert trailing spaces and periods in path components 2020-11-18 19:20:34 +01:00
include SUNRPC: Fix general protection fault in trace_rpc_xdr_overflow() 2020-11-18 19:20:26 +01:00
init printk: reduce LOG_BUF_SHIFT range for H8300 2020-11-05 11:43:16 +01:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel perf/core: Fix race in the perf_mmap_close() function 2020-11-18 19:20:33 +01:00
lib random32: make prandom_u32() output unpredictable 2020-11-18 19:20:20 +01:00
mm mm/slub: fix panic in slab_alloc_node() 2020-11-18 19:20:30 +01:00
net net: sch_generic: fix the missing new qdisc assignment bug 2020-11-18 19:20:33 +01:00
samples samples/bpf: Fix possible deadlock in xdpsock 2020-11-05 11:43:17 +01:00
scripts scripts/setlocalversion: make git describe output more reliable 2020-11-01 12:01:01 +01:00
security selinux: Fix error return code in sel_ib_pkey_sid_slow() 2020-11-18 19:20:30 +01:00
sound ALSA: hda: Reinstate runtime_allow() for all hda controllers 2020-11-18 19:20:22 +01:00
tools selftests/powerpc: rfi_flush: disable entry flush if present 2020-11-22 10:14:10 +01:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: ARM_SMCCC_ARCH_WORKAROUND_1 doesn't return SMCCC_RET_NOT_REQUIRED 2020-11-18 19:20:21 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.78 2020-11-18 19:20:34 +01:00
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.