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Filename Latest commit message Latest commit date
Borislav Petkov 6827d62a86 x86/mce: Make mce_rdmsrl() panic on an inaccessible MSR
[ Upstream commit e2def7d49d0812ea40a224161b2001b2e815dce2 ]

If an exception needs to be handled while reading an MSR - which is in
most of the cases caused by a #GP on a non-existent MSR - then this
is most likely the incarnation of a BIOS or a hardware bug. Such bug
violates the architectural guarantee that MCA banks are present with all
MSRs belonging to them.

The proper fix belongs in the hardware/firmware - not in the kernel.

Handling an #MC exception which is raised while an NMI is being handled
would cause the nasty NMI nesting issue because of the shortcoming of
IRET of reenabling NMIs when executed. And the machine is in an #MC
context already so <Deity> be at its side.

Tracing MSR accesses while in #MC is another no-no due to tracing being
inherently a bad idea in atomic context:

  vmlinux.o: warning: objtool: do_machine_check()+0x4a: call to mce_rdmsrl() leaves .noinstr.text section

so remove all that "additional" functionality from mce_rdmsrl() and
provide it with a special exception handler which panics the machine
when that MSR is not accessible.

The exception handler prints a human-readable message explaining what
the panic reason is but, what is more, it panics while in the #GP
handler and latter won't have executed an IRET, thus opening the NMI
nesting issue in the case when the #MC has happened while handling
an NMI. (#MC itself won't be reenabled until MCG_STATUS hasn't been
cleared).

Suggested-by: Andy Lutomirski <luto@kernel.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
[ Add missing prototypes for ex_handler_* ]
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20200906212130.GA28456@zn.tnic
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-10-29 09:58:03 +01:00
arch x86/mce: Make mce_rdmsrl() panic on an inaccessible MSR 2020-10-29 09:58:03 +01:00
block block: ratelimit handle_bad_sector() message 2020-10-29 09:58:01 +01:00
certs
crypto crypto: algif_skcipher - EBUSY on aio should be an error 2020-10-29 09:57:30 +01:00
Documentation x86/fpu: Allow multiple bits in clearcpuid= parameter 2020-10-29 09:57:29 +01:00
drivers media: media/pci: prevent memory leak in bttv_probe 2020-10-29 09:58:02 +01:00
fs ext4: limit entries returned when counting fsmap records 2020-10-29 09:57:55 +01:00
include perf: correct SNOOPX field offset 2020-10-29 09:58:00 +01:00
init kprobes: tracing/kprobes: Fix to kill kprobes on initmem after boot 2020-10-01 13:18:23 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel sched/features: Fix !CONFIG_JUMP_LABEL case 2020-10-29 09:58:00 +01:00
lib lib/crc32.c: fix trivial typo in preprocessor condition 2020-10-29 09:57:52 +01:00
LICENSES
mm mm/page_owner: change split_page_owner to take a count 2020-10-29 09:57:52 +01:00
net netfilter: nf_fwd_netdev: clear timestamp in forwarding path 2020-10-29 09:57:57 +01:00
samples bpf: Fix fds_example SIGSEGV error 2020-08-19 08:16:03 +02:00
scripts scripts/dtc: only append to HOST_EXTRACFLAGS instead of overwriting 2020-10-07 08:01:29 +02:00
security ima: Don't ignore errors from crypto_shash_update() 2020-10-29 09:57:28 +01:00
sound ASoC: fsl_sai: Instantiate snd_soc_dai_driver 2020-10-29 09:57:42 +01:00
tools selftests/powerpc: Fix eeh-basic.sh exit codes 2020-10-29 09:57:52 +01:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch 2020-10-01 13:18:25 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.72 2020-10-17 10:11:24 +02:00
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.