linux.git/arch/x86/kernel/msr.c, branch v6.2

driver core: make struct class.devnode() take a const *

2022-11-24T16:12:27+00:00

The devnode() in struct class should not be modifying the device that is
passed into it, so mark it as a const * and propagate the function
signature changes out into all relevant subsystems that use this
callback.

Cc: Fenghua Yu 
Cc: Reinette Chatre 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: x86@kernel.org
Cc: "H. Peter Anvin" 
Cc: FUJITA Tomonori 
Cc: Jens Axboe 
Cc: Justin Sanders 
Cc: Arnd Bergmann 
Cc: Sumit Semwal 
Cc: Benjamin Gaignard 
Cc: Liam Mark 
Cc: Laura Abbott 
Cc: Brian Starkey 
Cc: John Stultz 
Cc: "Christian König" 
Cc: Maarten Lankhorst 
Cc: Maxime Ripard 
Cc: Thomas Zimmermann 
Cc: David Airlie 
Cc: Daniel Vetter 
Cc: Jason Gunthorpe 
Cc: Leon Romanovsky 
Cc: Dennis Dalessandro 
Cc: Dmitry Torokhov 
Cc: Mauro Carvalho Chehab 
Cc: Sean Young 
Cc: Frank Haverkamp 
Cc: Jiri Slaby 
Cc: "Michael S. Tsirkin" 
Cc: Jason Wang 
Cc: Alex Williamson 
Cc: Cornelia Huck 
Cc: Kees Cook 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Tony Luck 
Cc: Jaroslav Kysela 
Cc: Takashi Iwai 
Cc: Hans Verkuil 
Cc: Christophe JAILLET 
Cc: Xie Yongji 
Cc: Gautam Dawar 
Cc: Dan Carpenter 
Cc: Eli Cohen 
Cc: Parav Pandit 
Cc: Maxime Coquelin 
Cc: alsa-devel@alsa-project.org
Cc: dri-devel@lists.freedesktop.org
Cc: kvm@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-block@vger.kernel.org
Cc: linux-input@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-media@vger.kernel.org
Cc: linux-rdma@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Link: https://lore.kernel.org/r/20221123122523.1332370-2-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman

x86/MSR: Filter MSR writes through X86_IOC_WRMSR_REGS ioctl too

2021-01-27T18:06:47+00:00

Commit

  a7e1f67ed29f ("x86/msr: Filter MSR writes")

introduced a module parameter to disable writing to the MSR device file
and tainted the kernel upon writing. As MSR registers can be written by
the X86_IOC_WRMSR_REGS ioctl too, the same filtering and tainting should
be applied to the ioctl as well.

 [ bp: Massage commit message and space out statements. ]

Fixes: a7e1f67ed29f ("x86/msr: Filter MSR writes")
Signed-off-by: Misono Tomohiro 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210127122456.13939-1-misono.tomohiro@jp.fujitsu.com

x86/msr: Add a pointer to an URL which contains further details

2020-12-08T09:17:08+00:00

After having collected the majority of reports about MSRs being written
by userspace tools and what tools those are, and all newer reports
mostly repeating, add an URL where detailed information is gathered and
kept up-to-date.

Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20201205002825.19107-1-bp@alien8.de

x86/msr: Downgrade unrecognized MSR message

2020-11-19T09:46:54+00:00

It is a warning and not an error so use pr_warn().

Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20201118123806.19672-1-bp@alien8.de

x86/msr: Do not allow writes to MSR_IA32_ENERGY_PERF_BIAS

2020-11-16T16:44:04+00:00

Now that all in-kernel-tree users are converted to using the sysfs file,
remove the MSR from the "allowlist".

Signed-off-by: Borislav Petkov 
Reviewed-by: Shuah Khan 
Link: https://lkml.kernel.org/r/20201029190259.3476-5-bp@alien8.de

x86/msr: Make source of unrecognised MSR writes unambiguous

2020-08-22T09:40:38+00:00

In many cases, task_struct.comm isn't enough to distinguish the
offender, since for interpreted languages it's likely just going to be
"python3" or whatever. Add the pid to make it unambiguous.

 [ bp: Make the printk string a single line for easier grepping. ]

Signed-off-by: Chris Down 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/6f6fbd0ee6c99bc5e47910db700a6642159db01b.1598011595.git.chris@chrisdown.name

x86/msr: Prevent userspace MSR access from dominating the console

2020-08-22T09:27:40+00:00

Applications which manipulate MSRs from userspace often do so
infrequently, and all at once. As such, the default printk ratelimit
architecture supplied by pr_err_ratelimited() doesn't do enough to prevent
kmsg becoming completely overwhelmed with their messages and pushing
other salient information out of the circular buffer.

In one case, I saw over 80% of kmsg being filled with these messages,
and the default kmsg buffer being completely filled less than 5 minutes
after boot(!).

Make things much less aggressive, while still achieving the original
goal of fiter_write(). Operators will still get warnings that MSRs are
being manipulated from userspace, but they won't have other also
potentially useful messages pushed out of the kmsg buffer.

Of course, one can boot with `allow_writes=1` to avoid these messages at
all, but that then has the downfall that one doesn't get _any_
notification at all about these problems in the first place, and so is
much less likely to forget to fix it.

One might rather it was less binary: it was still logged, just less
often, so that application developers _do_ have the incentive to improve
their current methods, without the kernel having to push other useful
stuff out of the kmsg buffer.

This one example isn't the point, of course: I'm sure there are plenty
of other non-ideal-but-pragmatic cases where people are writing to MSRs
from userspace right now, and it will take time for those people to find
other solutions.

Overall, keep the intent of the original patch, while mitigating its
sometimes heavy effects on kmsg composition.

[ bp: Massage a bit. ]

Signed-off-by: Chris Down
Signed-off-by: Borislav Petkov
Link: https://lkml.kernel.org/r/563994ef132ce6cffd28fc659254ca37d032b5ef.1598011595.git.chris@chrisdown.name

x86/msr: Filter MSR writes

2020-06-25T08:39:02+00:00

Add functionality to disable writing to MSRs from userspace. Writes can
still be allowed by supplying the allow_writes=on module parameter. The
kernel will be tainted so that it shows in oopses.

Having unfettered access to all MSRs on a system is and has always been
a disaster waiting to happen. Think performance counter MSRs, MSRs with
sticky or locked bits, MSRs making major system changes like loading
microcode, MTRRs, PAT configuration, TSC counter, security mitigations
MSRs, you name it.

This also destroys all the kernel's caching of MSR values for
performance, as the recent case with MSR_AMD64_LS_CFG showed.

Another example is writing MSRs by mistake by simply typing the wrong
MSR address. System freezes have been experienced that way.

In general, poking at MSRs under the kernel's feet is a bad bad idea.

So log writing to MSRs by default. Longer term, such writes will be
disabled by default.

If userspace still wants to do that, then proper interfaces should be
defined which are under the kernel's control and accesses to those MSRs
can be synchronized and sanitized properly.

[ Fix sparse warnings. ]
Reported-by: kernel test robot 
Signed-off-by: Borislav Petkov 
Tested-by: Sean Christopherson 
Link: https://lkml.kernel.org/r/20200612105026.GA22660@zn.tnic

x86/msr: Restrict MSR access when the kernel is locked down

2019-08-20T04:54:16+00:00

Writing to MSRs should not be allowed if the kernel is locked down, since
it could lead to execution of arbitrary code in kernel mode.  Based on a
patch by Kees Cook.

Signed-off-by: Matthew Garrett 
Signed-off-by: David Howells 
Acked-by: Kees Cook 
Reviewed-by: Thomas Gleixner 
cc: x86@kernel.org
Signed-off-by: James Morris

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 142

2019-05-30T18:25:17+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation inc 675 mass ave cambridge ma 02139 usa
  either version 2 of the license or at your option any later version
  incorporated herein by reference

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 4 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Richard Fontana 
Reviewed-by: Allison Randal 
Reviewed-by: Kate Stewart 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190524100844.465381181@linutronix.de
Signed-off-by: Greg Kroah-Hartman