LKML Archive on
help / color / mirror / Atom feed
From: Andy Lutomirski <>
To: Daniel Micay <>
Cc: Dave Hansen <>,
	Dave Hansen <>,
	kernel list <>,
	Thomas Gleixner <>,
	Ingo Molnar <>, Borislav Petkov <>,
	"H . Peter Anvin" <>, X86 ML <>,
	Peter Zijlstra <>,
	Michael Ellerman <>,
	Will Deacon <>,
	Andy Lutomirski <>,
Subject: Re: [PATCH 1/2] x86/pkeys: copy pkey state at fork()
Date: Fri, 26 Oct 2018 15:12:17 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

> On Oct 26, 2018, at 2:39 PM, Daniel Micay <> wrote:
> I ended up working around this with a pthread_atfork handler disabling
> my usage of the feature in the child process for the time being. I
> don't have an easy way to detect if the bug is present within a
> library so

Can you not just make sure that the fix is backported to all relevant kernels?

I suppose we could add a new flag for pkey_get() or something.

> I'm going to need a kernel version check with a table of
> kernel releases fixing the problem for each stable branch.

That won’t work right on district kernels. Please don’t go there.

> It would be helpful if there was a new cpuinfo flag to check if the
> MPK state is preserved on fork in addition to the existing ospke flag.
> The problem will fade away over time but in my experience there are a
> lot of people using distributions with kernels not incorporating all
> of the stable fixes. I expect other people will run into the problem
> once hardware with MPK is more widely available and other people try
> to use it for various things like moving GC or assorted security
> features. Someone will end up running software adopting it on an older
> kernel with the problem.
> The clobbering issue I found with MAP_FIXED_NOREPLACE isn't quite
> as annoying because it was easy to make a runtime test usable in a library
> to see if the feature works properly.

  reply	other threads:[~2018-10-26 22:12 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-26 19:51 Dave Hansen
2018-10-26 19:51 ` [PATCH 2/2] x86/selftests/pkeys: fork() to check for state being preserved Dave Hansen
2018-10-26 19:59 ` [PATCH 1/2] x86/pkeys: copy pkey state at fork() Dave Hansen
2018-10-26 21:39   ` Daniel Micay
2018-10-26 22:12     ` Andy Lutomirski [this message]
2018-10-26 22:56       ` Daniel Micay
2018-10-29  6:36         ` Ingo Molnar
2018-10-29  8:55           ` Daniel Micay
2018-11-20 21:14   ` Kees Cook
2019-01-09  0:56     ` Kees Cook

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [PATCH 1/2] x86/pkeys: copy pkey state at fork()' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).