linux-kernel - Re: [GIT PULL] hash addresses printed with %p

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Message-ID: <CA+55aFwPXV0sXb+edcQc4epz0pWustZgJsoq95=a3OEDxynq7g@mail.gmail.com>
Date:   Wed, 29 Nov 2017 13:36:25 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Tobin C. Harding" <me@...in.cc>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>
Subject: Re: [GIT PULL] hash addresses printed with %p

On Wed, Nov 29, 2017 at 1:14 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Not because %pK itself changed, but because the semantics of %p did.
> The baseline moved, and the "safe" version did not.

Btw, that baseline for me is now that I can do

  ./scripts/leaking_addresses.pl | wc -l
  18

and of those 18 hits, six are false positives (looks like bitmaps in
the uevent keys).

The remaining 12 are from the EFI runtime map files
(/sys/firmware/efi/runtime-map/*). They should presumably not be
world-readable, but sadly the kset_create_and_add() helper seems to do
that by default.

I think the sysfs code makes it insanely too easy to make things
world-readable. You try to be careful, and mark things read-only etc,
but __ATTR_RO() jkust means S_IRUGO, which means world-readable.

There seems to be no convenient model for kobjects having better
permissions. Greg?

              Linus