linux-kernel - Re: [PATCH] ACPI / sysfs: Extend ACPI sysfs to provide access to boot error region

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Date:   Tue, 29 Aug 2017 08:55:56 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Kees Cook <keescook@...gle.com>
Cc:     Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, Boris Petkov <bp@...e.de>,
        Tyler Baicar <tbaicar@...eaurora.org>,
        Punit Agrawal <punit.agrawal@....com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI / sysfs: Extend ACPI sysfs to provide access to
 boot error region

On Mon, Aug 28, 2017 at 05:10:33PM -0700, Kees Cook wrote:
> On Wed, Aug 23, 2017 at 7:56 AM, Luck, Tony <tony.luck@...el.com> wrote:
> >>> Should this not also have a capability check. Assuming file permissions
> >>> are sufficient for grabbing a chunk of system memory holding error
> >>> info doesn't seem too scary but it's at odds with a lot of other cases ?
> >>
> >> At least one of those other cases (pstore) added a capability check and now regret
> >> it.  There's a thread on reverting it. Look for:
> >>
> >>   Revert "pstore: Honor dmesg_restrict sysctl on dmesg dumps"
> >
> > Here's at least part of that thread:
> >
> > https://marc.info/?l=linux-kernel&m=150301241114262&w=2
> >
> > Kees: you were OK with removing the capability check from pstore, right?
> 
> Yeah, as long as there is comparable protections.

File system permission protection is "0400":

	# ls -al /sys/firmware/acpi/tables/data
	total 0
	drwxr-xr-x. 2 root root     0 Aug 28 14:13 .
	drwxr-xr-x. 4 root root     0 Aug 28 14:10 ..
	-r--------. 1 root root 32768 Aug 28 14:13 BERT

-Tony