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From: Kees Cook <keescook@chromium.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Hans de Goede <hdegoede@redhat.com>,
	James Morris <jmorris@namei.org>,
	Mimi Zohar <zohar@linux.ibm.com>,
	Scott Branden <scott.branden@broadcom.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Jessica Yu <jeyu@kernel.org>,
	Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Casey Schaufler <casey@schaufler-ca.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Matthew Garrett <matthewgarrett@google.com>,
	David Howells <dhowells@redhat.com>,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Joel Fernandes (Google)" <joel@joelfernandes.org>,
	KP Singh <kpsingh@google.com>, Dave Olsthoorn <dave@bewaar.me>,
	Peter Jones <pjones@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Stephen Boyd <stephen.boyd@linaro.org>,
	Paul Moore <paul@paul-moore.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org
Subject: Re: [PATCH 0/4] Fix misused kernel_read_file() enums
Date: Wed, 8 Jul 2020 19:00:45 -0700	[thread overview]
Message-ID: <202007081859.A305745@keescook> (raw)
In-Reply-To: <20200708133004.GG4332@42.do-not-panic.com>

On Wed, Jul 08, 2020 at 01:30:04PM +0000, Luis Chamberlain wrote:
> On Wed, Jul 08, 2020 at 01:58:47PM +0200, Hans de Goede wrote:
> > Hi,
> > 
> > On 7/8/20 1:55 PM, Luis Chamberlain wrote:
> > > On Wed, Jul 08, 2020 at 01:37:41PM +0200, Hans de Goede wrote:
> > > > Hi,
> > > > 
> > > > On 7/8/20 1:01 PM, Hans de Goede wrote:
> > > > > Hi,
> > > > > 
> > > > > On 7/7/20 10:19 AM, Kees Cook wrote:
> > > > > > Hi,
> > > > > > 
> > > > > > In looking for closely at the additions that got made to the
> > > > > > kernel_read_file() enums, I noticed that FIRMWARE_PREALLOC_BUFFER
> > > > > > and FIRMWARE_EFI_EMBEDDED were added, but they are not appropriate
> > > > > > *kinds* of files for the LSM to reason about. They are a "how" and
> > > > > > "where", respectively. Remove these improper aliases and refactor the
> > > > > > code to adapt to the changes.
> > > > > > 
> > > > > > Additionally adds in missing calls to security_kernel_post_read_file()
> > > > > > in the platform firmware fallback path (to match the sysfs firmware
> > > > > > fallback path) and in module loading. I considered entirely removing
> > > > > > security_kernel_post_read_file() hook since it is technically unused,
> > > > > > but IMA probably wants to be able to measure EFI-stored firmware images,
> > > > > > so I wired it up and matched it for modules, in case anyone wants to
> > > > > > move the module signature checks out of the module core and into an LSM
> > > > > > to avoid the current layering violations.
> > > > > > 
> > > > > > This touches several trees, and I suspect it would be best to go through
> > > > > > James's LSM tree.
> > > > > > 
> > > > > > Thanks!
> > > > > 
> > > > > 
> > > > > I've done some quick tests on this series to make sure that
> > > > > the efi embedded-firmware support did not regress.
> > > > > That still works fine, so this series is;
> > > > > 
> > > > > Tested-by: Hans de Goede <hdegoede@redhat.com>
> > > > 
> > > > I made a mistake during testing I was not actually running the
> > > > kernel with the patches added.
> > > > 
> > > > After fixing that I did find a problem, patch 4/4:
> > > > "module: Add hook for security_kernel_post_read_file()"
> > > > 
> > > > Breaks module-loading for me. This is with the 4 patches
> > > > on top of 5.8.0-rc4, so this might just be because I'm
> > > > not using the right base.
> > > > 
> > > > With patch 4/4 reverted things work fine for me.
> > > > 
> > > > So, please only add my Tested-by to patches 1-3.
> > > 
> > > BTW is there any testing covered by the selftests for the firmware
> > > laoder which would have caputured this? If not can you extend
> > > it with something to capture this case you ran into?
> > 
> > This was not a firmware-loading issue. For me in my tests,
> > which were limited to 1 device, patch 4/4, which only touches
> > the module-loading code, stopped module loading from working.
> > 
> > Since my test device has / on an eMMC and the kernel config
> > I'm using has mmc-block as a module, things just hung in the
> > initrd since no modules could be loaded, so I did not debug
> > this any further. Dropping  patch 4/4 from my local tree
> > solved this.
> 
> Thanks Hans!
> 
> Kees, would test_kmod.c and the respective selftest would have picked
> this issue up?

I need to check -- I got a (possibly related) 0day report on it too.

Since I have to clean it up further based on Mimi's comments, and adapt
it a bit for Scott's series, I'll need to get a v2 spun for sure. :)

-- 
Kees Cook

      reply	other threads:[~2020-07-09  2:00 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-07  8:19 Kees Cook
2020-07-07  8:19 ` [PATCH 1/4] firmware_loader: EFI firmware loader must handle pre-allocated buffer Kees Cook
2020-07-07  8:19 ` [PATCH 2/4] fs: Remove FIRMWARE_PREALLOC_BUFFER from kernel_read_file() enums Kees Cook
2020-07-07 16:42   ` Scott Branden
2020-07-07 21:55     ` Kees Cook
2020-07-08  3:06       ` Scott Branden
2020-07-08  3:14         ` Kees Cook
2020-07-08  1:37   ` [fs] 676800b78f: BUG:unable_to_handle_page_fault_for_address kernel test robot
2020-07-10 21:00   ` [PATCH 2/4] fs: Remove FIRMWARE_PREALLOC_BUFFER from kernel_read_file() enums Scott Branden
2020-07-10 22:04     ` Matthew Wilcox
2020-07-10 22:10       ` Scott Branden
2020-07-10 22:44         ` Kees Cook
2020-07-10 22:58           ` Scott Branden
2020-07-16 20:35           ` Scott Branden
2020-07-16 21:16             ` Kees Cook
2020-07-07  8:19 ` [PATCH 3/4] fs: Remove FIRMWARE_EFI_EMBEDDED " Kees Cook
2020-07-07  8:19 ` [PATCH 4/4] module: Add hook for security_kernel_post_read_file() Kees Cook
2020-07-08  0:47   ` Mimi Zohar
2020-07-08  3:10     ` Kees Cook
2020-07-08 13:47       ` Mimi Zohar
2020-07-07  9:31 ` [PATCH 0/4] Fix misused kernel_read_file() enums Greg Kroah-Hartman
2020-07-07 15:36 ` Mimi Zohar
2020-07-07 21:45   ` Kees Cook
2020-07-08 11:01 ` Hans de Goede
2020-07-08 11:37   ` Hans de Goede
2020-07-08 11:55     ` Luis Chamberlain
2020-07-08 11:58       ` Hans de Goede
2020-07-08 13:30         ` Luis Chamberlain
2020-07-09  2:00           ` Kees Cook [this message]

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